Individual E. coli strains contain only a subset ofthe E.colipangenomeCore genome: Genes shared by all bacterial strains of a givenspecies.~1000genesforE.coliPangenome:The core genome of a bacterial species plus allgenes found in some strains but not others.~15,000genesforE.coliUnique phage regiorGenestranscribecfromdifferentDNAstrands(inoppositedirections)E.coli pangenome-15,00ogenesCoreAverageE.coligenomegenome has~1000_4700genesgenes3.0GenepresentFig.13.6,Geneabsent2.0Genedivergent13.7Genomic island15-11fromShigefla
Copyright © The McGraw-Hill Companies, Inc. Permission required to reproduce or display 15-11 Individual Individual E. coli E. coli strains contain only a subset of strains contain only a subset of the E. coli E. coli pangenome pangenome Core genome: Genes shared by all bacterial strains of a given species. ~ 1000 genes for ~ 1000 genes for E. coli E. coli. Pangenome: The core genome of a bacterial species plus all genes found in some strains but not others. ~ 15,000 genes for ~ 15,000 genes for E. coli E. coli. Fig. 13.6, 13.7
(a)lSelementstructureBacterialgenomesISelementcontain transposableelementsInvertedrepeats(b)IS insertion into lacZ geneTransposable elementsDirection of transcriptionplace DNA sequencesat various locations inlacztthe genomeMany of the、一ISspontaneous mutationsInlacz-isinterrupts laczgeneandpreventsin E. coli result from IStranscriptionoftheentiregene.transposition into a(c) Tn10 structuregene.TransposonTn10IS10LIS10RGenefortetracyclineresistanceFig.13.815-12
Copyright © The McGraw-Hill Companies, Inc. Permission required to reproduce or display 15-12 Bacterial genomes contain transposable elements Transposable elements place DNA sequences at various locations in the genome. Many of the spontaneous mutations in E. coli result from IS transposition into a gene. Fig. 13.8
Plasmids carry additional DNABacteriumPlasmids: Small circles of double-stranded DNA that can replicate inObacterial cellsindependently oftheBacterialPiasmidchromosome.chromosomePlasmids vary in size ranging from1kb-3Mb.Plasmids are not neededforreproduction or normal growth, butthey can be beneficial.15-13Fig.13.9
Copyright © The McGraw-Hill Companies, Inc. Permission required to reproduce or display 15-13 Plasmids carry additional DNA Plasmids vary in size ranging from 1 kb – 3 Mb. Plasmids are not needed for reproduction or normal growth, but they can be beneficial. Fig. 13.9 Plasmids: Small circles of doublestranded DNA that can replicate in bacterial cells independently of the chromosome
Some plasmids contain multiple antibiotic resistance genesPlasmids can carry genes that confer resistance to antibioticsand toxic substances.Plasmids can transfer genes from one bacteria to anotherTn5+Tn3+SmIS1KanIS1AmpYocmTn4Resistance-determinant0segmentSFig 13.1015-14
Copyright © The McGraw-Hill Companies, Inc. Permission required to reproduce or display 15-14 Some plasmids contain multiple antibiotic resistance genes Some plasmids contain multiple antibiotic resistance genes Fig 13.10 Plasmids can carry genes that confer resistance to antibiotics and toxic substances. Plasmids can transfer genes from one bacteria to another
SomeR plasmids carrybla(Amp')gene,whichencodesβlactamase（orpenicillinase，β-内酰胺酶），apenicillin-degradingenzyme.-CR-C-NH-eFCHhetaCHlactamringOCNCH-COOH1Siteofpenicillinaseaction(breakinβlactamring)15-15
Copyright © The McGraw-Hill Companies, Inc. Permission required to reproduce or display 15-15 Some R plasmids carry bla (Ampr) gene, which encodes - lactamase (or penicillinase, -内酰胺酶), a penicillin-degrading enzyme