Bacterial Cells Flashcards
How do lysozymes inhibit cell wall formation in bacteria?
Degrades the structural integrity of cell wall peptidoglycan. It breaks the B 1,4- bonds of the glycan portion of the peptidoglycan
Lysozymes can be found in body fluids (tears, saliva, blood, and breast milk
Cytoplasmic granules contain ____________
glycogen
Rifampin treats____________
Tuberculosis
_______________ is one transcription factor that activates the expression of virulence
genes at 37 degrees Celsius (body temp of host).
PrfA
Site of protein synthesis in bacteria
Poly ribosomes
B-lactams
Types: penicillins,cephalosporins,cephamycins,carbapenems,
monobactams
inhibit enzymes (PBPs) which catalyze the transpeptide linkage; inhibition results in autolytic enzyme accumulation and lysis
Resitance:
- Production of beta-lactamases
- Failure to penetrate outer membrane
- Mutation in penicillin-binding proteins
Lipid found in the cytoplasmic membrane of the inner leaflet
Phosphotidyl ethanolamine
Mobile genetic elements
Also known as jumping genes
- *- They have ability to insert as discrete DNA segments
- They randomly insert into whatever chromosome they choose
- They’re natural constituents of prokaryotic chromosomes/plasmids
- They’ve been found in bacteriophage DNA as well as eukaryotic cells**
Types
1. Insertional elements
2. Transposoons
• Before the bacteria can establish colonization, it must have _____________factors.
adherent
Model for CAP (CRP) activation of the Lac operon
Optimal activation of the lac operon requires both
1)The inducer (lactose)
to bind the lac repressor (De-repression) in order
to release repressor from DNA.
2) The activator (cAMP-CRP) to bind – (Induction) to the CAP site
●
Bacterial Toxins
- Endotoxins (LPS)
- Exotoxins
HPV 16/18 Ribozymes
Ribozyme can be made specifically to recognize and attack a specific mRNA. All the human papilloma virus that are known to be involved in cancer formation express E6 protein and the E7 protein.
If you make an E7 specific ribozyme and place it in a cell with HPV16 or HPV18 present, this E7 ribozyme will bind to the E7 mRNA and digest it to the point where it cannot be translated. You end up having no E7 protein and NO transformation to the cancer phenotype.
▪
□ THIS is the basis of the HPV vaccine.
Antibiotic inhibitors of protein synthesis
30S
-
Aminoglycosides
- __Gentamycin
- Steptomycin
- Tobramycin
-
Tetracyclines
- __Tetracycline
- Docycycline
50 S
- Chloramphenicol
- Lincosamides
- Erythromycin
- Fusidic acid
Determinants of Pathogenicity
- Bacterial adherence & Intracellular Growth
- Tissue specificity
- Invasiveness
- Toxins
- Antiphagocytic factors
- Immune complex formation
- Resistance to complement damage
- Siderophore production
- Antigenic variation
- Proteolysis of antibodies
- Plasmids
Acute-phase protein
a class of proteins whose plasma concentrations increase (positive acute-phaseproteins) or decrease (negative acute-phase proteins) in response to inflammation
Tissue Affinity Examples
•Streptococcus mutans
–tooth enamel
•Streptococcus salivarius
–surface of tongue
•Streptococcus pyogenes
–pharyngeal epithelium
Transcriptional control by use of alternative sigma factors
You have RNA polymerase, which is an alpha, beta subunit
But, when you add a sigma factor to it, you have a holoenzyme for RNA
polymerase
•
• The sigma factor determines promoter specificity of RNA polymerase
You change the sigma factor, you change the promoter that is being
• Sigma factors can even influence sporulation during starvation
You actually have different sigma factors being turned on to develop this
endospore
actively transcribed at any one time
•
Antibiotics that inhibit cell wall synthesis
B-lactams
Vancomycin
Isoniazid
Ethambutol
Cycloserine
Ethionamide
Bacitracin
Polymyxin
Daptomycin
How do extracellular infectious agents cause disease?
They cause disease by invasion of host tissue, inducing inflammation or by liberation of toxins without invasion or both
Virus infections have an extracellular phase at which time they are vulnerable to the host antibody responses
Diauxic growth
any cell growth characterized by cellular growth in two phases, and can be illustrated with adiauxic growth curve.
E. Coli use glucose more rapidly than lactose. When they both grow at the same time, that is called diauxic growth. There will be two exponential period. 1st exp, then lag, 2nd exp, then another lag. This is called a diauxic shift.
Overgrowth of clostridium difficile can cause?
Pseudomembranous colitis
Caused by excessive antibiotic use (such as clindamycin, which treats candida albicans)
metronidazole effective
____________ enhances mobility.
Flagella
Components of LPS
Lipid A
Core polysaccharide
O antigen
Listeria monocytogenes is a human pathogenic bacterium that causes ______________
food poisoning.
Prokaryotes that are pathogenic to us
E. coli
Salmonella species (gastroenteritis)
Streptococcus pyogenes (pharyngitis)
HIV
influenza viruses
EBV
HPV
CAP (Catabolic Activator Protein)
Catabolic Activator Protein (CAP) or cyclic AMP Receptor Protein (CRP) is a Positive regulator of lac transcription.
- CAP is a pleiotropic or general activator. It functions at many different promoters, not just lac.
- CAP is a sequence-specific DNA binding protein
- CAP responds to cAMP levels in the cell. cAMP-CAP binding is equired for high expression of the lac operon. This conserves the cells energy.
