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Microbiology > Growth and metabolism > Flashcards

Growth and metabolism Flashcards

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Biology 101 flashcards
0
Q

Limits on bacterial growth

A 
Exhausted nutrients
Accumulation of toxic byproducts
Antibiotics from neighboring
Immune function
Environmental (ex physical barriers)
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1
Q

Generation time

A

Time to double population
Range from <30 min - 20 hours

Only relevant during exponential phase

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2
Q

Major nutrient requirements

A 
Carbon - both oxidation and cell structures
Nitrogen - protein and DNA
Phos - phospholipids and DNA
Sulfur - proteins
Iron - enzyme cofactor (metabolism)
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3
Q

Carbohydrate sources

A

Provides energy (ATP) and C for growth
Use depends on specific degradative enzymes
- can be diagnostic

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4
Q

Amino acids as nutrients

A

Sources of C, N, S
Proteins too big -> secrete proteases -> absorb acids and small peptides
Some require specific acids (no enzymes to create)
Some can use ammonia (NH4) and nitrate

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5
Q

Nucleic acids as nutrients

A

Sources of C, P, N

Secrete nucleases -> absorb DNA and RNA

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6
Q

Phospholipids as nutrients

A

Provide C, N, P
Secrete phospholipases
-> host cell lysis due to degradation
- tied to Fe metabolism (lysed cells release)

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7
Q

Iron metabolism

A 
Necessary for enzymes (oxidative)
Key site of host-pathogen interaction
 - host factors bind/sequester iron
 - bacteria makes
  - phospholipase - lyses cells to release Fe
  - siderophores/chelators to extract
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8
Q

Growth factors

A 
Not metabolized for energy
Used to make essential metabolites
Diagnostic
 - E coli - only requires glucose, NH4 and ions
 - others "fastidious"
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9
Q

Temperature requirements

A

Most pathogens grow best at 37C (body core)
Most env’t grow best at 22-30C (room temp)

Exceptions

  • Mycobacterium leprae -> growth in colder body areas (hands vs core)
  • Legionella - grows at high temp (45C)
  • Listeria - grows at low temp (4C = refrigerator -> food poisoning)
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10
Q

Physical requirements for growth

A

Temp (separate slide)
pH - usu 6-8 with 7.4 optimal (body)
- Clostridium botulinum - grows less in acid
Osmotic pressure
- cell wall helps withstand pressure changes
- high salt or sucrose inhibits growth (pickles, jam)

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11
Q

Growth in lab

A

Peptone broth + glucose
- peptone = meat + pepsin = protein and aminos
Blood agar - supports almost all pathogens

Agar - non-digested sugar - solidifies
- need solid medium to isolate colonies

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12
Q

Measurement of bacteria

A

Optical density - proportional to concentration
- spectrophotometer or naked eye turbidity
- limit is 10’6/mL
Metabolic activity (CO2 or ATP production)
- sensitive for bacteremia
Direct count - chamber in microscope
- insensitive (10’5/mL) -> any visible bacteria indicates infection
- includes both living and dead cells
Plate count - most common, accurate
- after serial dilution, 24h incubation
- yields colony forming units (CFUs)

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13
Q

Growth curves

A

Usu log scale number/mass vs time
Lag phase - metabolic activity, mass and size inc but no division
- adaptation to new medium -> new RNA, proteins
Exponential phase - binary fission
- constant generation time (bacteria, medium, temp, etc)
- “balanced growth” all components double in same time (mass, DNA)
Stationary phase - steady state of death and growth
- can last days-years
- usu 10’9/mL for pathogens in test tube
Death phase - death>growth, can last years
- unusual morphology

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14
Q

Glycolysis

A

aka Embden-Meyerhof pathway

Glucose + 2 ATP + NAD -> pyruvate + 4 ATP + 1 NADH

ATP from substrate-level phosphorylation (direct)

