Intro to Bacteriology Flashcards
Where does protein synthesis occur in eukaryotes?
80s ribosomes
Describe the nucleoid structure of prokaryotes.
mass of genetic material with no membrane or envelope has supercoiled DNA and condensed with scaffold proteins
What is unique about transcription and translation of mRNA in bacteria?
they could occur simultaneously
How does gram staining with crystal violet works?
stains cytoplasmic elements
List the steps of gram staining.
1) crystal violet 2) gram’s iodine 3) decolorizer (alcohol/acetone) 4) safranin red
What’s the function of the gram’s iodine?
complexes with crystal violet and acts as mordant (chemical that fixes the dye)
What does the decolorizer does to the gram + bacteria?
(THICK peptidoglycan) - dye-iodine complex will NOT wash out - organism stays purple
What does the decolorizer does to the gram - bacteria?
(THIN peptidoglycan) - only crystal violent is washed out - become unstained
What’s the point of the safranin red stain?
a counterstain no effect on the gram + bacteria (already purple) makes the gram - bacteria pink bc it’s now unstained
What can antibiotics do to the shape/size of bacteria?
can change the original shape/size -> make cocci bacteria appear as rods
What stain can be used to penetrate the cell wall of bacteria (where gram staining doesn’t work)?
acid fast stain
What are the steps of acid fast stains?
1) stain with carbolfuchsin red
2) add decolorizer
3) add methylene blue
What does the decolorizer do to acid fast positive bacteria?
bacteria remains red - stain will not wash out
What does the decolorizer do to acid fast negative bacteria?
become colorless
Which bacteria will be stained blue with methylene blue counterstain?
non-acid fast bacteria
What determines if a bacteria will have a capsule or not?
growth conditions (microenvironment) bc capsules take a lot of energy to produce
How does a capsule protect against innate defense mechanisms?
1) complement binds capsule and forms MAC
2) make is ineffective against capsule because pore does not penetrate deep enough to reach cytoplasm
How do capsules prevent phagocytosis?
makes the bacteria very “sticky” so phagocytic cells have hard time adhering
What are capsules made of?
high MW polysaccharide or peptide
What are the components of the gram positive envelope?
1) THICK peptidoglycan layer on outside of PM
2) teichoic and lipoteichoic acids intewovened in the peptidoglycan - helps give strength and stability (lipo anchors peptidoglycan to PM)
3) periplasmic space
4) various transmembrane proteins in plasma membrane
What occurs in the periplasmic space?
located in between the outer peptidoglycan layer and PM - where synthesis of peptidoglycan occurs
(more impt and larger in gram - bacteria)
What makes up peptidoglycan?
N-acetylglucosamine crosslinked by peptidoglycan interbridges to N-acetylmuramic acid
the different layers are connected by peptide chains forming an infrastructure that resembles chain-linked fence
What’s the function of peptidoglycan?
unique to bacteria (great target for antibiotics)
give bacteria strength, integrity and shape - acts as cytoskeleton
What makes up the gram (-) cell envelope?
THIN peptidoglycan layer within periplasmic space
Outermost layer is outer phospholipid membrane with lipopolysaccharides embedded (some drugs that work on gram (+) will not work on gram negative simply bc it posses this outer phospholipid membrane)
inner plasma membrane contains its own set of proteins
porins transversing the outer membrane
What’s the function of the proteins on the inner plasma membrane?
used for intracellular processes such as respiration and oxidative phosphorylation (since it does not have mitochondria)
What’s significant about the periplasmic space for gram (-) bacteria?
contains enzymes that destroy antibiotics before they penetrate the inner plasma membrane and reach the cytosol
What’s another name for lipopolysaccharide (LPS)?
lipoglycan and endotoxin
What’s the importance of LPS?
binds the CD14 receptor in immune cells and initiates secretion of cytokines
What’s the importance of Lipid A?
the endotoxin of LPS - illicits the immune response/cytokine release via binding to CD14
(hydrophobic segment that sits in the membrane)
What’s the role of porins?
gatekeepers of the cell - can actively pump antibiotics
What are exotoxins?
damaging toxins that are secreted by bacteria
What are the O side chains of LPS?
the carbohydrates that the body sees and makes Ab against
used in bacterial serotyping
can bind to Mg or Ca to add some structural integrity to the cell and prevent some antibiotics from working
Where are many of the proteins and enzymes needed for bacteria metabolism?
embedded within the cell membrane
List some examples of proteins on the cell membrane.
