Microbiology Test 1 Flashcards

desiccation, starvation, cell density

-->sigmaF is released -->activates sigmaE -->signal from mother cell triggers sigmaG in endospore and sigmaK in mother

sigma factors

Sequences at the end of the gene trigger release of the polymerase and the completed RNA molecule

The sequential addition of ribonucleotide from nucleoside triphosphate to the 3’OH end of the growing chain

Bind of the RNAP to the beginning of the gene, followed by opening the DNA helix and start of RNA synthesis

Transcription (DNA to RNA) is carried out by RNA polymerase.

• RNA polymerase uses DNA as template.

• RNA precursors are ATP, GTP, CTP, and UTP.

• chain growth 5′ to 3′, just as in DNA replication

• only one strand transcribed
• no priming needed

The 23S rRNA catalyzes peptide bond formation in the growing polypeptide chain.

used for folded proteins

• Signal sequence RRXFXK • TAT System
• Powered by Proton Motive Force (PMF)

Sec dependent

protein wraps around SecB--> goes over to SecA and SecYEG(embedded in membrane) -->protein is pushed through SecYEG with help from SecA and ATP and goes into periplasm -->LepB cleaves the signal sequence -->protein is folded in periplasm

Signal Recognition Particle

Transport to membrane: Protein is synthesized & localized

Protein is unfolded

clusters of ribosome bound to an mRNA

• Stop codon (UAA, UGA, UAG)
• release factor (either RF 1 or RF 2) enters A site, no tRNA for stop codons
• Peptidyltransferase is activated and releases the completed protein from tRNA in the P site
• Ribosome recycling factor (RRF) & EF-G undocks 50S from 30S
• IF3 removes uncharged tRNA & mRNA

• EF-Tu-GTP binds tRNA, binds A site, GTP hydrolysis
• Peptidyltranferase makes peptide bond
• EF-G-GTP, hydrolysis of GTP, tRNA moves to P site

Specific factors:

-E.coli- IF1, IF2 & IF3
-M. jannaschii- 6 IF proteins

allows coordinated expression of multiple related genes in prokaryotes.

function to transfer the correct amino acids to the ribosome during translation.

(5'-AGGAGGU-3')

Initiation is at any Shine– Dalgarno sequence; the mRNA can therefore be a polycistronic mRNA that codes for several polypeptides.

An operon is a cluster of genes that are under the control of a single promoter and are therefore cotranscribed as a single, polycistronic mRNA molecule. This arrangement allows related genes to be expressed in a coordinated fashion

Ribosomal binding site-Start codon-coding sequence-stop codon

amino acid synthesis

transcriptional activity exclusively

phosphorylation

none of these

negative / inducer

leading

leading

distribution of genetic material in replicating Caulobacter.

Promotes growth of stalk, cell elongation and division

• GcrA levels rise and promotes elongation phase of chromosome replication, cell division & growth of the the stalk on immobile daughter cell
• GcrA levels fall, and high levels of CtrA reappear in the daughter cell

Transcriptional regulator for flagellar synthesis; represses GcrA expression & DNA replication

• CtrA is activated by phosphorylation • CtrA~P activates genes need for flagella & represses synthesis of GcrA & • CtrA~P inhibits the initiation of DNA replication by binding the origin.
• CtrA gets degraded by a specific protease resulting in increasing DnaA levels
• Absence of CtrA allows for DNA replication to initiate • DnaA is then also degraded by a protease

• Gram-negative
• α-proteobacteria
• Aquatic bacterium with differential life styles – Swarmer – Stalked/attached
• Good to study cell cycle in

crescentin and MreB

1. Phenotypic changes often occur without a genotypic change when an organism is placed in a different environment. This could be due either to changes in gene expression or abiotic (physical or chemical) factors that alter a gene product.

1. Phenotypic changes do not always accompany genotypic changes. Genotypic changes that do not alter the phenotype could be due to point mutations that do not result in changes to the primary structure (amino acid sequence) of a protein (i.e., silent mutations)

• The observable characteristics of an organism based on its genetic composition.

1. The complete genetic makeup of an organism. Its precise determination would require genomic sequencing

-Proofreading (make sure A & T together and C & G together)

-Thiamine dimer (detects damaged bases -->cuts nucleotides-->replaces nucleotides that were cut-->nucleotide linkage)

FtsZ

origin of replication

1,000

RNA

3

2

nucleotide

binds terminus and blocks progress of the replication fork

ligA, ligB

seals nicks in DNA

polA

excises RNA primer and fills in gaps

proofreading subunit

polymerase subunit

strand elongation

dnaX

holds together the 2 core enzymes for the leading and lagging strands

clamp loader

loads Poly III onto sliding clamp

an enzymes ability to catalyze consecutive reactions w/o releasing its substrate

sliding clamp (beta clamp)

holds Poly III on DNA

involved in processivity; processivity factor for DNA polymerase

binds DNA polymerase III and prevents dislocation

3' to 5'

main polymerizing enzyme; the main replication polymerase

subunit for proofreading (dnaQ)

Primase

priming; primes new strands of DNA

RNA primer synthesis

rifampin resistant RNA polymerase

single-strand binding protein

cover and protect the unreplicated single strand

helicase

unwinds double helix at replication fork

prepriming

DNA-dependent rNTPase

helicase loader; loads helicase at origin

open the DNA helicase protein ring and place the ring around the single-stranded DNA at the origin. Loading of the DNA helicase leads to the release of the helicase loader

origin binding protein; binds oriC

binds origin of replication to open double helix

initiation

dnaB loading

binding of dnaA leads to the strand separation at the 13-mer repeats

gyrAB gene

replaces supercoils ahead of replisome

10

1 ring

thymine and cytosine

2 rings

Adenine and Guanine

required for correct placement of division site