Microbiology Quiz 3: Lectures 19-26

mesophile

optimal growth at mid-range temperatures, associated with warm-blooded animals

psychrophiles

growth optimal at <20 degrees C, inhabit permanently cold environments, need liquid water

psychrotolerant

growth optima > 20 degrees C, but can grow at 0; more common than psychrophiles

adaptations for psychrophily (cold)

• increase unsaturated fatty acids to increase membrane fluidity

• more alpha-helices (protein structure) to increase fluidity

thermophiles

growth optima >45 degrees C (hot springs, volcanos)

hyperthermophiles

growth optima >80 degrees C (geothermal/hydrothermal vents)

theoretical limit for growth

~150-180 degrees C (no eukarya can grow above 65; no bacteria can grow above 95)

adaptations for life at high temperatures

• changes in protein structure/ membrane structure to increase stability

  • Saturated fatty acids, isoprene units and lipid monolayers (Archaea)

adaptations related to pH

• changes in membrane structure to increase stability

beta-lactams

target cell wall synthesis; inhibits synthesis of peptidoglycan, which causes cell lysis (includes penicillin)

rifampicin

targets transcription via bacterial RNA polymerase

which antibiotic (s) target translation?

tetracyclines and chloramphenicol

destroy antibiotic

add functional groups (beta-lactams, acetyl transferases)

prevent entry of antibiotic

reduced expression/loss of porins = intrinsic resistance

mutate target to reduce binding of antibiotic

MRSA, replaces target protein with resistant version

remove antibiotic

efflux pumps use ATP/proton gradients to remove antibiotics from the cell

prevent binding of antibiotic

cationic peptides won’t bind to positive charges

redox rxn

electron exchange from donor to acceptor

anabolism

build molecules up, uses energy

catabolism

breaks molecules down, releases energy

free energy (G)

energy available to do work

exergonic reaction

ΔG < 0, energy released

endergonic reaction

ΔG > 0, energy goes in

oxidation

electron is removed

reduction

electron is added

reduction potential

tendency to donate electrons

ΔE

acceptor (lower one) - donor (higher one); positive is more favorable

Gibbs free energy equation

ΔG = -nFΔE; negative is favorable

ALWAYS reactants

electron donors/acceptors

reducing power

ability to transfer e-, required to perform many metabolic reactions

photo

energy from light

chemo

energy from chemical reactions

organo

electron donor is organic (has C-H bonds)

litho

inorganic (H2S, NH4+)

heterotroph

organic (carbon source not CO2)

autotroph

CO2

Glycolysis

• glucose is electron donor

• no o2 required

• generates 2 ATP, 2 NADH, 2 pyruvate

pentose phosphate pathway

• generates NADH

• generates precursors for anabolic pathways and nucleotides

Entner-Doudoroff Pathway

• uses glucose adjacent carbon sources

• shortcut for glycolysis

• needed for gluconate utilization (absent from humans)

fermentation

puts e- from NADH back onto a breakdown product of the original substrate

Citric Acid Cycle

• oxidation of glucose, e- stored in NADH

• 3 CO2, 1 ATP, 1 FADH2, 4 NADH

• required for anabolic processes as intermediates are used for biosynthesis

• required for catabolism by many heterotrophs

PTS System

brings in glucose to the cytoplasm

proton motor force

relative accumulation of protons outside the cell

flavoproteins

• accept e- and H+ but only donate e-

• contain flavin group

quinones

• small, hydrophobic, non-protein molecules

• accept e- and H+ but only donate e-

iron-sulfur proteins

• accept and donate e- via the Fe-S clusters

• proteins that contain Fe-S clusters

Cytochromes

• proteins that contain heme prosthetic groups

• accept and donate e- via the Fe in heme

• shuttle molecules

complex I

• Net 4 H+ pumped across membrane

• FMN reduced to NADH

• FMH2 reduces Fe/S protein

ubiquinone (coenzyme Q)

• reduced by 2H from quinone to a quinol

• long hydrophobic isoprenoid tail (anchored to membrane)

• hydrophobic uncharged head group (can flip head group from one side of membrane to the other)

• travels freely through the membrane

quinones

• cycle b/w complexes I, II, III

• coenzyme Q replaced by all complexes

• transfers 2 H+ for each 2e- it accepts

• net transfer of e- to cyt bc

complex II

• FAD reduced by succinate (2e- and 2H+)

• FADH2 reduces coenzyme Q (2e-)

complex III

• accepts e- from quinone

• can donate e- to cyt c, recycle e- to quinones

cytochrome c

• located in periplasm

• shuttles e- to complex IV

Complex IV

• transfers e- to o2 (terminal electron acceptor)

• 2H+ consumed in cytoplasm, 2 H+ pumped across membrane

ATP Synthase

• protein complex that converts proton motive force into ATP

• generates 1 ATP for every 3 H+

• works like a water turbine

e- transport chain

• oxidize 1+ electron donors

• e- carriers have increasingly more + E0 along chain

• Build PMF by 1+ mechanisms

• net = reduction of terminal electron acceptor and generation of PMF