ch.9

Essential Elements & Nutrients

  • Essential elements: C,H,O,N,P,SC, H, O, N, P, S (collectively CHONPSCHONPS) compose 96%96\% of dry weight; other key ions K,Ca,Mg,Fe,Na,ClK, Ca, Mg, Fe, Na, Cl, etc.
  • Macronutrients: needed in large amounts for structure & metabolism.
  • Micronutrients/trace elements: required in minute quantities for enzyme & protein function.
  • Inorganic nutrients: lack combined CC and HH; organic nutrients contain both.
  • Growth factors: pre-formed organics (e.g., vitamins, amino acids) a cell cannot synthesize and must import.

Carbon & Energy Sources

  • Heterotroph: organic CC; Autotroph: fixes CO2CO_2.
  • Energy options → Phototroph (light) vs. Chemotroph (chemicals).
  • Combined categories:
    • Photoautotroph (algae, plants, cyanobacteria).
    • Chemoautotroph: • chemoorganic (energy from organics) • chemolithoautotroph (energy from minerals).
    • Photoheterotroph (purple/green bacteria).
    • Chemoheterotroph: • Saprobe = decomposer of dead matter. • Parasite = lives in/on host.
  • Special type: methanogens 4H<em>2+CO</em>2→CH<em>4+2H</em>2O4H<em>2 + CO</em>2 \rightarrow CH<em>4 + 2H</em>2O (anaerobic Archaea).

Membrane Transport & Osmoregulation

  • Passive (no ATP):
    • Simple diffusion (down gradient).
    • Facilitated diffusion (carrier-specific; saturation & competition).
  • Osmosis (water movement):
    • Isotonic – no net flow.
    • Hypotonic – water enters ⇒ swelling/lysis; walls or contractile vacuoles protect.
    • Hypertonic – water exits ⇒ plasmolysis; basis of salt/sugar preservation.
  • Active (ATP/PMF): carrier-mediated pumps, group translocation, endocytosis (phago/pino) in eukaryotes.
  • Adaptations: halophiles (high salt), facultative halophiles (tolerant), Halobacteria accumulate salt internally.

Temperature Adaptations

  • Cardinal points: minimum, optimum (fastest growth), maximum (denaturation).
  • Psychrophile: optimum <15^{\circ}C (growth to 0∘C0^{\circ}C).
  • Psychrotolerant: optimum 15−30∘C15{-}30^{\circ}C (slow in cold).
  • Mesophile: optimum 20−40∘C20{-}40^{\circ}C; pathogens 30−40∘C30{-}40^{\circ}C.
  • Thermophile: optimum >45^{\circ}C (range 45−80∘C45{-}80^{\circ}C); extreme up to 121∘C121^{\circ}C.

Gas Requirements & Detoxification

  • Toxic oxygen species: singlet O<em>2O<em>2, superoxide O</em>2−O</em>2^-, peroxide H<em>2O</em>2H<em>2O</em>2, hydroxyl OH−OH^-.
    • Neutralized by superoxide dismutase and catalase.
  • Categories:
    • Obligate aerobe – needs O2O_2.
    • Facultative anaerobe – uses O2O_2 when present; ferments without.
    • Microaerophile – requires low O2O_2.
    • Obligate anaerobe – killed by O2O_2.
    • Aerotolerant – ignores O2O_2 (no use, but tolerates).
  • Capnophiles grow best at 3−10%3{-}10\% CO2CO_2.

Other Physical Factors

  • pH: most microbes 6−86{-}8. • Obligate acidophiles need low pH; alkalinophiles thrive in basic soils/pools.
  • Osmotic: osmophiles (high solute); halophiles (salt); obligate vs. facultative forms.
  • Radiation: phototrophs use light; carotenoids/repair enzymes protect against UV/ionizing rays.
  • Hydrostatic pressure: barophiles survive ∼1000\sim1000 atm in deep sea, rupture at surface.
  • Moisture: thin water film required; spores/cysts endure desiccation.

Microbial Relationships

  • Symbiosis: Mutualism (both benefit), Commensalism (one benefits, other neutral), Parasitism (host harmed).
  • Nonsymbiotic: Synergism (co-operation), Antagonism (competition; antibiosis).
  • Biofilms: multispecies, EPS matrix, quorum sensing regulates genes; increase resistance & pathogenicity.

Growth & Population Dynamics

  • Binary fission sequence → DNA replication, septum, two daughters.
  • Generation (doubling) time: constant under favorable conditions ⇒ exponential 2n2^n increase.
  • Batch culture curve:
    1. Lag (adaptation).
    2. Log (exponential) – highest susceptibility to drugs.
    3. Stationary – nutrient depletion/waste accumulation.
    4. Death – exponential decline (some persisters remain).
  • Chemostat supplies fresh nutrients & removes waste to maintain continuous log phase.

Measuring Growth

  • Viable plate (CFU) counts – serial dilution & plating.
  • Turbidometry – optical density correlates with cell mass.
  • Direct counts – microscopy with cytometer; Coulter counter; flow cytometer (size & live/dead discrimination).
  • Culture-independent: PCR quantification; ATP assays for rapid microbial load estimation.