List agricultural applications of microbiology.
Plant cell transformation, biological control (weeds, microbial insecticides), food fermentation, nitrogen cycle/nodule formation in legumes, plant pathogens, natural/engineered disease resistance, biodegradation of pesticides, methane production & agricultural waste management.
List major environmental microbiology applications.
Aquatic microbiology, drinking water microbiology, soil microbiology, airborne transmission/air quality, biodegradation & biodeterioration, bioremediation, industrial effluent treatment, biofilms & biofouling.
Industrial applications of microbiology?
Pulp/paper, industrial fermentations, bacterial metabolites, antibiotic biosynthesis, vitamins & related biofactors.
Food‑related applications?
Brewing/wine making, dairy products, spoilage & preservation, quality control, enzymes in biotechnology, lactic acid bacteria.
Genetic applications of microbiology?
Recombinant DNA, site‑directed mutagenesis, genetic transformation, virus vaccines, transgenic plants/animals, environmental biotechnology, gene regulation & gene therapy.
Medical microbiology themes?
Disease/pathogenesis, emerging infections, enteropathogenic bacteria, waterborne diseases, foodborne diseases, STDs, viral disease, immunology.
Why are prokaryotic cells described as “sophisticated and dynamic”?
Prokaryotes have a highly organized spatial and temporal structure.
What are the major archaeal phenotypes?
- Methanogens: Produce methane as a metabolic byproduct.
- Extreme halophiles: Thrive in very salty environments.
- Extreme thermophiles: Prefer very high temperatures.
Describe the structure and components of a bacterial flagellum.
A bacterial flagellum has three major parts:
- Filament
- Long, whip‑like structure made of the protein flagellin.
- Multiple flagellin chains wind around a hollow core. - Hook
- Flexible curved connector that links the filament to the basal body. - Basal body
- Anchors the flagellum to the cell wall & membrane.
- Acts as the rotary motor.
How does the basal body differ between Gram‑positive and Gram‑negative bacteria?
Gram‑negative:
- Four rings (L ring in outer membrane, P ring in peptidoglycan, MS and C rings in the inner membrane).
- More complex structure.
Gram‑positive:
- Two rings (MS and C rings only).
- Thicker peptidoglycan eliminates need for outer rings.
How do bacteria move using flagella?
- Movement results from rotation of the flagellum.
- Counterclockwise rotation → a run (smooth forward movement).
- Clockwise rotation → a tumble (random reorientation).
- A “switch” in the basal body changes rotation direction.
- Motility responds to attractants/repellents (chemotaxis).
- Some species (e.g., Vibrio cholerae) have sheathed flagella for protection.
What is the bacterial cell wall, and what is peptidoglycan made of?
Cell wall: Rigid outer layer that determines shape and prevents osmotic lysis.
Peptidoglycan consists of alternating sugars:
- NAG (N‑acetylglucosamine)
- NAM (N‑acetylmuramic acid)
Adjacent rows are cross‑linked by tetrapeptide side chains and sometimes additional cross‑bridges.
What destroys peptidoglycan, and why is this important?
Lysozyme cleaves the NAG–NAM backbone.
Penicillin inhibits cross‑linking of peptidoglycan.
What are porins?
Channel proteins allowing uptake of nucleotides, sugars, peptides, amino acids, vitamins, Fe.
Describe the cytoplasmic membrane’s structure and functions.
Phospholipid bilayer + integral/peripheral proteins (“fluid mosaic model”).
Functions:
- Selective permeability.
- Location of metabolic reactions.
- Site for energy generation and transport.
- Houses active and passive transport systems.
Cytoplasm contains what structures?
Gas vesicles, carboxysomes, chlorosomes, magnetosomes, granules/globules, ribosomes, nucleoid, multienzyme complexes.
What characteristics define living systems?
Metabolism, reproduction, differentiation, communication, movement, and evolution.
Difference between heterotrophs & autotrophs?
Heterotrophs require one or more organic carbon.
Autotrophs use CO₂ as the primary carbon source
What is proton motive force (PMF)?
PMF is the potential energy stored in a proton gradient across the membrane, generated when protons are pumped outward.
- Outside becomes positively charged and often more acidic.
- Drives ATP synthesis, transport, and motility.
How do membrane potential and pH potential differ?
Membrane potential (Δψ): Due to separation of charge across membrane. Difference in charge (voltage).
pH potential (ΔpH): Due to difference in proton concentration.
Bacteria cannot maximize both simultaneously — they balance them depending on environment.
What defines neutrophiles, acidophiles, and alkaliphiles?
Neutrophiles: pH near 7; most PMF from Δψ.
Acidophiles: pH 1–4; PMF from ΔpH.
Alkaliphiles: pH > 9; PMF from Δψ since external pH is too high for ΔpH.
What are the central metabolic pathways, and what do they produce?
Three pathways:
- EMP (Glycolysis)
- Pentose Phosphate Pathway
- Entner–Doudoroff (ED) Pathway
All convert glucose → phosphoglyceraldehyde, then → pyruvate.
Pyruvate enters respiration (TCA cycle) or fermentation.
What characterizes the Entner–Doudoroff (ED) pathway?
- Common in aerobic Gram‑negative bacteria.
- Not found in most anaerobes.
Produces less ATP than EMP. - Some bacteria (e.g., Pseudomonas) rely solely on ED.
- Reaction: Glucose + NADP⁺ + NAD⁺ + ADP + Pi →
2 pyruvate + NADPH + NADH + ATP + 2H⁺
What is lithotrophy, and what compounds can lithotrophs oxidize?
Lithotrophs obtain energy by oxidizing inorganic compounds, such as:
H₂, CO, NH₃, NO₂⁻, H₂S, S⁰, thiosulfate, Fe²⁺
Most use CO₂ as carbon source (autotrophic).
Some can switch to heterotrophy (facultative).
