Bacterial Genetics Lecture Notes (PDF)

CLINICAL BACTERIOLOGY — Lecture 1st SEM | PRELIMS Joanne Krystine G. Tago Bacterial Genetics...

CLINICAL BACTERIOLOGY — Lecture 1st SEM | PRELIMS Joanne Krystine G. Tago Bacterial Genetics – Transformation Occurs after the uptake of DNA fragments from the The Chromosome environment – single, long pierce of circular, double-stranded DNA When a bacteria dies, it breaks into pieces and the – contain 2000 to 4000 genes genetic material is fee in the environment – contains all the information needed for cell growth and Occur only to competent bacteria replication ○ Able to accept naked DNA from the environment Plasmids-> ability to produce sex pilms ○ Streptococcus pneumoniae, Neisseria – small DNA circles gonorrhoeae, and Haemophilus influenzae, – replicate independently do this naturally – genes for toxins, proteins that promote transfer If the DNA is a circular plasmid and the recipient cell – not essential for bacterial growth, so they can be gained or is compatible, the plasmid can replicate in the lost cytoplasm and be transferred to daughter cells – number of plasmids present in a bacterial cell may range during cell division from one (low copy number) to hundreds (high copy RecA protein number) ○ a recombinase functioning in a — may sometimes be passed (nonsexually) from one recombinational DNA repair in bacteria bacterial species to another ○ Critical enzyme which catalyzes the pairing of the single stranded DNA with a complementary regions of the double Vertical Gene Transfer stranded DNA – mother to cell offspring – binary fission Horizontal Gene Transfer – Conjugation transfer of genetic material from a donor bacterial strain to a recipient strain Example: – Transduction ○ In the E. coli system, the donor strain (F+) Transfer of DNA fragments from one bacterium to possesses a fertility factor (F factor) on a another by bacteriophage plasmid that carries the genes for Bacteriophage are viruses conjugative transfer ○ Bacteriophage consists of a chromosome Donor strain produces a hollow surface appendage (DNA or RNA) surrounded by a protein coat called a sex or conjugation pilus Types of Bacteriophage: F+ conjugation - ○ Lytic or Virulent phage (T phages) ⑭ > passing ○ Bacterial mating of plasmid that Replicates usually through Lytic male codes for sex pilus ○ Enteric, gram (-) bacteria Cycle Resistance plasmid conjugation Production of viruses using a host ○ R plasmid is being shared cell to manufacture more viruses ○ R plasmid = some form of antibiotic Would cause the host bacteria to die resistance so new variants will come out of host cell Bacteriophage DNA directs the bacterial cell to synthesize phage DNA and phage protein and package it into new phage particles bacterial cell eventually lyses (lytic phase) releasing a new phage that can infect other bacterial cells ○ Temperate phage (phage lambda) Replication through Lysogenic Cycle Incorporation of the viral genome into the host cell genome creating Prophage ! DNA with a strand angelr_m BSMLS 3H brought by bacteriophage  jumping geres ↑ Does not kill the host cell – Transposons — mobile DNA segments immediately May cause plasmids to integrate into chromosome Variance will contain the prophage Responsible for the spread of antibiotic genes (temperate phage + bacterial host) Related mobile elements that contain additional Genes present in the phage DNA genes may be expressed by the bacterial Often carry drug-resistance genes and are usually cell located in plasmids – When the lytic phages replicate the capsid sometimes assembles around a small fragment of the bacteria DNA – Bacteriophage but carries the bacterial DNA virus that carries bacterial DNA – Lysogenic Conversion Cells are immune to reinfxn by same phage Cells may exhibit new properties Allows phage to take a bit of the adjacent bacterial DNA Initiated by the temperate phage which undergoes the lysogenic cycle as it replicates Transfers genetic material to another bacterial host, it does not just carry viral DNA but also carries the bacterial DNA Example: ○ Corynebacterium diphtheriae ○ Streptococcus pyogenes ○ Clostridium botulinum ○ Vibrio cholerae Mutation – any change in the DNA base sequence – changes that occur in the DNA code and often result in a change in the coded protein – mutation may be the result of a change in one nucleotide base – also occur as the result of error during DNA replication at a rate of about 1 in 107 cells – exposure to certain chemical and physical agents can greatly increase the mutation rate Mobile Genetic elements – certain pieces of DNA are mobile and may jump from one place in the chromosome to another place – sometimes referred to as jumping genes angelr_m BSMLS 3H