microbial physiology and metabolism Flashcards
Elements required for cell components
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
Sources of Energy
Phototrophs-Light
Chemotrophs-oxidation of organic or inorganic compounds
Sources of Reducing Equivalents
why are these needed?
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
Sources of Carbon/ methods of getting it
Autotrophs- CO2 main/only source
Heterotrophs- reduced, preformed organic molecules
Major Nutritional Types of pathogens
Chemoorganotrophic heterotrophy
chemical energy source
organic electron donor
organic carbon source
N source
amino acids, ammonia nitrate > ammoniaN2
P source
Pi
S source
sulfate (SO42-) reduced sulfur (e.g. cysteine)
Growth factors sources
amino acids
purines and pyrimidines
vitamins (small organic molecules)
Bacterial oxygen responses
strict anaerobes/aerobes
facualtive anaerobes
strict aerobes
perform aerobic respiration only
final electron acceptor is oxygen (reduced to H2O)
strict anaerobes
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)
facultative anaerobes
can perform respiration if O2 is present and fermentation if it is absent
most medically relevant bacteria
the respiratory chain of E. coli
two chains that can be used in high (cyto o) and low (cyto d) oxygen
Nutrient uptake methods
facilitated dif
group translocation/ active transport
Facilitated diffusion
driven by?
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
Group translocation
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
Active transport, types found?
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
ion-driven transport systems, limited?
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
Binding protein-dependent transport systems
mechanism and common substances?
saturation?
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
Iron Uptake
- 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
Nutritionally fastidious, examples?
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
obligate intracellular parasites
require intracellular host
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?
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
Mechanisms of adaptation
- Maximize efficiency in using energy and resources
* Respond to changes
The result of regulation:
pathways can be switched on and off
pathways can be turned up or turned down
How is control established?
- Control of enzyme activity
2. Control of the number of enzyme molecules
Allosteric regulation of enzymes
what do these modify?
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
control of the number of enzymes mechanisms
speed?
slower than regulation the activity
attenuation
Catabolic pathways: gene induction (by inducer)
Anabolic pathways: gene repression (by corepressor)
attenuation
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
Catabolic pathways: gene induction
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
Anabolic pathways: gene repression (by corepressor)
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