Pilli
Used for attachment to host cell
Transfer of DNA from bacterial organisms to another
Found mostly in gram negative bacteria
pili also carry surface antigens, which may be responsible for the virulous of the bacteria and for the pathogenicity of the bacteria
Mode of action for protein synthesis inhibition
Some bacteria can inhibit protein synthesis by inhibiting the elongation factor in the protein
machinery
○Inhibiting the elongation factor prevents peptide bond formation between the unit, so the
protein cannot be made
○
Where is the cell wall found?
In between the capsule and the plasma membrane
Resistance Mechanisms
- Acidification of phagolysosome
- Capsule production
- Toxin release
- Inhibition of phagolysosome formation
- Escape from phagolysome
- Antioxidant production
- Complement inactivation
Prokaryotes
Major groups: Prokaryotes
Size: 0.5 to 3 micrometers
No nucleus
Single, cincular DNA
No mitochondria, no ER, no Golgi
Ribosomes: 70S (50S+30S)
Cytoplasmic membrane: Does not contain sterols
Reproduction: Asexual
Movement: Simple flagellum
Respiration: Via cytoplasmic membrane
Role of Plasmids
Extra chromosomal DNA
Not required for cell survival
Carry genes that code for virulence factors and drug resistance
Transmitted by transformation and mostly by conjugation
Nucleoids
are areas of DNA concentration. Bacterial DNA occurs as a single circular chromosome. E.coli chromosome has 4x106 base pairs, 1mm long ( 1000 times the length of the bacterium, requires gyrase enzyme for coiling)
___________cells are involved in immunosuppression as in EBV infections (mononucleosis, Burkitt’s lymphoma)
T-s cells
Capsule. Gram Positive or Gram Negative
Can be found in both
Iron Overload and Infections
- Excess iron is stored in liver and macrophages as ferritin; regulated by ferroportin and hepcidin
- Iron overload is elevated iron levels in liver; and can cause cardiomyopathy (irregular heart beat), joint pain (arthriris), bone pain, diabetes, liver cirrhosis, hyperpigmentation, hypopituitarism/ low sex drive
- Most important cause is hereditary hemochromatosis
- Another cause is hemosiderosis due to excessive blood transfusion
- Iron overload in people of African descent is due to a mutation in ferroportin gene and can lead to hepatocellular carcinoma
- HIV, Plasmodium falciparum (malaria parasite) require free circulation iron to grow and multiply
- Low circulation non-heme iron in sickle cell disease; low HIV prevalence in people with sickle cell disease
- Iron deficiency (hemoglobin < 10g/dL) protects against severe malaria and death in young children
- Iron supplementation increases severity of HIV and malaria infections
•
Bacterial culture systems
Batch- closed
Chemostat- continous
Growth Measurements
- Cell count- plate/viable
- Cell mass
- Turbidity/ OD
- Cell activity
- Enzyme/ end product
LPS. Gram Positive or Gram Negative
Gram Negative
Role of bacterial classifications
Facilitates proper laboratory identification of clinical isolates
Necessary for determing etiology of infectious diseases during epidemiological investigations
Essential to bacterial nomenclature
○ When the third amino acid is lysine, then we are dealing with ____________
○ When the third amino acid is DAP (Diaminopimelic acid), then it is a _____________
Gram positive bacteria
Gram negative bacteria
Different shapes of bacteria
Spherical cocci
Elongated bacilli
Spiral spirochetes
Corynebacterium diptheriae
Greek korynee, or “club,” referring to its clubbed ends, and diphtheria, meaning “leather hide,”
Exhibits metachromatic granules and “Chinese character”
Pleomorphic gram-positive bacillus
Produces an exotoxin that is encoded by the bacteriophage beta
Diphtheria toxin inhibits protein synthesis
Diphtheria toxin induces pseudomembrane formation
Prevented via vaccination – Diphtheria vaccine
Levaquin
Nucleic Acid inhibitor that inhibits gyrase or topoisomerase, which prevent DNA supercoiling
Treats UTIs and pneumonia
Transduction
- DNA transferred from donor cell to recipient cell via an intact phage.
- Lytic cycle
−Phage replicate and escape via lysis
•lysogenic cycle
−Phage DNA integrates into host genome.
Ex: Corynibacterium diptheriae
*The bacteria itself is harmless, it doesn’t do anything. BUT if you get infected with this bacterium
with a beta 2 phage in it, this causes issues. The bacteriophage encodes for a toxin gene that is
two parts, one part inserts in the membrane the other part is transferred to the inside of the cell
where it interferes with protein synthesis and subsequently kills the cell. The other part that is
stuck to your cell surface has the ability to stick to another cell or it could stick to macrophages
that are coming to degrade it. With these guys sticking together by the toxin part that inserts
into the membrane, you can see how a pseudomembrane would build up.
Capsule
Made of polysaccharides
Antiphagocytic
Role of LPS in clinical symptoms
–LPS binds to CD14 and Toll-like receptor-4 (TLR-4), activates B cells, induces macrophages, dendritic cells to release acute phase proteins IL-1, IL-6, TNF-a and prostaglandings
– LPS activates alternative complement to produce C3a, C5a as chemoattractant, vasodilation, blood capillary leakage and anaphylactoxins
Bacterial sepsis is a life threatening condition due to lipid A from large numbers of circulating G- bacteria.
LPS confers negative charge to bacteria and repels hydrophobic molecules such as antibiotics, bile salts and detergents
Binomial nomenclature
Genus and species
Antiphagocytic Factors
•Polysacch capsule
–Strep. pneumoniae
•M protein
–Group A Strep
- K antigen in E. coli
- Vi antigen Salmonella
- Protein A in S. aureus
Bacterial chromosome
• The chromosome of the bacteria is single chromosome, double stranded DNA
When you look at the bacteria chromosome, if you stretch it, it is about 1000x the length of the
bacteria
•
▪ So, you can give an antibiotic to target the gyrase enzyme
▪ If the bacteria can’t compact the chromosome, it will die
○ They have an enzyme called the gyrase enzyme that allows it to compact all of it
• So how is the bacteria able to compact everything?
