04_Bacterial Metabolism Flashcards
These cards are complete and contain info from lecture and notes.
These cards are complete and contain info from lecture and notes.
Know: substrate level phosphorylation, oxidative phosphorylation, aerobic and anaerobic
Know: substrate level phosphorylation, oxidative phosphorylation, aerobic and anaerobic
What is the glyoxylate shunt
- shunt within the krebs cycle that uses acetylCoA to shunt isocitrate to malate
- This is used when acetylCoA is generated from acetate, which occurs when bacteria grow on a fatty medium rather than a sugar medium
Are there examples when the electron transport chain is still used anaerobically?
- Some bacteria can us NO3- instead of O2 in the ETC.
* NO3 is reduced to N2.
Note: in the ETC, H are pumped in the space between the inner membrane and the cell wall. H then use the ATP synthase (like in mammals). H also use anti-ports that expel unwanted substances from the bacteria (like antibiotics)
Note: in the ETC, H are pumped in the space between the inner membrane and the cell wall. H then use the ATP synthase (like in mammals). H also use anti-ports that expel unwanted substances from the bacteria (like antibiotics)
There is a basic chart comparing respiration vs fermentation on page C-3. The info is basic.
There is a basic chart comparing respiration vs fermentation on page C-3. The info is basic.
What are the features of lactic acid production?
What are examples of bacteria that use this pathway?
- reduces pH
- used in pickles, sauerkrauts, and cheeses
- Lactobacilli (edible ferments)
- Streptococcus pyogenes (strep throat)
What is the relevance to pre-puberty, women with menses, and post-menopausal women?
- the reduced pH protects against Candida albicans
* Pre-puberty and post-menopausal women do not have lactobacilli and the pH of their vaginas are neutral
Explain Butyric Acid Fermentations (also butanol-acetone fermentations)
What is the classic bacteria?
What are the products?
What is a diagnostic feature?
- Clostridia
- Forms butyric acid, acetic acid, CO2, H2, and small amounts of alcohols
- If H2 or butyric acid is present (air bubbles in tissues) ==> diagnosis Clostridia
- Butyric acid has a distinctly unpleasant odor (ex: gangrene)
When is Clostridium protective?
• can protect against hemorrhagic E. coli strains (hemorrhagic colitis)
Explain propionic acid fermentation.
What bacteria?
What is the signature feature of propionic acid fermentation?
What is a common food product that uses this fermentation?
What is a clinically relevant event that uses this fermentation (think embarrassed teenager)?
- propionic acid bacteria: corynebacteria: propionibacterium and bifidobacterium.
- Signature: ferment lactate ==> acetic acid, CO2, and propionic acid
- Used in swiss cheese (CO2 produces bubbles)
- Propionibacteriium acnes are involved with acne
Explain mixed acid fermentations by enteric microbes.
What are some products?
How is this phenomenon used clinically?
• microbes in the intestines use many distinct and overlapping pathways to ferment due to competition (lots of bacteria, very little space)
• succinate, lactate, ethanol, formate ==> H2 and CO2, acetate, acetoin, butanediol
o see details on page C-4 bottom. However, details are not needed currently
• products of a bacteria fermentation may be diagnostic
o example:
• shingella produces formic acid, not H2
• Salmonella produces formic acid and H2
Explain when 2,3 butanediol and acetoin are used clinically?
• some bacteria produce butanediol and its intermediate acetoin.
• These are neutral pH (low acid)
• May be used to distinguish…
o non-fecal enteric bacteria (butanediol formers, such as Klebsiella and Enterobacter)
o fecal enteric bacteria (mixed fermenters, such as E. coli, Salmonella, and Shigella
Explain ethanol fermentation.
What microorganisms use ethanol fermentation?
What are the products?
- performed by yeast: Saccharomyces cerevisiae
- Performed by fungus: Candida albicans
- Pyruvate ==> CO2 and ethanol
- CO2 gas provides mild acid, however, in alkaline tissues CO2 becomes carbonate
What is the Stickland Reaction?
What bacteria uses the Stickland Reaction?
What are the substrates?
• clostridia • pairs of amino acids alternatively act as the electron donor and acceptor o Alanine (donor) o Glycine (acceptor) • Occurs in putrefying wounds.
What determines a microbes relationship with oxygen?
- respiration vs fermentation
* ability to detoxify oxygen radicals
Explain Obligate aerobes.
- respiration throught the electron transport chain
* no enzymes for fermentation
Explain how Pseudomonas aeruginosa are considered obligate aerobes.
- cannot ferment sugars
- can respire in the absence of oxygen using nitrate NO3-
- Note: respiration in the absence of oxygen is called anaerobic respiration
What is anaerobic respiration?
• respiration in the absence of oxygen
Explain facultative anaerobes.
- grow with or without oxygen
- Have both respiration and fermentation enzymes
- Note: more ATP comes from respiration
- Ex: E coli and Staphylococcus
Explain Obligate anaerobes.
What respiration byproducts are harmful to anaerobes?
Where are these found in the body?
- no respiration, only fermentation
- require reducing conditions to grow, and cannot grow in the presence of O2
- Produce H2O2 and superoxides (toxic to the bacteria) due to subsequent ROS
- Lack Catalase: a heme containing enzyme that breaks down H2O2
- Lack Superoxide Dismutase: breaks down superoxide
- Example: Bacteroides Fragilis
- Found deep in gut, abscesses, and deep puncture wounds
What is Catalase?
What is Superoxide Dismutase?
• Catalase, a hemoprotein enzyme present in most aerobes which decomposes H2O2.
o 2 H2O2 → H2O + O2 [gas]
• Superoxide dismutase breaks down superoxide, a highly reactive free radical reactive form of oxygen (O2-), formed by flavoenzymes.
o 2O2- +2H+ →H2O2+O2
Explain Aerotolerant anaerobes.
- do not have respiration capability, but can break down Oxygen radicals and are therefore indifferent to Oxygen
- Lactic acid species: Lactobacillus and Streptococcus
- Some Clostridium
Explain Microaerophiles.
- prefers 5% oxygen environments
* example: Campylobacter jejuni grows in the intestines where there is modest O2
