II Flashcards
stores all the information for the structures and functions of the cell
Dna
genetic information of bacteria is stored in the
chromosome and plasmid
carry genes that recombine with the recipient
mobile genetic elements such as plasmid
Antibiotic resistance gene is acquired through
HGT
linear sequences of DNA that carry coded information for the structure and function of an organism
gene
is typically circular, double stranded chain of nucleotides
chromosome
are extrachromosomal DNA molecules
plasmid
F or
Fertility plasmid
R or
Resistance plasmids
example of plasmids
fertility plasmid, resistance plasmids and virulence plasmids
are extrachromosomal DNA molecules
transposons
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Typically, these other genes are for toxin production or R genes conferring resistance to antibiotics, such as tetracycline, chloramphenicol, or ampicillin. Transposon can move R genes from one plasmid to another or to bacterial genes.
associated from molecules that are required for a bacterium to cause disease
Virulence factor
Cluster of virulence genes. Encode variety of virulence factors such as toxins, superantigens, adhesins, iron uptake systems, secretion systems III and IV, and many effectors that modulate behavior of host cells.
Pathogenicity islands
sequences of DNA that can move both within and between genomes.
MGEs
Horizontal gene transfer typically occurs via
MGEs
examples of MGEs
Plasmids, transposon54s, prophages, insertion sequences
Change in nucleotide sequence of a gene
mutation
Base substitutions or point mutations producing
silent, mis-sense and nonsense mutation
code for the same amino acid
silent mutation
code for a different amino acid
missense mutation
: code for a stop amino acid
nonsense mutation
forms of mutatios observed in bacteria
- Base substitutions or point mutations
- Microinsertions and microdeletions of base pairs
- Reversions
- Deletions of multiple base pairs
- Insertions during recombination
- Translocation
- Inversions
transfer of bacterial genes on their same generation
HGT
Genes encoding resistance to antibiotics, detergents or heavy metals, catabolic enzymes for rare substrates such as citrate, and plant or animal virulence factors may be transferred
by MGEs through HGT mechanisms.
requires direct contact through the conjugative (sex) plasmid of the donor and recipient cells
It transfers much larger quantities of DNA (occasionally whole chromosomes).
DNA acquired either the original bacterial chromosome or plasmid in a previously infected bacterial cell is incorporated into bacteriophage nuclei acid and transferred by progeny of the phage to susceptible recipient cells.
viruses that infect bacteria.
only genes near the attachment site of the phage on the chromosome of host cell are involved
Specialized transduction
2 forms of transduction
Generalized
Specialized
virtually any gene (genetic marker) of the host bacterium can be transferred
Generalized transduction
Involves the transfer of free or naked DNA containing genes on a segment of chromosomal or plasmid DNA from a lysed donor bacterium to a competent recipient
Transformation
ability of the bacterium to take up free DNA
Competence
released into the medium from the recipient which facilitates the entry of DNA
Competence factor
T or F. Not all bacteria can be transformed because some could not become competent.
True
Virulence factor of Bacillus antracis
Capsule, toxins/ plasmid
Virulence factor of Clostridium botulinum
Neurotoxins/bacteriophages
E. coli
Shiga-like toxin/bacteriophage adherence factor
Enterotoxins/plasmids
Heat-stable toxin, siderophore production/transposons
Virulence factor of Salmonella Dublin
Serum resistance factor/plasmid
Virulence factor of Staphylococcus aureus
Enterotoxins (A,D,E),toxic shock syndrome factor I/ bacteriophages
Coagulase,exfoliatin toxin, enterotoxins/ plasmids
Virulence factor of Yersinia pestis
Coagulase, fibrinolysin/ plasmid
usually affects bacterial ribosomes
-mutation alters DNA such that the protein produced or target is modified. The antimicrobial agent can no longer bind to target
Alteration of targets
Example of alteration of target
resistance to erythromycin, rifamycin, and antimetabolites has developed by this mechanism
Mechanisms of antibiotic resistance
- Alteration of target
- Alteration of membrane permeability
- Development of enzymes
- Alteration of enzymes
- Alteration of metabolic pathways
- Elimination of antibiotics through membrane-bound efflux pumps