This is why we need an understanding of all the part of the bacteria in order to treat the infections
that come along
Catabolite repression also called _____________-
Glucose repression
The presence of glucose inhibits the use of other carbon sources
How can different subspecies of E. Coli be differentiated?
Gel electrophoresis
Teichoic acid. Gram Positive or Gram Negative
Gram Positive
Lactoferrin in Macrophages and Human Milk
- Human macrophages produce lactoferrin as an antimicrobial agent
- Breast milk contains high titers of lactoferrin, lysozyme, lactalbumin
- Our current studies show that they are inhibitory for malaria and bacterial growth and for bacterial hemolysins
- Breastfeeding also protects mothers against future breast cancer
Periplasmic space
Filled with enzymes that regulate what comes in and goes out of bacteria
Only found in gram negative bacteria
Harbor virulence factors
Lysozyme sensitivity. Gram Positive or Gram Negative
Gram Positive: Sensitive
Gram Negative: Resistant
It is that propionic acid that irritates the ___________. Fermentation of what bacteria produces propionic acid?
Subepithelium (can cause pimples)
Propinionic bacterium
_________ and ____________ uses a repressor to switch on and off expression of the operon and uses an attenuator peptide to fine tune expression, while the others rely entirely on the attenuator mechanism for regulation.
Phenylalanine; tryptophan
Resistance to Complement
Damage
- Capsule production
- IgA coating
- Elastase production
- Polysaccharide side chains
- Expulsion of membrane attack complex
More susceptible to antibacterial activity. Gram Positive or Gram Negative
Gram Positive because it does not have the additional outer membrane and periplasm
Vectors of Gene Transfer in Eukaryotic Cells
Bacteriophage
Adenoviruses
Adeno-associated Viruses
Liposomes
Macro-molecular conjugates
- A conjugate with the protein that you want on one end. The other end is recognized by
certain cells. THIS is where you get cell specificity. - Ex. If you wanted to use the insulin receptor to get conjugate material into the cell
- You’d make one end similar to the insulin binding area so that it can bind insulin
receptor- Sometimes they use Ig molecules that will bind their receptors on the cell,
allowing the protein they’re conjugated to, entry to the cell. - This offers cell specificity so you can deliver the protein you need to the right cell
- Sometimes they use Ig molecules that will bind their receptors on the cell,
- You’d make one end similar to the insulin binding area so that it can bind insulin
- Ex. If you wanted to use the insulin receptor to get conjugate material into the cell
Oral Bacterial Flora
- Viridans streptococci
- Anaerobic streptococci
- Bacteroides fragilis
- Fusobacterium sp
- Lactobacillus species
- Candida albicans
How do sRNAs regulate transcription?
—Regulation of translation initiation and transcription termination by altering the accessibility of Ribosome Binding Sites. [Targets]
—Regulation by base pairing with the targeted sequences on mRNAs. [Mechanism]
—Acts in trans
Bacterial floras – regulation and advantages
•Skin bacteria
–Fatty acids
•Intestinal bacteria
–Bacteriocins, colicins
–B & K vitamins
–Antigenic stimulation
–Competent immunity
•Oral & Vaginal floras
–Lactobacillus keeps acid environment & flora intact
Inhibitors of Folic Acid syntheis
PABA
- Sulfonamides
- Sulphadiazine
- sulphamethoxazole
DHFR
- Trimethoprim
- Pyrimethamine
- Methotrexate
Candicen
peptide antibiotic that can kill candida albicans. The gene for this peptide antibiotic was genetically engineered and placed into the acinar cells (that make spit), thereby enabling them to produce spit with this pharmaceutical in it. So every time a patient swallowed a patient was really self-treating. Then if they live long enough, the candida infection can be resolved.
__________ cells and _________ cells are CD4 helper cells
________ and _____________are CD8 cytotoxic and suppressor T cells
__________cells produce IL-2, TNF-α , IL-12 and interferons for macrophage stimulation and intracellular killing and inhibit T-2 cytokine production
________cells produce IL-4, IL-6 and IL-10 cytokines, are good helpers for B cell production of antibodies and inhibit T-I cytokine production
_____________ cells are effective against viruses and virally infected cells
_________ cells are involved in immunosuppression as in EBV infections (mononucleosis, Burkitt’s lymphoma)
T-1; T-2
T-c; T-s
T-1
T-2
T-c
T-s
DNA homology
Compares DNA sequences among bacteria using molecular probes and hybridization studies to determine genetic relatedness
Defenses against entry into the body
The skin is the most important physical barrier against microbial entry into the body due to intact epithelial cover and lactic acid and fatty acids in sweat.
Others include ciliary lining in trachea, HCl in stomach, lysozyme in tears and saliva, lactoferrin and lactoperoxidase in milk.
Antagonistic organisms in oral, nasal, gut and vagina floras
Modes of gene transfer that infect non-dividing cells
Adeno-viruse
Adeno-associated viruses
Liposomes
Macro-molecular conjugates
Conjugation
- Genetic recombination in bacteria that most resembles sexual reproduction.
- Cell to Cell contact.
- Genetic donors (Male)
- genetic recipients (Female)
- fertility factor (Plasmid)
- Pilus + Outer Membrane Protein
- Female becomes Male
(Quorum Sensing)
- Occurs when Males begin to out number females
- This is not beneficial to the cell, so it causes conjugation to stop.
