Micro Exam #3 Review

covalent modification

irreversible (proteolysis) or reversible (de/methylation or de/phosphorylation)

MCPs

chemoreceptors in membrane that bind environmental chemicals and initiate a series of interactions with cytoplasmic proteins that affect flagellar rotation

MCPs

activate sensor kinase CheA

CheA

sensor kinase that autophosphorylates and phophorylates the response regulator CheY

CheW

helps CheA autophosphorylate

CheY

response regulator, governs flagella rotation

CheY

when active diffuses to flagellar motor and switches

CheR

MCP is methylated

CheB

MCP is not methylated

CheY

when inactive, flagellar rotation is counter clockwise and running occurs

regulatory system

allows E. coli to respond to and adapt to very small amounts of attractant

quorom sensing

cell to cell communication mediated by small signaling molecules such as AHL, usually from the same species, can be used as a offensive weapon in crowded environments

LuxR

transcriptional regulator, stimulates transcription of the genes for AHL synthesis and proteins needed for light production

stringent response

occurs when bacterial cells are starved for amino acids and protein synthesis cannot proceed, cell decreases production of tRNA and rRNA to conserve E and decreases biosynthesis of AAs

RelA

downregulates synthesis through production of pppGpp

pppGpp

works with DksA to destabilize transition initiation open complexes

sporulation

global reg system in which phosphorelay, posttranslational modification of proteins, transcription initiation reg proteins and alternative sigma factors play a role

starvation signal

induces production of alternative sigma factor

conjugation

recombination complimentation that results in chromosomal extrachromosomal loss through plasmids

transformation

recombination complimentation that results in chromosomal extrachromosomal loss through the environment

transduction

recombination complimentation that results in chromosomal extrachromosomal loss through phages

advantage/disadvantages to DNA transmission

* response to stresses and host threats
* evasion of host immune system
* adaptation to diverse environments
* enables drug resistance

plasmids and transposable elements

mobile genetic elements

signaling cascade

begins the cell replication process

cell enlarges, DNA replication begins

step of cell replication that occurs directly after the signalling cascade

PM and cell wall invagination

occurs after and sometimes during replication

chromos move to opposite ends of cell

step of replication that occurs after PM and cell wall invagination

septum

runs through the center of the cell after DNA replication

septum

forms after PM and cell wall invagination and before cell division

daughter cells divide

occurs after the septum forms

binary fission

how most bacterial cells divide

DNA replication & cytokinesis

2 pathways functioning during the cell cycle

DNA replication and partition

how a cell inherits plasmids during division

cytokinesis

cytoplasm divides before daughter cells seperate

origin of replication

site at which replication begins

terminus

site at which replication is terminated, located opposite of the origin

replisome

group of proteins needed for DNA synthesis

both directions

directions that DNA replication proceeds from the origin during replication

origins

move to opposite ends of cell during replication

septum formation

begins when the Z ring forms

partitioning

occurs when the replisome pushes, or leads to condensation of, daughter chromos to opposite ends of the cell

ParA

polymerizes to form filaments, causes ParB/parS complex to depolymerize and pulls one copy of DNA away

ParB

binds DNA at parS site near the origin of replication (technically binds 2 copies of parS site since DNA has been replicated)

70%

% of sequenced bacterial genomes that experience chromosome partitioning

cytokinesis

process that results in 2 daughter cells

septation

formation of cross walls between daughter cells

cytokinesis steps

selection of site for septum formation → assembly of Z ring & cell wall synth machinery → constriction of cell and septum formation

