Microbial Metabolism and Cell Structure Review

Flashcards covering key vocabulary and concepts related to microbial metabolism, cell structure, and mechanisms studied during lectures.

Macromolecule with largest physiological impact if absent from a bacterial cell?

peptides

What macromolecule's synthesis is directly affected by nitrogen limitation?

Proteins.

What effect does a mutation in an enzyme's active site typically have?

Decreases substrate binding affinity and reduces reaction rate.

Two enzymes catalyze the same reaction in two different bacteria. Enzyme A: Km = 0.1 mM and Enzyme B: Km = 5 mM. At a substrate concentration of 0.2 mM, which enzyme will be closer to Vmax?

Enzyme A with Km = 0.1 mM.

A bacterial enzyme involved in glycolysis is exposed to a negative allosteric inhibitor. The of the enzyme to convert substrate to product is unchanged in the presence of the inhibitor. What change is expected after inhibitor addition (Km and Vmax?

Unchanged Vmax and increased Km.

If an enzyme's Vmax decreases but Km remains unchanged, what does this suggest?

Decreased catalytic efficiency.

What does a sigmoidal velocity vs substrate curve indicate about an enzyme?

It is allosterically regulated.

Under what condition would an enzyme activated by AMP be most active?

Low energy charge with high AMP.

What happens to glucose uptake if a bacterium lacks Enzyme 1 of the PTS system?

Glucose uptake fails entirely.

What happens to CAMP levels when glucose is removed from a culture?

CAMP levels increase, enabling alternative sugar use.

Which species produces more ATP under identical conditions?

Species A using EMP glycolysis.

During a lag phase, what metabolic event occurs?

Enzyme synthesis for secondary carbon source.

What happens when a bacterium lacks pyruvate kinase during glucose growth?

PEP accumulates and glucose uptake via PTS is impaired.

What effect do high ATP and citrate concentrations have on glycolytic flux?

Decreases due to allosteric inhibition.

If oxaloacetate is depleted, what happens to the TCA cycle?

It slows unless anaplerotic reactions replenish OAA.

A bacterium grows solely on acetate as a carbon source, which pathway is active?

Gluconeogenesis.

With one bacterium having a complete TCA cycle and another incomplete, which one produces fewer reducing equivalents?

The second bacterium.

Why does fermentation yield less ATP than respiration?

No electron transport chain is used.

What mainly determines ATP yield from an Electron Transport Chain?

Proton motive force.

What is expected with a mutant lacking PEP but with a non-PTS glucose transporter?

Impaired glycolysis and reduced TCA flux.

What metabolic strategy supports long-term survival in nutrient-poor soil?

Flexible respiration and carbon conservation.

What changes when a bacterium switches from oxygen to nitrate respiration?

The terminal electron acceptor changes.

Why does aerobic respiration yield more ATP than anaerobic respiration?

Oxygen has a higher redox potential.

Which organism is using anaerobic respiration rather than fermentation?

Uses nitrate as an electron acceptor.

What does a growth curve showing initial rapid growth followed by a plateau indicate?

Cells sequentially utilize two different carbon sources.

Which curve represents a strain that has lost catabolite repression?

Curve 1.

What best explains the growth pattern for a mutant strain that lost catabolite repression?

Simultaneous utilization of glucose and lactose.

What molecular mechanism is most likely disrupted in a mutant that cannot metabolize acetate?

Isocitrate lyase activity.

What happens to growth on glucose if a bacterium can’t form PEP?

No glucose uptake.

What characterizes Gram-negative bacteria's cell wall structure?

Presence of m-DAP as the 3rd amino acid.

What antibiotic binds PBPs to prevent cross-linking of peptidoglycan?

Vancomycin.

What enzyme links glycan chains during peptidoglycan synthesis?

Transglycosylase.

What function does bactoprenol serve in bacteria?

Transporting peptidoglycan precursors across the membrane.

What results from an increase in D,D-transpeptidase activity?

Reduced stress tolerance of the cell wall.

What confers resistance to lysozyme in peptidoglycan?

O-acetylation.

Where is lipid A synthesized in Gram-negative bacteria?

Cytoplasm and inner membrane.

What unusual sugar is found in LPS polysaccharides?

KDO (2-keto-3-deoxyoctulosonic acid).

What is capsule polysaccharide synthesis commonly reliant on?

Activated nucleotide sugars.

What is the consequence of a bacterium lacking a capsule?

Increased susceptibility to phagocytosis.

What role does the MinCE system play in bacterial division?

Oscillating to prevent Z-ring formation at poles.

What does nucleoid occlusion prevent in cell division?

FtsZ polymerization over unsegregated DNA.