- Females will begin to divide and more females will come in, as a form of regulation
Which proteins must be expressed before lactose is used as a carbon source?
Lac Z: B-galactosidase
- cleaves the linkage between galactose and glucose.
Lac Y: Permease
- Transports lactose into the cell.
Lactose must be transported in
Techoic acids
–They are major surface antigens used for serologic typing.They also play a role in adherence and transport (of magnesium into the cell)
Plasmid Resistance
- Drug Resistance
* Plasmids carry drug resistance genes to
- Penicillin
- Ampicillin
- Beta lactamase
- Tetracyclins
- Kanamycin
- Chloramphenocol
- UV resistance
- UV light causes thymine dimers in bacteria-DNA polymerase cuts out these bumps formed by the thymine dimers, but it can mess up and reinsert thymine dimers. This will alter the reading frame resulting in a non-functional protein. This renders the bacteria non-functional as well. Some bacteria are now resistant to UV light because they have
found a way to repair the damage caused by it.
- Metal Ion resistance to mercury, cobalt, magnesium, silver nitrate
* Silver nitrate drops can act against gonorrhea, so resistance is bad - Bacteriocins
- These are peptide antibiotics that are produced by one bacterium to kill off another species of bacterium. When the host isn’t taking in enough
nutrients, the bacteria turn on each other since there aren’t enough resources for both.
- Production of proteases
- Plasmids carry genes that code fo toxins
- •Exotoxins (Clostridium botulinum)
- Enterotoxins (E. coli, staphylococcus aureus)
- Streptococcal hemolysins, SSST
- Metabolism of various sugars and Hydrocarbons
* Plasmids carry genes that allow for the metabolism of various sugars and hyrdrocarbons - Tumorogenesis
Biofilms
Colonies or communities of bacteria that are enclosed by secreted complex polymers with complex architecture.
The whole colony functions physiologically as a coordinated unit. The polymer enclosures or exopolysaccharide matrix allow cell adhesion and aggregation and make them impermeable and resistant to antibiotics and host immune responses.
Which antibiotics selectively block protein synthesis?
aminoglycosides(streptomycin,tobramycin), and tetracyclines and erythromicin
Oxygen Metabolism
- NADPH oxidase
- Superoxide anion
- Superoxide dismutase
- Hydrogen peroxide
- Ferrous salt
- Hydroyl radical
- Glutathione peroxidase & reductase
- Catalase
Clusters bacteria examples
Staphylococcus aureus
Staph epidermis
Three different ways that bacteria can produce energy
Fermentation- Extension of glycolysis
Glycolysis
Respiration (includes glycolysis, Krebs Cycle, and ETC)
Which bacteria is overgrown in bacterial vaginosis?
- Candida albicans yeast overgrowth (thick white discharge, but no smell)
- Treatable with clotrimazole (lotrimin) gel
Species
Strains with a high degree of overall similarities that differ from other stains
Plasmid
- Extrachromosomal DNA
- DS, circular
- oriC and oriT (terC)
- oriC- start of replication
- oriT- termination of replication
- Independent replication- plasmids don’t depend on the host to replicate
- Variety of types , Carry Optional Genes
- A bacteria can carry many different types of plasmids
•Bacitracin
pervents dephosphorylation of phospholipid carrier, thus blocking regeneration of carrier molecule
In between the peptidoglycan and the outer membrane you have the ____________-
Periplasmic space
Iron Metabolism in Bacteria
- Bacterial iron-containing enzymes(cytochromes, catalase)
- Bacterioferritin—bacterial iron storage
- Host iron-containing proteins (hemoglobin, ferritin)
- Host iron-transport proteins (transferrin, lactoferrin)
- Bacterial iron-sequestration
- siderophores- ferrichromes,enterobactins
- membrane-receptor proteins
- host cell iron exporters (ferroportin, hepcidin)
- Iron overload in malaria, sickle cell disease (blood transfusions)
- Iron chelators (desferrioxamine)-infections
Plasmid Types
•F Plasmid
- Conjugative Plasmid
•F’ Plasmid
- Integrates with host chromosome and can come back out
- HFR Plasmid
- High Frequency of recombination
•Drug Resistance Plasmid
Transfection
•Insertion of “naked bacteriophage” DNA to produce infectious phage particles.
•
•“Man-made” or laboratory mechanism
•Host genetic defects in colon mucosal barrier function, innate bacterial killing or immunoregulation may alter anaerobic microbial composition and result in continuous inflammation by exotoxins of _____________ and development of ______________ and ____________
Clostridium difficile; Crohn’s disease; ulcerative colitis
Regulator of normal vaginal flora
Lactobacillus
_______________ allow the bacterium to adhere to host epithelial cells.
Pili (fimbriae)
Where does ETC occur in bacteria?
In the cytoplasm
Plasmid
Small amount of DNA
a genetic structure in a cell that can replicate independently of the chromosomes, typically a small circular DNA strand in the cytoplasm of a bacterium or protozoan
Carry genes that encode for resistance to antibiotics
Carries genes for toxic production
No necessary for the survival of a bacteria
Diplococci bacteria examples
Gram Positive
Streptococcus pnemoniae
Gram Negative
Neisseria gonorrhea
N. sicca
N. meningitidis
•Glycopeptides (vancomycin)
- bind to terminal D-ala-D-ala residues, thus preventing incorporation of subunit into growing peptidoglycan
As Viruses and intracellular bacteria multiply, they ____________________, _______________and _________________.
kill cells with toxin production and inflammation; induce chronic infections ; evade host humoral immune responses
Fermentation product of yeast cells
Ethanol and carbon dioxide
Class 1 Integron
A genetic element that possesses a site, at which additional DNA, in the form of gene cassettes, can be integrated by site-specific recombination, and which encodes an enzyme, integrase, that mediates these site-specific recombination events. So, it’s a genetic unit that includes genes for a site specific recombination, they can capture and mobilize genes contained in mobile elements.
