Bacterial Nutrition/Metabolism Flashcards
Mycobacterium leprae: what does it cause, where does it have to grow to be studied?
Leprosy
Grown in mice and nine-banded armadillo
Treponema pallidum: what does it cause, where does it have to be grown to study?
Syphilis
Needs to be grown in rabbit testes (loses infectivity if grown in primary cell culture)
Can bacteria rapidly adjust from rich to poor nutrients? Is lag time experienced after transitions?
Yes they can adjust
Very brief lag times
E. coli example for nutrient transition/doubling time change?
Doubles in 60 minutes in minimal media
Doubles in 20 minutes in rich media
What is an enrichment culture?
Liquid medium that favors the growth of desired organism
For an enrichment culture, the conditions are usually minimal for the organism. Example?
Azotobacter - leave out nonvolatile nitrates so that it has to fix nitrogen
What is selective medium?
Solid medium (agar) that specifically selects one type of organism and inhibits the growth of others Takes advantage of specific metabolic requirements/set of conditions
What is a differential medium?
Solid medium (agar) plates on which the organism of interest has a distinctive appearance. It is not necessarily selective, which means that other organisms can grow.
Blood agar: selective, differential, promotes, inhibits?
Not selective
Differential for hemolysis patterns
Promotes many bacteria
Inhibits none
Eosin methylene blue: selective, differential, promotes, inhibits?
Selective - dyes inhibit growth
Differential - lactose fermentation, purple or metallic green
Promotes - enteric gram negative rods
Inhibits - gram +
Mannitol salt: selective, differential, promotes, inhibits?
Selective - high mannitol (5%) inhibits growth
Differential - mannitol fermentation, yellow around colonies
Promotes - gram positive staph
Inhibits - gram negative
MacConkey: selective, differential, promotes, inhibits?
Selective - bile salts and crystal violet inhibit growth
Differential - lactose fermentation, dark pink colonies due to pH indicator
Promotes - gram negative
Inhibits - gram positive
Beta hemolysis is indicated by what on the plate?
Clear zone around the colonies
_________ _________ cannot survive in the presence of oxygen
obligate anaerobes
____________ ____________ cannot survive in the absence of oxygen
obligate aerobes
Anaerobes/aerobes can survive in the presence/absence of oxygen if they are what?
facultative
Obligate anaerobe common in abdominal abscesses?
Bacteroides fragilis
Obligate anaerobe that is the cause of tetanus?
Clostridium tetani
Why is O2 lethal?
Auto-oxidation of flavines generates the toxic superoxide radical
-O2
FADH2 + O2 –> FAD + -O2 + H+
Anaerobes lack critical enzymes to get rid of what? What are these two enzymes?
-O2
Superoxide dismutase
Catalase
What are the reactions catalyzed by superoxide dismutase and catalase? Which type of bacteria lack these enzymes?
2 -O2 + 2H+ –> H2O2 + O2
2 H2O2 –> 2 H2O + O2
Anaerobes lack these enzymes
High oxygen tension (hyperbaric chamber) can be used to combat what type of infections?
Anaerobic infections
What obligate aerobe is the cause of (some?) nosocomial infections?
psuedomonas aeruginosa
What obligate aerobe was developed for biological warfare?
Bacillus anthracis
Why do aerobes require oxygen? How do they make triose phosphates?
They lack *phosphofructokinase so they can’t generate enough energy from glycolysis
Require Kreb’s cycle
Pentose shunt
What does phosphofructokinase do in glycolysis?
Converts F6P to F1,6BP which is then converted to glyceraldehyde 3P
________ is essential as a cofactor for many enzymes. What specific type of enzymes (2)?
Iron
Sulfur-containing and electron carriers
Most iron in the environment exists in what state? Most iron in cells?
Ferric Fe3+ state as insoluble hydroxides, carbonates, and phosphates.
Iron in the cells is bound to cellular proteins.
What are siderophores?
Fe3+ specific ligands
Describe bacterial iron transport systems:
Membrane receptors bind siderophores (unique receptor for each siderophore)
Transporter proteins then take up the complex and move into the cell (unique transporter for each complex)
Fe3+ is then reduced to Fe2+, which is usable
Iron uptake systems are redundant. How many distinct systems are there in E. coli?
4
Loss of only the ___________ ___________ iron uptake system may lead to loss of the ability to cause disease
Highest affinity
Low affinity iron uptake systems are suitable for growth in _______ but not in ________
The lab
The body
Can metabolic differences in animals and bacteria be exploited for therapy?
No, but they are helpful for diagnosis
E. coli and shigella dysenteriae, which ferments lactose and is a normal component of the body?
E. coli
Shigella dysenteriae, is it resistant to acid? How could decreased food consumption lead to infection?
No
Decreased food consumption leads to decreased gastric acid secretion
Enterobacter aerogenes vs E. coli: which produces acetoin and which is usually present in field water?
Enterobacter aerogenes
Yeast converts ___________ ______ to ethanol. Is this medically useful?
Pyruvic acid
Nope but beer
Some bacteria use pyruvic acid to make what? (relevant for cheese)
proprionic acid and CO2
What determines bacterial shape and protects the cytoplasmic membrane?
Peptidoglycans
What is the most important difference between bacteria and humans?
Peptidoglycans
What gives bacterial cell walls its rigidity and strength? (only true bacteria have it)
Peptidoglycans
Peptidoglycan thickness is determined by what?
Genetically determined vertical cross-linking
Many antibiotics interfere with what aspect of bacteria?
Peptidoglycan synthesis
What are the three steps of peptidoglycan synthesis?
Peptidoglycan monomer
Extension of the glycan chain
Cross-linking of the glycan strands
What are the two peptidoglycan monomers?
NAG: N-acetyl-glucosamine
NAM: N-acetyl-muramic acid
Peptidoglycan monomer: First NAM is made from what? What is this step blocked by?
NAM is made from NAG
Blocked by Fofsomycin
Peptidoglycan monomer: Second, NAM requires the addition of what? What is this step blocked by?
Requires the addition of a pentapeptide
Blocked by Cycloserine
Metabolic inhibitors: fosfomycin antagonizes what?
phosphoenolpyruvate
Metabolic inhibitors: cycloserine antagonizes what?
D-alanine
Extension of the chain: what happens and what inhibits this step?
NAG and NAM-pentapeptide are linked together in an alternating chain
Blocked by Bacitracin
Cross-linking step: what happens and what is this step blocked by?
Pentapeptide on one NAM is cross-linked to the pentapeptide on another NAM
Blocked by many antibiotics including beta-lactams (penicillins, cephalosporins) and vancomycin
Gram + bacteria have thicker cell walls because of more what?
Vertical cross-links
Gram + cell walls are porous. What are the size of the pores and what size molecule can fit through?
1.1nm
12,000 MW
Growth of a culture diluted into fresh medium can be divided into 3 phases of growth:
Lag
Exponential
Stationary
Doubling time (mean generation time): smaller is faster or slower?
Smaller is faster
Instantaneous growth rate (alpha): larger is faster or slower? How does it relate to doubling time?
Larger is faster
Doubling time = 0.69(1/alpha)
Exponential growth rate (mu): larger is faster or slower? How does it relate to doubling time?
Larger is faster
Doubling time = 1/mu
Psychrophiles: temperature range and example?
-5 to 30 degrees C
Listeria monocytogenes causes disease from inadequately pasteurized cheese
Mesophile temperature range
10 - 40 degrees C
Grow well at body temp
Thermophile temperature range, example
25 to 110 degrees C
Thermus acquaticus: source of Taq polymerase for PCR
