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
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.
