Bacterial genetics and exchange of genetic information

Vertical transmission

from parent to daughter cells

Horizontal transmission

between unrelated bacteria

Are bacteria haploid or diploid

haploid

Silent mutations

no change in the main acid sequence

Missense mutations

one base substitution—→ one amino acid change

nonsense mutations

early termination of the peptide chain

Transposons

Segments of DNA that move from one site on a DNA molecule to another, Can create mutations when they move (on the ends of cut DNA). Can include genes for antibiotic resistance. Can jump between chromosomes and plasmids (and vice versa).

Bacteria can share genes for:

-Enzymes: cleavage of antibiotics

-Membrane proteins: for efflux of antibiotics

-Also exotoxins and adhesive factors (pili)

Unidirectional gene transfer

donor to recipient (not swapping genes), does not donate the entire chromosome

Transformation

-relatively rare form of genetic transfer

-DNA must be integrated into the host chromosome

-Linear DNA is broken down quickly by the bacteria

-The new DNA must be integrated into the genome

Two steps required for transformation

1. Uptake of DNA from the environment

2. recombine or insert new DNA into the chromosome

Conjugation

-gene transfer from a donor to a recipient to by direct physical contact between cells

-donor bacteria forma sex pilus to pull bacteria close together (transfer plasmid)

Conjugation Steps

-F-factor: plasmid from the donor bacteria that includes the genes for the sex pilus

-Donor transfers plasmid to recipient bacteria. New DNA may be degraded and fragments inserted into the genome or maintained as a plasmid.

-Recipient is now able to pass the plasmid onto other bacteria.

Transduction

Transfer of genetic information by bacteriophages.

Generalized transduction

Phage carries just bacterial DNA

Specialized transduction

Phage carries some bacterial and some viral DNA

Is stephylococcus aureus Gm+ or Gm-

GM+

MSSA and MRSA

Acquired a gene (PBP2a) which encodes for a transpeptidase that does not bind to the penicillin. Often treated with vancomycin

what types of genes are increasily common in E.coli and Klebsiella pneumonia

NDM1 and ESBL