What results from a FtsZ mutation preventing polymerization?

Failure of Z-ring assembly.

In which medium does a facultative anaerobic bacterium shows robust growth on acetate?

Minimal medium.

What indicates that a bacterium is engaging in secondary fermentation?

Presence of products like acetate and propionate.

How would oxygen presence change fermentation profiles?

Aerobic respiration would replace fermentation.

What happens if glucose is suddenly removed from a growing E. coli culture?

CAMP levels increase, enabling alternative sugar use.

What is expected from a PEP-deficient mutant strain growing on glucose?

Lack of pyruvate formation.

Which antibiotic inhibits transpeptidation during peptidoglycan synthesis?

Penicillin.

How does cycloserine affect peptidoglycan synthesis?

By inhibiting D-Ala-D-Ala formation.

What is the consequence of a bacterium losing its capsule?

Increased susceptibility to complement.

What does increased D,D-transpeptidase activity lead to during S phase?

Increased 3-3 cross-links.

What does Bacitracin inhibit specifically?

Recycling of bactoprenol.

How does Vancomycin inhibit peptidoglycan synthesis?

By binding to D-Ala-D-Ala termini.

What does the presence of a novel protein secretion channel in a bacteria allow it to do?

Export fully polymerized peptidoglycan strands.

What is the function of isocitrate lyase for bacteria using acetate?

Initiates the glyoxylate shunt.

What is the effect of high energy charge on enzyme activity?

Decreased metabolic activity.

How does a facultative anaerobic bacterium respond to acidic conditions?

Increases saturated and cyclopropane fatty acids.

Why is membrane rigidity increased in acidic environments?

To prevent proton diffusion.

What accumulates if a bacterium cannot utilize acetate?

Excess carbon loss as CO2.

What happens to pyruvate if PEP cannot be formed?

Decreased entry into the TCA cycle.

What affects peptidoglycan synthesis in bacteria?

Antibiotic action on bacterial enzymes.

How does the mutation in bactoprenol lead to sensitivity to phagocytosis?

By preventing O-antigen production.

Why does fermentation yield fewer ATP than aerobic respiration?

Lacks the electron transport chain.

How do PEP and glucose transport relate?

PEP is essential for glucose uptake in PTS.

What role does fatty acid composition play in membrane fluidity?

Determines membrane rigidity or fluidity.

What pathway must be active if a bacterium grows on acetate alone?

Gluconeogenesis.

Why are unsaturated fatty acids crucial at neutral pH?

To maintain membrane fluidity.

What role does FtsZ play during bacterial cell division?

Forming the Z-ring for separation.

What happens to ATP yield when a bacterium switches from aerobic to nitrate respiration?

Terminal electron acceptor changes.

Why does a lack of catabolite repression affect glucose metabolism?

Allows simultaneous utilization of other sugars.

What does the accumulation of UDP-MurNAC tripeptide indicate when using specific antibiotics?

Inhibition of peptidoglycan synthesis.

What enzyme is targeted by Vancomycin during peptidoglycan synthesis?

Penicillin-binding proteins (PBPs).

Why does the TCA cycle stop with oxaloacetate depletion?

Without OAA, the cycle cannot continue.

What advantage does a bacterium gain by increased membrane rigidity under stress?

Protection against environmental insults.

How does a mutant with defective PEP impact glycolysis?

Impaired glycolytic function.

What physiological change occurs with elevated fatty acids in bacterial membranes?

Shift from fluid to more rigid.

What is the role of activated nucleotide sugars in capsule synthesis?

Provides precursors for polysaccharide formation.

What impact does D,D-transpeptidase activity have on cell wall stability?

Helps maintain cell wall integrity.

What does NADH do during aerobic respiration?

Gets oxidized in the electron transport chain.

What indicates robust growth under specific conditions in bacteria?

Successful metabolism of available nutrients.

What does the presence of D-alanine deplete in mutant strains?

Essential for cross-linking in peptidoglycan synthesis.

Why are certain fatty acids preferred in certain environmental conditions?

To maintain optimal membrane fluidity.

What happens to metabolic rates when glucose is the primary carbon source?

Increases metabolic efficiency.

Why does a bacterium utilize anaerobic respiration over fermentation?

Utilizes available electron acceptors effectively.

What cumulative result comes from mutations affecting glucose metabolism?

Reduces overall energy yield.

How do different bacteria adapt to nutrient-poor conditions?

By employing flexible metabolic strategies.

What differentiates primary from secondary fermentation pathways?

Production of different metabolic end products.

What effect does nutrient availability have on bacterial growth dynamics?

Influences growth phases seen in growth curves.