○ When integrons acquire antibiotic genes they make a cassette out of it. Gene cassette is a type of mobile genetic element that contains a gene and a recombination site. Gene cassettes can move around within an organism genome or be transferred to another organism in the environment via horizontal gene transfer. These cassettes often carry antibiotic resistance gene
SINGLE PROMOTOR. All genes on or all genes off
Two types of respiration
▪ For aerobic respiration, all 3 things: glycolysis, Krebs, & ETS have to be present
▪ An oxygen molecule is the final electron acceptor in ETS
○ Aerobic
○ Anaerobic
Components of Trp Operon
○ A promoter
○ An operator
○ A repressor gene
Structural enzymes, which are involved in the biosynthesis of tryptophan
Mode of action for enzymatic lysis
This toxin behaves like a phospholipase c by degrading the phospholipid content of the cell
membrane, thus allowing it to lyse the cell membrane
○
○ Once the cells are lysed, the bacteria can’t survive and cell death results
Modes of gene transfer that are now in clinical use
Retro-viruses
Adeno-viruses
Liposomes
Causes of UTIs
•
–Tumors
– Kidney stones
– Ureteric reflux
– Prostatic hypertrophy
–Bladder incontinence
– Short female urethra
– Catherization
–Poor hygiene/ GI Urethral Contamination (by E. Coli and Klebsiella)
Modes of gene transfer that effects stable gene integration
Retroviruses
Adeno-associated viruses
How does rifampin work?
Inhibits RNA synthesis by binding to DNA- dependent RNA polymerase
Two types of professional phagocytes
(a) is a blood monocyte ,long-lived with mitochondria, antigen presenting, produces IL-1, TNF-α, IL-6
(b) is a polymorphonuclear neutrophil, short-lived without mitochondria, uses glycolysis under anaerobic conditions such as in inflammatory focus, nonantigen presenting or cytokine production
Diptheria Toxin Regulation
The dtxR bacterial gene encodes a 226 AA DtxR repressor protein
The DtxR repressor is inactive by itself
Fe+2 is a co-repressor* of DtxR
The DtxR-Fe+2 complex is a DNA binding protein that binds to the bacteriophage tox operator to inhibit transcription
• Repressor also binds to siderophore transport genes
- ○ Siderophores are iron sequestration
Acid fast bacteria
Mycobacterium species, neither gram positive nor negative);cell wall with peptidoglycan and layers of cord factor and mycolic acid
Modes of gene transfer that accomodates genes of reasonable size
Retro-viruses
Adeno-viruses
Aden-associated viruses
Liposomes
Macro-molecular conjugates
Genus
Collection of similiar species
The F sex pilus is used for ___________ and __________
bacterial conjugation and DNA transfer.
Signficance of lactobacillus
Lactobacillus is an important member of the vaginal flora because it regulates that flora through the production of lactic acid because it provides an acidic environment that keeps every member of that flora in check
□
The overuse of antibiotics can decimate Lactobacillus, wipe out the flora, and dysregulate the dynamics of the population
There are some people who have a hormonal defect that affects regulation of the flora
In the mouth and oral cavities, Lactobacillus plays a role in the formation of dental carries
If you wipe out Lactobacillus from that flora, there’s no regulation, so everyone
will go wild and you have bacterial vaginosis
□
Plasmids
Plasmids are extrachromosomal DNA found in all genera of bacteria. Plasmids are of medical importance because they carry genes for resistance to antibiotics, toxin production and virulence factors
Many bacteria multiply outside host cells on mucosal cells and in blood circulation ,e.g ______, _______, ___________, and ____________.
E.coli, Staphylococci, Streptococci, Pseudomonas
Antibiotics that inhibit antimetabolites
Sulfonamides
Dapsone
Trimethoprim
Para-aminosalicyclic acid
In product of fermentation for many bacteria found in our GI tract?
Mixture of organic acids
BACTERIAL ENDOSPORES
How? What? When?
Spore formation is characteristic of two genera,Bacillus (aerobes) and Clostridium ( anaerobes)
Sporulation occurs when the bacterium is under environmental stress e.g. lack of nutrients, extreme temperatures or conditions unfavorable to growth
The structure and chemistry of the bacterial spore allows it to resist physical and chemical conditions that are detrimental to the vegetative form of the bacterium
Bacterial spores are of medical significance they are means of dissemination of certain diseases
Bacterial spores are destroyed by autoclaving
Streptococci bacteria examples
S.pyrogenes
S.mutans
Which bacteria produce a lot of capsule?
Proteus
Klebsiella
When will the CAP protein bind to the CAP site?
When cAMP levels are high
The catabolic activating protein will not bind to the site by itself. It will
only bind when in complex with cyclic AMP
Oxygen utilization. Which bacteria?
Obligate aerobes- bacillus
Faculative anaerobes- E. Coli, Staph
Aerotolerant anaerobes- Lactobacillus
Microaerophiles (need oxygen but poisioned by high concentrations)- Campylobacteria
Obligate anaerobes- Clostridium
Spore formation is characteristic of two genera,____________ and ______________
Bacillus (aerobes); Clostridium ( anaerobes)
Siderophores
a molecule that binds and transports iron in microorganisms.