- transporters
- anabolic enzymes
- enzymes that generate ATP (cytochrome oxidase system)
- cell motility (flagella and pili)
- mediation of chromosomal segregation
- molecular sensors (drive bacterial movement towards/away favorable/hostile environments)
What are pili composed of?
pilin
What’s the function of common pili?
(fimbrae or type IV)
mediates attachment of bacterial cell to host cells or any surface
it also inhibits phagocytosis!
The pili are antigenic
What’s the function of sex pili?
used for exchange of genetic material, conjugation
What are inclusion bodies?
storage granules where bacteria hoard excess nutrients and minerals
may look like clearing inside the cell
What are nucleoids?
highly coiled bacterial chromosomes intermixed with RNA, polyamines, and support (scaffold) proteins - DO NOT have outer membrane
some drugs can inhibit supercoiling making the genome very lose and disorganized
What is kept safe within a spore?
genetic material!
What makes up flagella?
rotary motor, hook, and propeller (flagellin - highly antigenic)
What happens when you turn off the gears of the flagella?
tumbles in place until the gears are turned back on to propel it somewhere
How do bacteria bring in the nutrients they need?
simple diffusion, facilitated diffusion, active transport
Why is it bad to have free iron floating around in our body?
bacteria can uptake the iron through active transport and use it as a source of fuel!
How do bacteria use sideophores?
a strong iron-binding agent that will strip the iron from our body’s cells to be used for bacterial functions
What are the 3 main pathways where percursor metabolites are produced and consumed?
- Emden-Myerhof-Parnas (EMP) Pathway (aka glycolytic or anaerobic pathway)
- Tricarboxylica acid cycle (TCA)
- Pentose phosphate pathway
What are fastidious organisms?
pathogens that can no longer make a nutrient required for life and depends on human metabolism to make that nutrient
What determines the production efficiencies of bacteria’s precursor metabolites?
growth conditions and nutrient availability
What pathways produce high energy phosphate bonds?
TCA and EMP pathways (ADP->ATP)
What is the initial substrate of substrate level phosphorylation?
pyruvate (O2 is not required!)
What are the end products of substrate level phosphorylation?
organic acids, alcohols, CO2 and hydrogen
(the different end products can be used to ID the bacteria!)
What type of metabolism does pyruvate undergo for us to get the endproducts?
fermentative metabolism
How are enterotubes used to ID bacteria?
1) innoculate the compartments with different colonies of bacteria and test for one of the metabolic end products
2) compare the product to a color chart to ID
How is selective media used?
used for growing a single or handful of species from a specimen of thousands of species (allows the growth of some bacteria while inhibitting the growth of others)
How is differential media used?
used for differentiating closely related organisms or groups of organisms by using certain dyes or chemicals to produce characteristic growth patterns
What could be used to ID bacteria that cannot be grown in culture?
sequencing 16S ribosomal RNA (molecular fingerprint)
What pathway is shared by us and bacteria?
oxidative phosphorylation! (both anaerobic and aerobic forms)
so cannot manipulate this pathway in antibiotics bc it will be toxic to us as well
What enzymes do aerobics have to detoxify molecular oxygen?
catalase and superoxide dismutase
What is a facultative aerobe?
can use O2 if present, but can also survive on anaerobic metabolism
What’s microaerophilic?
not true anaerobe - grows best at low O2
What was the first antibiotic?
protonsil
Explain the magic bullet theory.
there were chemicals that you could put in the body that would only target microorganisms causing disease and not the host
How does protonsil work?
sulfa drug (a pro-drug) that blocks the synthesis of folic acid (bacteria have to synthesize their own folic acids while human hosts obtain theirs from diet)
What’s trimethoprim?
another drug that interferes with folate metabolism by inhibiting bacterial dihydrofolate reductase (DHFR)
How do bacteria get the proteins generated inside the cytoplasm to the outside of the cell?
they have docking ports for chaperone proteins embedded in the membrane that direct proteins to exporters outside of the bacteria and into environment
What’s the significance of protein secretion in gram (-) bacteria?
must secrete past 2 cell membranes (secretion channels types I-IV)
What’s important about the type III secretion system?
used for virulence
“needle and syringe” for inserting proteins into eukaryotic cells
What are the key enzymes used to unwind tightly coiled DNA?