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15
Q

TCA cycle

A

aka tricarboxylic acid cycle, Krebs

Produces “reducing equivalents” aka NADH -> ETC

Glyoxylate shunt: fatty acit -> acetate -> AcCoA -> NADH

16
Q

Eletron transport chain

A

Sim to mitochondria
Cytochromes in inner membrane
NADH -> electron acceptor -> proton gradient ->
ATP via oxidative phos

Electron acceptors:

aerobic: O2 -> H2O
anaerobic: not O2, ex NO3 -> N2

17
Q

Fermentation overview

A

Glycolysis but no TCA and ETC (no enzymes, no O2)
Pyruvate + NADH -> NAD+ + reduced fermentation product

ATP - much less than respiratory chain (substrate level only)

Fermentation product excreted (most carbon)

18
Q

Lactic acid fermentation

A

Lowers pH - inhibits other microbes

Ex:
Lactobacilli in intestine, vagina -> inhibit Candida
- also in yogurt, cheese, etc
Strep pyogenes (strep throat)

19
Q

Butyric acid fermentation

A

Clostridium!!
- also produce butenol-acetone, acetic acid, CO2, H2, EtOH…

Distinctive odor
Protective against some pathogens (E coli)

20
Q

Propionic acid fermentation

A

Lactic acid -> propionic acid + acetic acid + CO2
Corynebacteria, Propionibacteria, Bifidobacteria

Swiss cheese
Propionibacteria -> deep follicles -> acne

21
Q

Mixed acid fermentation

A

Enterobacteriae (Gram (-) bacilli)
Pyruvate -> AcCoA + formic acid
- formic acid -> H2 + CO2
- AcCoA -> EtOH + acetic + succinic (“mixed acid”)

Ex:

  • Salmonella -> H2 gas (gas gangrene)
  • Shigella - lacks enzyme - formic acid builds up
  • E coli
22
Q

Butanediol fermentation

A

Mixed acid fermentation -> acetoin -> 2,3 butanediol
(less acidic product)

Non-fecal enteric bacteria (Klebsiella, Enterobacter)
vs acidic fecal (E coli, Salmonella, Shigella)

23
Q

Ethanol fermentation

A

Pyruvic acid + NADH -alcohol dehydrogenase> EtOH + CO2

Saccharomyces cerevisiae -> beer, wine
(CO2 -> gas in slight acidity)
Candida albicans -> fungal infections (no gas due to alkalinity)

24
Q

Strickland reaction

A

Clostridia in wounds
Paired amino acid fermentation (one donor, one acceptor)
-> decarboxylated acids
-> odor, volatile

25
Q

Obligate aerobes

A

Require O2, all ATP via O2 respiration
(no fermentation enzymes)

Mycobacterium tuberculosis -> upper lobes of lung
Pseudomonas aeruginosa - not technically correct definition, no fermentation but can have NO3 respiration

26
Q

Facultative anaerobes

A

Both respiration and fermentation
Grow fastest with O2 (more ATP from fermentation)

Many pathogens
E coli
Staphylococcus

27
Q

Obligate anaerobes

A

Only fermentation
Oxygen toxic - require reducing conditions
- flavin enzymes -> H2O2 -> superoxide (O2-), ROS -> damage
- lack catalase (for H2O2) and superoxide dismutase

Ex Bacteroides fragilis (intestine, abcesses)

28
Q

Aerotolerant anaerobes

A

Lack respiratory system
Can survive O2 exposure but prefer anaerobic

Lactic acid bacteria
- Lactobacilli
- Streptococcus
Clostridium (tetani, botulinum)

29
Q

Microaerophiles

A

Aerotolerant only at low concentrations (ex 5% vs 20% atm)

Campylobacter jejuni

30
Q

Anaerobic tissues

A

Mouth, GI
Surface tissue if other bacteria or host is using up O2
Culture if reducing medium (ex cysteine)

31
Q

Glucose fermentation

A

Usu GI microbes
(E coli, Klebsiella, Salmonella, Shigella, Citrobacter)

vs lactose - requires additional enzyme to cleave
only E coli and Klebsiella, Citrobacter slow

Pseudomonas doesn’t use either…

Microbiology (23 decks)

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