•Cycloserin
inhibits reactions involved in incorporation of alanine into cell wall precursor
–S. aureus protein A binds Fc portion of______
IgG
Phylogenetic relatedness is determined by comparisons of ______ sequences among bacteria.
16srRNA
Macromolecules in Bacteria
•Protein: 2,360,000/cell
– ( 1,050 types)
–DNA: (1 type)
–23S,16S,5S rRNAs,1type
–tRNA 60 types
–mRNA 400 types
–Lipid: 22,000,000/cell
(4 types)
–LPS: 1,200,000/cell
–Peptidoglycan:1/cell
–Glycogen 4,360/cell
Modes of gene transfer that have cell-type specificity
Macromolecular conjugates
Regulons
Regulons allow the co-ordinate up-regulation of multiple genes/operons
in response to a common environmental signal / regulatory molecule
The SOS response is one such regulon.
SOS response is activated by DNA damage and it coordinates various functions required to control DNA damage.
At least 15 genes at different chromosomal locations are controlled by the action of a repressor protein-LexA.
In the absence of DNA damage, LexA represses SOS induced genes by binding to their operator regions.
Following DNA damage, a second regulatory protein, RecA binds to ssDNA and RecA proteolytically cleaves the LexA repressor.
Proteolysis of LexA activates expression of genes in the SOS regulon.
LPS contains lipid A, an important endotoxin responsible for the life-threating condition of___________. Lipid A is a potent activator of _________
bacterial sepsis; TLR-4.
TLR-4’s activation leads to an intracellular signaling pathway NF-κB and inflammatory cytokine production which is responsible for activating the innate immune system
How does translational control occur?
By changing the shape of the mRNA
Host response to strep pnemonia
Release of neutrophils that can phagocytose
Enzymes found in periplasmic space
–phosphatases ,proteases, endonucleases
Mode of action for hyperactivation
will bind to the surface of the target cell’s membrane
○ They will inject subunits of the toxin
○ The subunits of the toxin will activate cyclic AMP
The cyclic AMP will turn around and push all the electrolytes out of our system (fluid will
also be pushed out)
○
○ Organisms like E.coli that cause diarrhea. Diphtheria.
Antimembrane agents
Polymyxins
- Anti-bacterial; disrupts hydrophobic region of cell membrane; possess multiple positive charges to bind phospholipid phosphatases
Polyenes
- Anti-fungal; react with steroids in cell membrane to alter permeability
The TrpL sequence
- Leader peptide
- Contains 2 UGG Trp codons inside
- this mRNA transcript that makes secondary structures
- There are several RNA secondary structures you can make
- ○ You can make a 2-3 stem loop (low tryptophan)
○ You can make a 3-4 stem loop (High tryptophan)- transciptional terminator, if it is followed by a poly U.
- Poly U activates RNA polymerase
○ OR, you can make both
- ○ You can make a 2-3 stem loop (low tryptophan)
- There are several RNA secondary structures you can make
Which type of bacteria has a thicker cell wall?
Gram positive
What differentiates the cell membrane of prokaryotes from eukaryotes?
The lack of sterols
Trp Operon
- Absence of tryptophan activates expression of genes required to synthesize tryptophan.
- Regulation aims to switch off expression when tryptophan is plentiful.
This is the opposite of lac control
One level of control operates through TrpR the trp repressor. Tryptophan acts as a co-repressor with TrpR.
Trp operon encodes enzymes of the shikimate pathway that convert Chorismate to tryptophan
Eukaryotes that pathogenic to us
Plasmodium species (malaria)
Trichomonas vaginalis (STD)
Toxoplasma gondii
Candida albicans (oral, vaginal candidaiasis)
Examples of diseases that different to treat due to the prescence of biofilms
Cystic fibrosis
UTIs
•Proportions of ________________ and some anaerobes in mouths of patients with oral cancer are >2X that of healthy controls
Streptococcus mitis
Peptidoglycan cross link in gram positive bacteria
Pentapeptide
*No link in gram negative
Where are antiphagocytic factors found? Which compounds are considered antiphagocytic?
Many in the capsule
M protein, which is found in the cell wall but functions in the capsule
Components of periplasmic space
Enzymes involved in transport, degradation, and synthesis
–binding proteins for sugars, amino acids, inorganic ions, vitamins
–chemoreceptors that influence motility
–Drug resistance enzymes such as beta- lactamase
TRANSPOSONS
- Closely related to IS elements.
- Carry a variety of genes, especially antibiotic resistance genes.
- Three Types
- A. Auxiliary genes flanked by IS elements
- ex. Cmr transposon Tn9
- B. No IS flanking elements. Contains 2 genes, Transposase and Resolvase.
- Ex. Beta lactamase Tn3
- C. Conjugative Transposons in Streptococcus
•
Transformation
- Uptake of “naked” (NO PROTEINS) , fragmented bacterial DNA.
- Competency of bacterial cells (bacterial cells have to be competent to take up the DNA)
- Mechanism
- absorption
- •entry
- •incorporation
- •G+ cells get ss DNA
- •G- cells get dsDNA but integrate only 1 strand
Which species form capsules?
Haemophilus, Neisseria, Klebseilla, Streptococcus, E.coli and Bacillus
Exotoxin. Gram Positive or Gram Negative
Can be found in both
Diptheria toxin
• Diphtheria toxin inhibits protein synthesis
• It’s an a and b toxin
It’s activity is an ADPR & it’s substrate is EF-2, when they are together, it’s inactive so protein synthesis is inhibited
▪
○ A stands for activity
• The b portion binds to the receptor and the a portion is taken in
Causes of Bacterial Vaginosis
- Loss of regulation
- Overgrowth of gram negative bacteria
- Flora disruption
- Physiological imbalance
- Gardrenella vaginalis
- Bacteroides species,
- Mobiluncus species
- Occurs when the normal balance of bacteria in the vagina is disrupted and replaced by an overgrowth of certain bacteria.