DNA gyrase and topoisomerase
How do chromosomes stick to cytoplasmic membrane at specific sites during replication?
since no mitotic spindles, make use of mesosomes
Define F plasmids.
chromosomal exchange between bacteria (essential for replicating plasmid and transferring from one to another)
F= fertility; encodes the info for making sex pili (made by males)
Define R plasmids.
R= resistance
carry genes encoding antibiotic resistance
Define Virulence plasmids.
carry genes encoding toxis or other virulence factors
What’s the genome of a bacteriophage?
RNA or DNA
What’s significant about the virulence factors of bacteriophages?
can encode virulence factors that bacteria can use - staph enterotoxins or diptheria toxin
some pathogens actually need to be infected with the phage to become virulent
What is transduction?
with the use of bacteriophages, allows the exchanging of DNA info between different bacteria
consist of a lytic and lysogenic cycle
Define the lytic cycle.
Phage gets into the cell using the cells machinery. Phage leaves the cell by lysing
Define the lysogenic cycle.
- Some of the phage DNA gets incorporated in the host genome.
- In order to replicate, the phage DNA has to pop out of the bacterial chromosome - this process causes some of the phage DNA to be swapped with some of the bacterial DNA when - forming hybrid phage
How does transduction occur?
when the hybrid phage (phage DNA + bacterial DNA) move to infect a new bacterial host after lysis, it transfers DNA between bacteria
What are restriction enzymes?
function like “bacterial immune system” against phage DNA (chops up the foreign DNA) - destroys whatever can potentially kill the bacteria
What makes transformation different from transduction?
bacteria takes up free floating DNA fragments (no need for phages!)
Where do the free floating fragments of DNA come from?
bacteria that die release their DNA into environment to either be degraded or transformed into other bacteria
What happens during conjugation?
two microbes physically meet and one extends its sex pili to another recipient cell allowing for tranfer of genetic material
What are transposons?
jumping genes - piece of genetic material that pops out and either re-inserts on same chromosome or another chromosome during transposition
can be transferred in plasmids during the process of conjugation
What are pathogenicity islands?
compressed pieces of genome with all the virulence factors in one location - EVERYTHING the bacteria need to be pathogenic is in one place
How do pathogenicity islands make a nonvirulent bacteria virulent?
the islands can mobilize and transfer all the virulent factors (toxins and proteins) from one organism to another by conjugation, transformation, or transduction
What does a perfect life cycle of bacteria look like?
lag phase: bacteria gathering up enzymes
log phase: metabolic peak; replication occurs exponentially
stationary phase: rate of growth = rate of death; runs out of gas
death phase: bacterial decline due to exhaust of nutrients and accumulation of wastes
What apparatus is used to grow bacteria?
chemostat - keeps bacteria in log phase
Explain bacteria metabolic parsimony.
bacteria expend energy only if they have to - way for bacteria to adapt
Define sterilization.
kills ALL microbial forms - including spores
done so with autoclaving and dry heat
How does autoclaving work?
121OC, 15 psi, 20 min
kills by denaturation of proteins and nucleic acids - disrupts membranes - utilizing steam under pressure to kill
How does dry heat work?
2 hr at 160OC
kills same as steam
What are two other methods of sterilization?
1) UV or ionizing radiation (gamma rays): damages nucleic acids; used on US mails and tissues for transplant
2) gas vapors (chemical autoclaves): ethylene oxide or formaldehyde vapors; work by alkylating agents - used on anything that can withstand heat
What’s disinfection?
most microbial forms are destroyed; spores and other resistant forms endure
it only reduces the microbial burden on the surface
environmental conditions affect effectiveness - soil and dirt blocks the effectiveness of the bleach (chloride compounds - oxidize sulfhydryl groups) and lysol (phenolic compounds- denature proteins) (does not do well with living cells)
What should be used on living cells?
antispesis
Define antisepsis.
microbes are inhibitted or eliminated in or on living tissue
no sporocidal activity implied
ethyl or isopropyl alchols denature proteins
iodophors (providone iodine) also denature proteins - betadine
