Bacterial Metabolism and Genetics Chapter 13 PDF

Bacterial Metabolism and Genetics Chapter 13 p. 132-136 Gene Exchange in Prokaryotic Cells Many pathogenic bacterial species are “promiscuous” with their DNA – exchange of DNA between cells allows the exchange of genes...

Bacterial Metabolism and Genetics Chapter 13 p. 132-136 Gene Exchange in Prokaryotic Cells Many pathogenic bacterial species are “promiscuous” with their DNA – exchange of DNA between cells allows the exchange of genes and characteristic of cells, thus producing _______________ _________________ bacteria new strains of a roulatDNz – may be advantageous for the recipient antibiotic resistance small , – can be integrated into recipient chromosome or stably ↑ maintained as an extrachromosomal element (plasmid) or bacterial virus (bacteriophage) and passed on to daughter cells 1  Gene Exchange in Prokaryotic Cells Plasmids * – small genetic elements that replicate independently of the chromosome "extrachromosomal" – most are circular, double stranded, 1500-400,000 bp – genetic information usually not essential but provides a selective advantage antibiotic resistance 8 bacteriocins give virulence bacteriocins factors toxins advantage over – replicate autonomously – replicons other invaders- – some can integrate into the host chromosome - _____________ episomes Infects other bacteria with toxins Gene Exchange in Prokaryotic Cells virus thaiteral infects Bacteriophages (phages) – bacterial viruses with DNA or RNA genome protected by a Bacteriophages protein shell * – infect bacterial cells __________– lytic cycle replicate in large ~ numbers causing the cell to lyse kills __________– integrate into the ~ lysogeniccucle host genome without killing the not host doesWill 2  label and to draw Beable C this * Lytic and Lysogenic Cycles here go can ! Phages oversaturate to In host cell , leading be replicated allows Viral and to lytic event, allowingother wout Wibacterial chromosomes phages to propagate cell. But exposure to killing the host and bacterial cells certain things induces excision the phage + bacterial cell may allow to undergo lytic cycle Gene Exchange in Prokaryotic Cells Transposons (jumping genes) – mobile genetic elements that can transfer DNA within a cell, from one position to another in the genome, or between different molecules of DNA (e.g., plasmid to plasmid or plasmid to chromosome) – _____________________ Insertion Sequence simplest - inverted repeats and transposase (with no other genes this, is fine. But if genes for – _____________________ complex antibiotic resistance of toxins , creates big problem) genes for transposition and other genes – antibiotic resistance – toxins 3  Gene Exchange in Prokaryotic Cells simpleposals complex ente 4  Gene Exchange in Prokaryotic Cells Pathogenicity or virulence island · – segments of genes that contribute to pathogenicity of bacteria bounded at Salmonella typhimurium each end by transposon-like mobile elements can move within the chromosome and to other bacteria can be triggered by an environmental stimulus – SPI-1 of Salmonella spp.* 25 genes allowing the bacteria to enter uni cells _______________________ Type Ill Secretion system i s (T3SS) cytoskeletal rearrangement plasmid - chromosome Mechanisms of Genetic Transfer between Cells Vertical-Mom-baby Horizontal-neighbor-neighbor Horizontal/lateral gene transfer I Conjugation Transduction Transformation to Need know ⑨ Prophage da pilasering type cantransfer/propagate or lysed cells might - release phages into enkronment for cells to take in 5  Mechanisms of Genetic Transfer between Cells S procesd First covere - dis _____________________ Transformation – process by which bacteria take up mid partfragments of naked DNA and incorporate them into their genomes - > Alive – Gram + and Gram – bacteria can take up and stably maintain exogenous DNA O -dead certain species are naturally capable of taking up exogenous DNA – "Competent ________________ " F & – Haemophilus influenzae, Streptococcus pneumoniae, Bacillus spp., Neisseria spp. competence can be induced* Idone all time major tool - maxi/min i prep the , in DNA replication) * DNA found to be the hereditary Transformation Material dead s cells , * Francis Griffith exp - - R cells living. * S smooth R = = Recovers smooth , cells This means rough. genes required for Ismooth has capsule = smooth capsule were virvience factor , fatal picked up by living 12 cells * Rcells do not have to genes required thus produce capsule , virulent Transformationa It not > - 6  a on Mechanisms of Genetic Transfer between Cells Conjugation ___________________ ↓ 59 I-V be – one way transfer of DNA from a donor (male) cell to a recipient -type to (female) cell through a sex pilus Episomal wherintegrated : – occurs with most bacteria, usually Y is between members of the same or Fplasmidcell entire the related species +. into Hos can then be – mating type depends on the genome presence (male) or absence trans ferred (female) of a conjugative plasmid F plasmid _________________ Conjug F ema – carries all the genes necessary of & its own transfer conuator copy d "fertilityac plasmi " » ability to make sex pilus (type IV secretion system) » initiate DNA synthesis Mechanisms of Genetic Transfer between Cells Transduction – mediated by bacterial viruses (phages) specialized ________________ – the phage transfers particular near Prophage genes (usually those adjacent to DNA Host integration dia some neattheir integration site in the + notpost sith to by host and genome) ________________ Generalized – incorporation of DNA is random because of accidental packaging of host DNA into the phage capsid mix of prophage + host chromosomal dna 7  Transduction Some lysogenic phages carry toxin genes – corynephage beta carries the gene for the diphtheria toxin Corynebacterium diphtheriae - Pseudomembranes c deuFoxin “Bull neck” massive swelling In airman o , asphixuation Generation of Vancomycin-Resistant S. aureus by Multiple Genetic Manipulations · MRSA – resistant to b-lactams & 1997 Japan – first clinical isolate of S. aureus with decreased susceptibility to ↳ vancomycin – MIC = 8 µg/mL – additional strains isolated in several countries including US ↓ VISA (MIC ≤ 16 µg/mL) June 2002 US – high level vancomycin resistant S. aureus (MIC = 1024 µg/mL)* Increasing Mic , from a dialysis patient in Michigan thickening cell wall of the ↑ Mother land Every resistant strain First strain of MUSA 8  Generation of Vancomycin-Resistant S. aureus by Multiple Genetic Manipulations minimmd o Generation of Vancomycin-Resistant S. aureus by Multiple Genetic Manipulations Patient Diabetic foot ulcer with – 40 year old woman gangrenous digit hypertension A diabetes mellitus Big - peripheral vascular disease chronic renal failure factor ! to – hemodialysis * recurrent foot ulcers Without blood flow to the area cannot heal , Chang et al. (2003) N Engl J Med 348:14 9  Generation of Vancomycin-Resistant S. aureus by Multiple Genetic Manipulations Hospitalization puts for you at high risk nosocomial infections MUSA , * urst microbiome vancomyo at some point , there was Confection biw MusA and URE, which led to horizontal gene Chang et al. (2003) N Engl J Med 348:14 transfer musa + I Osin use Generation of Vancomycin-Resistant S. prolonged vancomy led to VRE promotion , aureus by Multiple Genetic Manipulations = VRSA MRA C Re F no. runco ng * D labetes ger the eso a lactorialize 70 & d MrsA picked up plasmid either transformation or Conjugation. via corde a -Genes for resistance were on transposable vancomyos Extended element 10 - Conjugation for other cells via mutated progeny  Generation of Vancomycin-Resistant S. aureus by Multiple Genetic Manipulations 1. MW marker laymentst t o 2. VRE plasmids 3. MRSA plasmid 4. VRSA plasmid Te lane 3 and 4 are identical except for 7. 0 probe , the gene found VRSA to lane 4 in jumps n or Weigel et al. (2003) Science 302 D-Ala 11