- Common in pregnant women and women of child-bearing age
- accompanied by white or gray discharge, fishy-smelling odor, pain, itching, or burning urination.
- Increased risks include douching; new or multiple sexual partners
•
Mode of action for Inhibition of Nerve-Muscle transmission
You also have bacteria that have neurotoxins, which prevent the transmission of the
electrical signals that cause either muscle contraction or muscle relaxation
Colon Flora
- Bacteroides fragilis
- Fusobacterium nucleatum
- E. coli
- Clostridium difficile
- Lactobacillus acidophilus and other species
What factors to bacteria use to become invasive?
They use a lot of enzymes. especially hydrolytic enzymes
Mucus on plate in indicative of
Capsule
Bacterial additional morphology
Single bacillus
- E. coli (diarrhea, septicemia, UTI), Pseudomonas aeruginosa (in cystic fibrosis, burn trauma); Lactobacillus species; Clostridium perfringes (myonecrosis, gangrene)
Coccobacillus
- Bordetella pertussis (whooping cough)
- Hemophilus influenzae (childhood meningitis)
Vibrio (curved)
- Vibrio cholera (profuse diarrhea)
Spirillum (spiral)
- Borellia burgdorferi (Lyme disease)
Spirochete (cork screw)
- Treponema pallidum (syphilis)
Branched Filamentous (Nocardia, Actinomyces)
Model Regulatory Systems
The Operon, Transcriptional Control
- lac, trp
Catabolite Repression: lac
Attenuation, Post-Transcriptional Control
- trpL
Translational Control
Regulons
- SOS System
- Sigma Factors
- DtxR
Three lines of immune responses and protection
Natural barriers/exterior defenses
Innate antigen-nonspecific defenses
-rapid, local responses (fever, complement,
inflammation, phagocytosis, cytokines)
Acquired (adaptive) antigen-specific responses
-specifically target microbial pathogens that
pass through first two defenses (antibodies, B and T cells)
The most common organism that causes UTIs?
E. coli, followed by Klepsiella
Elevated neutrophils =______________
○ Elevated eosinophils = ________________
Elevated lymphocytes =_______________
Elevated basophls=________________
bacterial infection
parasitic infection or allergy
intracellular infection like viral or fungal infection
allergic reaction
Fermentation
A metabolic process that consumes sugar in the absence of oxygen. The products are organic acids, gases, or alcohol. It occurs in yeast andbacteria, and also in oxygen-starved muscle cells
Lipid A causes:
–cells to produce abnormal amounts of cellular products (cytokines) that normally regulate vascular permeability, blood pressure, blood coagulation and immune responses
How do beta lactam antibiotics inhibit cell wall formation in bacteria?
By inhibiting cross linkaages of peptidoglycan units
____________ and __________ are required for heat resistance in spores.
Calcium; dipicolinic acid
3 components of Insertional elements
direct repeat (both sides), inverted repeat (both sides) , and the core area encoding for transposase genes which will move the gene
Exotoxins
•Enzymatic lysis
alpha toxin—Clostridium perfringes
• Pore formation
alpha hemolysin — Staph aureus
•Protein synthesis inhibition (80s ribosome)
diphtheria & shigella toxins
•Nerve-muscle transmission-inhibition
tetanus toxin-spastic paralysis
botulinum toxin-flaccid paralysis
Antibiotics that inhibit DNA replication
Quinolenes
Metronidazole
Clofazimine
Insertional Elements
- Can insert into new sites on the same or a different chromosome (replicon).
- Can NOT replicate autonomously.
- Contains a single gene that codes for Transposase.
- Most have a similar structure (~1,000bp)
- Deletions, duplications, translocations and fusions.
- Requires little specificity for the DNA sequence in which it inserts.
Insertion sequences (IS’s) are transposable elements whose only genes
are directly related to promotion and regulation of their transposition,
- Ends contain inverted repeats of 10-50bp.
- Mycobacterium tuberculosis IS 16100.
Functions of the cell membrane
–Osmotic barrier (fig. 3-8)
–Electron transport and energy production
–Ion pumps for membrane potential
–Anchor for cell wall biosynthesis
–Chemotaxis and flagella activity
–Transport of molecules (proteins)
–Actin-like protein filaments for bacterial shape
–Site of septum formation
Intracellular killing of engulfed bacteria
- Lysosomal enzyme degradation
- Oxidative / Respiratory Burst
Hydrolytic Enzymes
- Lysozyme
- Lactoferrin
- Collagenase
- Acid phosphatase
- Cationic proteins
Medically important bacteria are classified according to ____________, _____________, and _____________ characteristics.
Phenotypic, analytic, and genotypic
In product of fermentation of mouth bacteria?
Lactic Acid
Significance:In the mouth and oral cavities, Lactobacillus plays a role in the formation
of dental carries
How is the cell wall of bacteria unique?
It is many up of aminosugars
Aminosugars have been exploited to create antibiotics that can tag and destroy it
Role of LPS in septic shock
-IL-1, once produced will get into circulation and travel to the hypothalamus where it will
upregulate the thermal center to increase the body’s temperature, thereby causing a fever.
The extent of the fever will be directly proportional to the amount of LPS in circulation that is
stimulating the macrophages. A low level will lead to a slight discomfort, a higher amount will lead
to a higher fever.
