Bacterial Metabolism and Genetics Flashcards
Nutrients required by bacteria
CHONPS and trace metal salts
What versions of C and N are most important?
Reduced Form
Describe the shape of a bacterial growth curve based on temperature.
The curve leans with the highest point/optimum at higher temperatures
What is the significance of the bacterial growth curve?
Increase in temperature by as little as 2 degrees causes a large drop in population – FEVER
Three types of bacteria based on pH? Who is most common in the stomach? The body?
Acidophile, Neutralophile, Alkalophile
Acidophile
Neutralophile
Circumstances in which an aerobe will grow?
O2
Needs an electron acceptor – O,N,S
Circumstances in which an anaerobe will grow?
Grows in No O2
O2 forms radicals
Circumstances in which facultative anaerobes grow?
Grows in O2, less well without O2
Have TCA and can ferm.
Circumstances in which aerotolerant will grow?
Will grow with or without O2
Doesn’t use O2 anyway
Circumstances in which microaerophile will grow?
Grows in O2 below 0.2 ATM
Needs O2, but too much makes radicals
Oxygen sensitivity of more tissue?
Anerobic
Oxygen sensitivity of lungs?
Aerobic
Oxygen sensitivity of tonsils/back of throat?
Microaerophile
Four phases of bacterial growth cycle?
Lag, Exponential, Stationary, Decline
What stage are bacteria typically in the lab? In the body?
Exponential Phase.
Stationary Phase.
What occurs during the lag phase?
Adaption to new nutrients
New enzyme synthesis/up-regulation
What occurs in the exponential phase?
Growth and binary division
What occurs in the stationary phase?
Crowding, Starvation or Toxic Conditions
Stress Genes Upregulated
What occurs in the decline phase?
Cells begin to lyse.
What occurs in bacterial latency?
No division, allows for hiding from immune response
“Persister cell”
How do persister cells come about?
Turn off metabolism
Turn on dormancy pathways
No growing/dividing
Role of persister cells in treatment?
Treating against persister cells leads to more rapid cure
Describe the bacterial chromosome.
Circular
Stable w/out telomeres
Haploid (typically)
Associated with proteins (structural and regulatory)
What are merodiploids?
Genes in multicopy in the bacterial chromosome
Describe a plasmid?
Circular, smaller than chromosome
Can exist in hundreds of copies per cell
What controls plasmid replication?
Cop proteins
In a broad sense, how does bacterial transcriptional regulation occur?
Negative Regulation – Protein Repressors
Positive Regulation – Protein Activators
Where do repressors bind?
Between promoter and gene
Where do activators bind?
Upstream of promoters
How do environmental signals modify gene regulation?
Small molecules alter the shape/bind to regulatory proteins
Two types of environmental signals?
Induction and Repression
What are two ways in which repression may work?
Trigger Active Repressors
Inactivate Inducer
How does the lactose influence the lac operon?
Lactose present inhibits the lac repressor protein
How does high glucose influence the lac operon?
High glucose will lead to low cAMP
With low cAMP, minimal binding of Lac Inducer
Transcription at low rate
How does low glucose influence the lac operon?
Low glucose leads to higher cAMP levels
cAMP+CAP activator binds, induces great amount of lactase transcription
What happens in bacterial transformation?
Uptake of unpackaged DNA
What triggers bacterial transformation?
Competence pharomones/Quoromones are secreted as nutrients run out
Quorum Sensing
How might DNA transformation be induced?
High temperature opens membrane pores
CaCl2 shields DNA- charges and lets new DNA in
How might one make bacteria transformation occur in a laboratory setting?
Gene gun, electroporation
What is conjugation?
Natural Plasmid Transfer
How does conjugation occur?
Cells with F+ plasmid generate sex pili that binds to receptors on F- pili
What are Hfr cells?
Cells that in conjugation can transfer chromosomal genes
How are chromosomal genes transferred with plasmids?
Following integration of F plasmid, adjacent chromosomes be come with the F plasmid with abnormal excision
P’ Plasmid
Significance to chromosomal gene transfer in plasmids?
Can generate R-plasmids
Resistance genes pulled along with the plasmid
What is transduction?
gene transfer mediated by imprecise excision or packaging of phage
Difference between generalized and specialized transduction?
Generalized – lytic phage – could be any gene
Specialized – lysogenic phage – only genes near integration site
What happens in bacterial gene replacement?
transferring genes integrate into host chromosome replacing native genes
Homologous recombination is catalyzed by ____. What unique thing may happen to the DNA?
RecA
Inversions
Where do inversions happen? Where do deletions occur?
Inversions – Between Inverted Repeats
Deletions – Between Direct Repeats
How does recombination at dissimilar sequences occur?
transposons acting via transposases
Difference between composite and non-composite transposons?
Non – inverted repeats at end and transposase
Comp – Complete IS elements at ends, genes in middle
Two pieces of medical significance of plasmids
Antiobiotic resistance transfer
Interruption of genes resulting in mutation
What are outer membrane vesicles?
Small vesicles that bud from outer membrane containing genetic elements and signalling molecules
Why do we care about outer membrane vesicles?
Blebbing and budding with genes/proteins/virulence factors provides extra routes of transmission