Z ring formation

required for septation

Z ring

forms as FtsZ proteins polymerize to form filaments

FtsZ

proteins that create meshwork that becomes the Z ring

Z ring

marks the proper place for septation

ParA & ParB

proteins that ensure that the chromos have moved to the correct place before allowing for the Z ring to form

divisome

finishes division after the formation of the Z ring

FtsZ

forms Z ring

FtsA & ZipA

anchor Z ring to the PM

Ftsl & FtsW

divisome proteins involved in peptidoglycan synthesis

divisome formation

anchoring proteins link Z ring to the PM→ cell wall synth machinery assembled → constriction of Z ring, invagination of the PM and synth of septal wall completing division

cell shape

determined by peptidoglycan synthesis in bacteria

PBPs

link peptidoglycan strands and catalyze controlled degradation for new growth

autolysins

PBP enzymes that degrade peptidoglycan at site where new units are added

UDP binds to NAG or NAM

occurs in the cytoplasm, step that begins peptidoglycan synthesis

NAM

transferred from UDP to bactoprenol at the plasma membrane before being transported out of the cytoplasm

bactoprenol

receives NAM from UDP at the PM, flips NAG & NAM complex from the cytoplasm to the outside

autolysins

aid in attaching the NAG & NAM together to the growing peptidoglycan in the perioplasmic

cell growth

varies based on cell shape

cocci divisome

new peptidoglycan forms only at septum → FtsZ detmines the site of cell wall growth → FtsZ may recruit PBPs for septum synthesis

rods

elongate prior to sepatation → MreB determines cell diameter/elongation as Z ring forms

MreB

in rods,determines cell diameter/elongation as the Z ring forms

vibrio

comma shaped bacteria

vibrio cell wall growth

FtsZ forms Z ring → MreB = helical polmerization throughout the cell → crescentin = IF homologue localizes to short curved side of cell → asymmetric cell wall synthesis

MreB

responsible for helical polymerization throughout the cell

crescentin

intermediate filament homologues

extremophiles

grow under harsh conditions that would kill most other organisms

hypotonic solution

lower osmotic concentration → water enters the cell → cell swells and may burst

hypertonic

higher osmotic concentration → water leaves the cell → membrane shrinkage from cell wall (plasmolysis) may occur

adaptation to osmotic changes

* hypotonic → mechanosensitive (MS) channels in PM allows solutes to leave
* hypertonic → increase solute concentration with compatible solutes to increase to increase osmotic concentration

halophiles

grow optimally in the presence of NaCl or other salts at a concentration above about 0.2M

extreme halophiles

require salt concentrations of 2M and 6.2M, extremely high concentrations of K+, cell wall, proteins, and PM require high salt to maintain stability and activity

pH

measure the relative acidity of a solution

acidophiles

growth optimum btwn pH 0-5.5

neutrophiles

growth optimum btwn pH 5.5-

alkaliphiles

growth optimum btwn pH 8.5-11.5

neutrality

level that most microorgs maintain internal pH

microbe adaptation to pH

* PM impermeable to H+ & exchange K+ for H+


* Acidic tolerance → pump out H+
* synth acid and heat shock proteins that protect proteins
* change pH of habitat by producing acidic or basic waste products

cardinal growth

how orgs exhibit growth temperatures

high temperatures

may inhibit enzyme functioning and be lethal

enzymes

have optimal temperature at which they function optimally

psychrophiles

optimal growth between 0-20 degrees C

psychrotolerant

optimal growth between 0-35 degrees C

mesophiles

optimal growth between 20-45 degrees C

thermophiles

optimal growth between 55-85 degrees C

hyperthermophiles

optimal growth between 85-113 degrees C

adaptation of thermophiles

* protein structure stabilized by more H+ bonds, more proline chaperones
* DNA stabilized by histone-like proteins
* membrane stabilized by more saturated, branched, higher MW lipids and ether linkages

aerobe

grows in presence of atmospheric O2, which is 20%

obligate aerobe

requires O2

anaerobe

grows in the absence of O2

microaerophile

requires 2-10% O2

facultative anaerobes

do not require O2, but grow better in its presence

aeotolerant anaerobes

grow with or without O2

SOD

superoxide dismutase which breaks down O2 radicals