-
TNF-alpha can also go to the liver and induce the liver to release less sugar into circulation in order to deprive the pathogens of needed nutrients for their metabolism and proliferation
○
It also downregulates the release of iron into circulation. ALL organisms require iron for
their multiplication/metabolism. This is done in an effort to impede bacterial multiplication
○
TNF-alpha does lot more. It will go to the endothelial cells and increase the production of
adhesion molecules on the endothelial cells (ICAM-1 and VCAM-1). The upregulation of these two
adhesion molecules will increase permeability of the vasculature and will allow fluid to leak out of
blood circulation. Leakage will lead to a drop in BP (hypotension)
-
Alternative complement pathway activation: leading to production of C3a and C5a which will also
increase vascular permeability and contribute to onset of hypotension.
-
Clotting cascade: LPS can also induce the clotting pathway, which leads to intravascular
coagulation. Blood clots in circulation will prevent essential organs from receiving nutrients and
oxygen from the blood-a lack of these two will cause ultimate failure (multiple organ failure will
then lead to septic shock. If not reversed, you will die from it.
-
IgE- LPS can also induce production of IgE which will bind to mast cells and cause their
degranulation leading to release of histamine and serotonin. These two will also contribute to the
increasing of vascular permeability.
A lot of the endoenzymes are used for ______________, but a lot of the extracellular enzymes
are used for ______________
metabolic activity; pathogenicity
Attenuation
- The premature termination of transcripts
- Itself allows for a 600 fold range in expression of tryptophan genes
- All due to the TrpL region
- Within the gene for TrpL is an attenuator sequence called the attenuator site
- This is a second regulatory region, which allows attenuation to occur
Certain bacterial species multiply inside host cells (phagocytes), for example, ____________,________,_________, and _____________. All ______________are obligate intracellular parasites
Shigella Mycobacteria, Salmonella, Neisseria, Chlamydia
viruses
Oxygen-deprived, nerve-damaged skin as in chronic diabetes breeds _____________from invasive infections by skin flora and can lead to_____________
diabetic ulcers ; amputation
Regulation sites in glycolysis
ATP, ADP
PEP
PFK
Antibiotics that inhibit RNA synthesis
Rifampin
Rifabutin
lacI
- The lac repressor is a sequence-specific DNA-binding protein that Negatively regulates the expression of the lac operon structural genes.
- trans-acting element
- Inactivated by lactose
- When an inducer such as lactose or allolactose is present, it binds to the repressor. In this form it cannot bind to the DNA operator sequence and RNA polymerase is free to bind and activate transcription of the lac operon.
Two types of intracellular killing
Oxygen-dependent- When a phagocyte ingests bacteria (or any material), its oxygen consumption increases. The increase in oxygen consumption, called a respiratory burst, produces reactive oxygen-containing molecules that are anti-microbial. The oxygen compounds are toxic to both the invader and the cell itself, so they are kept in compartments inside the cell.
- Type I
- oxygen-dependent production of a superoxide, which is an oxygen-rich bacteria-killing substance. The superoxide is converted to hydrogen peroxide and singlet oxygen by an enzyme called superoxide dismutase. Superoxides also react with the hydrogen peroxide to produce hydroxyl radicals, which assist in killing the invading microbe
- Type II
- involves the use of the enzyme myeloperoxidase from neutrophil granules. When granules fuse with a phagosome, myeloperoxidase is released into the phagolysosome, and this enzyme uses hydrogen peroxide and chlorine to create hypochlorite, a substance used in domestic bleach. Hypochlorite is extremely toxic to bacteria.
Oxygen- independent
- not as effective as the oxygen-dependent ones.
- There are four main types. The first uses electrically charged proteins that damage the bacterium’s membrane. The second type uses lysozymes; these enzymes break down the bacterial cell wall. The third type uses lactoferrins, which are present in neutrophil granules and remove essential iron from bacteria.The fourth type uses proteases and hydrolytic enzymes; these enzymes are used to digest the proteins of destroyed bacteria.
lac operon is composed of…
3 genes lacZ , lacY and lacA, a promoter, operator and terminator.
All are co-transcribed to make a single mRNA.
Each gene is independently translated into protein from the same mRNA.
This is called a poly-cistronic or polygenic mRNA.
Gene expression is controlled transcriptionally by an adjacent gene called lacI.
lacI has its own promoter and terminator so is not part of the lac operon.
Most bacterial capsules consist of polysaccharides, except______________ with polypeptide capsule
Bacillus anthracis
Endotoxin. Gram Positive or Gram Negative
Gram Negative
Examples of extracellular enzymes that allow for invasiveness of bacteria
• Extracellular enzymes
–Hyaluronidase dissolves connective tissue
–Collagenase hydrolyses muscle connective tissue
–Streptokinase lyses blood clots
–Phospholipases damage cell membranes
–Lecithinase damages cell membranes
–Staphylokinase (fibrinolysin) dissolves fibrin clots
_ Hemolysins lyse erythrocytes and white blood cells
Composite transposons components
generally consist of two copies of the same IS element flanking variable amounts of other DNA sequences coding for one or several genes with diverse functions. The best known transposons are those which were discovered as parts of antibiotic resistance plasmids
Peptidoglycan
Glycan chains of GlcNac and MurNac cross-linked by peptide bridges
Thicker in gram positive bacteria
Mode of action for pore formation
Bacteria that contain exotoxins that work through pore formation will punch a hole in the
membrane, which causes cell death
Different arrangements
Pairs (Dipplococci)
Chains (Streptococci)
Clusters (Staplococci)
Which toll-like receptors do gram positive and gram negative bacteria activate respectively?
TLR-2 AND TLR-4
