microbial physiology and metabolism

Question 1

Elements required for cell components

Answer 1

Macroelements (required in larger amounts)
C, O, N, H, S, P
components of carbohydrates, lipids, proteins
and nucleic acids

K, Ca, Mg, Fe
exist as cations and play many roles, including
cofactors of enzymes

Trace elements (required in smaller amounts)
Mn, Zn, Co, Mb, Ni, Cu
mainly needed as cofactors of enzymes

Question 2

Sources of Energy

Answer 2

Phototrophs-Light

Chemotrophs-oxidation of organic or inorganic compounds

Question 3

Sources of Reducing Equivalents

why are these needed?

Answer 3

Need electron donors for electron transport chain (energy production)
redox rxns (includes energy production)
biosynthesis in autotrophs (from CO2)

Lithotrophs- reduced inorganic molecules
Organotrophs- organic molecules

Question 4

Sources of Carbon/ methods of getting it

Answer 4

Autotrophs- CO2 main/only source

Heterotrophs- reduced, preformed organic molecules

Question 5

Major Nutritional Types of pathogens

Answer 5

Chemoorganotrophic heterotrophy

chemical energy source
organic electron donor
organic carbon source

Question 6

N source

Answer 6

amino acids, ammonia nitrate > ammoniaN2

Question 7

P source

Answer 7

Pi

Question 8

S source

Answer 8

sulfate (SO42-) 
reduced sulfur (e.g. cysteine)

Question 9

Growth factors sources

Answer 9

amino acids
purines and pyrimidines
vitamins (small organic molecules)

Question 10

Bacterial oxygen responses

Answer 10

strict anaerobes/aerobes

facualtive anaerobes

Question 11

strict aerobes

Answer 11

perform aerobic respiration only

final electron acceptor is oxygen (reduced to H2O)

Question 12

strict anaerobes

Answer 12

strict anaerobes
perform anaerobic respiration final electron acceptor is an inorganic molecule
examples: nitrate (NO3-), Fe3+

perform fermentation
final electron acceptor is an organic molecule examples: pyruvate (reduced to lactate) acetyl-CoA (reduced to ethanol)

Question 13

facultative anaerobes

Answer 13

can perform respiration if O2 is present and fermentation if it is absent
most medically relevant bacteria

Question 14

the respiratory chain of E. coli

Answer 14

two chains that can be used in high (cyto o) and low (cyto d) oxygen

Question 15

Nutrient uptake methods

Answer 15

facilitated dif

group translocation/ active transport

Question 16

Facilitated diffusion

driven by?

Answer 16

move from higher conc. to lower conc. no energy requirement
permeases = carrier proteins embedded in the plasma membrane

Uptake is driven by intracellular use of the compound

Question 17

Group translocation

Answer 17

Transported substances are chemically altered during the process.

This process uses energy: phosphate bond in phosphoenolpyruvate (PEP). Phosphate from PEP is transferred to several protein
intermediates, eventually becoming linked to the transported substance.

Also called a phosphotransferase system

Question 18

Active transport, types found?

Answer 18

Energy is used to drive the accumulation of a substance, which remains unchanged by the transport process.

Ion-driven transport systems and Binding protein dependent transport systems

Question 19

ion-driven transport systems, limited?

Answer 19

use proton motive force (gradient of protons) by coupling to an energetically unfavorable transport event (concentration of a substance against a gradient)
Common substances transferred are amino acids.
can be saturated

Question 20

Binding protein-dependent transport systems
mechanism and common substances?
saturation?

Answer 20

use membrane proteins that form a channel and drive substances through the channel using the energy from ATP hydrolysis.

Common substances transferred are sugars and amino acids.
can be saturated

Question 21

Iron Uptake

Answer 21

• ferric iron is very insoluble so uptake is difficult
• microorganisms use siderophores to aid uptake
• siderophore complexes with ferric ion
• complex is then transported into cell

Question 22

Nutritionally fastidious, examples?

Answer 22

organisms have complex needs
and can only grow in association with the human body or in
complex culture medium (example: blood agar).
Staphylococci and Streptococci

Question 23

obligate intracellular parasites

Answer 23

require intracellular host

Question 24

Microbial growth and resting states
stages? why?
growth in real world?
variable rates? 
stress responses? 
can damage occur when not growing? 
what can some bac do when they stop growing?

Answer 24

lag>exponential>stationary
due to the use of resources

Growth in real-world is suboptimal
variable growth rates for different organisms

Stress responses protect bacteria
Still cause damage to host when not growing: immunogenic/ toxin production

Some bacteria sporulate when they stop growth

Question 25

Mechanisms of adaptation

Answer 25

• Maximize efficiency in using energy and resources

* Respond to changes

Question 26

The result of regulation:

Answer 26

pathways can be switched on and off

pathways can be turned up or turned down

Question 27

How is control established?

Answer 27

1. Control of enzyme activity

2. Control of the number of enzyme molecules

Question 28

Allosteric regulation of enzymes

what do these modify?

Answer 28

control enzyme activity level

All enzymes have active sites (for catalysis) Some enzymes also have allosteric sites (for regulation)

allosteric sites bind regulatory molecules: noncovalent, reversible
affects activity of enzyme

positive effectors increase activity
negative effectors decrease activity

How do effector molecules act?

a. change affinity of enzyme for substrate
b. change Vmax

Question 29

control of the number of enzymes mechanisms

speed?

Answer 29

slower than regulation the activity
attenuation
Catabolic pathways: gene induction (by inducer)
Anabolic pathways: gene repression (by corepressor)

Question 30

attenuation

Answer 30

requires attenuator region of the mRNA
attentuator region will form a secondary structure in the presence of certain AA
Lack of AA: will allow secondary structure in attenuator regions to stall ribosome and allow transcription to occur with RNA poly
abundance of AA: attenuator regions do not form secondary structure, leads to the lack of stalling ribo and thus transcription is stopped

Question 31

Catabolic pathways: gene induction

Answer 31

found with pathways that are usually inactive due to a repressor that blocks RNA poly
inducer is produced will bind repressor and induce a allosteric change to prevent the repressor from bonding to the operator region of the DNA and allow transcription to occur = more enzymes

Question 32

Anabolic pathways: gene repression (by corepressor)

Answer 32

seen in genes that are typically active
corepressor will bind to the inactive repressor to form an active repressor that then binds the o region and to repress gene transcription