Chapter 13Bacterial Genetics15-1
Copyright © The McGraw-Hill Companies, Inc. Permission required to reproduce or display 15-1 Bacterial Genetics Bacterial Genetics Chapter 13
Sectionsto study13.1The enormous diversity of bacteria13.2Bacterialgenomes13.3 Bacteria as experimental organisms13.4Gene transferin bacteria13.5Bacterial genetic analysis15-2
Copyright © The McGraw-Hill Companies, Inc. Permission required to reproduce or display 15-2 Sections to study Sections to study 13.1 The enormous diversity of bacteria 13.1 The enormous diversity of bacteria 13.2 Bacterial genomes 13.2 Bacterial genomes 13.3 Bacteria as experimental organisms 13.3 Bacteria as experimental organisms 13.4 Gene transfer in bacteria 13.4 Gene transfer in bacteria 13.5 Bacterial genetic analysis 13.5 Bacterial genetic analysis
13.1 The enormous diversity of bacteriaOutnumber all other organisms on earth.10,000 speciesidentified.BacteriaArchaeaEukaryaAnimalssoSlimeEntoamoebaejemoldsFungiChloroflexusMethanothermus HalophilesPlantsMethanococcusCiliatesPurple bacteriaThermoproteusChloroplastPyrodictiumThermococcusFlagellatesCyanobactenaFlavobacteriaTrichonomadsThemotogalesMicrosponidiaAquifexDiplomonadsCommonAncestorFig 13.115-3
Copyright © The McGraw-Hill Companies, Inc. Permission required to reproduce or display 15-3 13.1 The enormous diversity of bacteria 13.1 The enormous diversity of bacteria Fig 13.1 Outnumber all other organisms on earth. Outnumber all other organisms on earth. 10,000 species identified. 10,000 species identified
Bacteriavaryin sizeand shapeSmallest 200 nmin diameter,thelargest500 um in lengthBacillusBordetellaClostridiumEscherichiaSpirulinaStaphyiococcusStreptococcusSaimonella15-4
Copyright © The McGraw-Hill Companies, Inc. Permission required to reproduce or display 15-4 Bacteria vary in size and shape Bacteria vary in size and shape Smallest 200 nm in diameter, the largest 500 Smallest 200 nm in diameter, the largest 500 m in length. m in length
Common features of bacteriaLack defined nuclear membrane.Chromosomes fold to form anucleoid body.Lackmembranebound organellesMost have a cell wall. Some has a mucus-like coating called acapsule.Manymovebyflagella.NucleoidPlasmidbodyCytoplasmFlagellumCellmembraneCell wallCapsuleFig 13.315-5
Copyright © The McGraw-Hill Companies, Inc. Permission required to reproduce or display 15-5 Lack defined nuclear membrane. Chromosomes fold to form a Lack defined nuclear membrane. Chromosomes fold to form a nucleoid nucleoid body. Lack membrane bound organelles. Lack membrane bound organelles. Most have a Most have a cell wall cell wall. Some has a mucus . Some has a mucus-like coating called a like coating called a capsule capsule. Many move by Many move by flagella flagella. Common features of bacteria Common features of bacteria Fig 13.3
BacteriahavediversemetabolismsRemarkable metabolic diversityallows them to live almostanywhere.Habitats rangefromland,to aquatic,toparasitic Can obtain energyfrom sunlight or breaking down chemicals.Bacteria are crucial to the maintenance of earth's environmentCanfixnitrogen,decomposeoilandotherchemicals.Nitrogen in atmosphere (N2)PlantsAssimllationDenitrilyingbacteriaNitratesNitrogen-fixing(NO,)bacteria in rootnadulesofDecomposers(aerobiclegumesandanaerobicbactoria andfungl)NitrityingbacteriaAmmonificationNitrificationAmmonlum(NH,)Nitrites (NO2)NitrityingNitrogen-fixing soil bacteriabacteria
Copyright © The McGraw-Hill Companies, Inc. Permission required to reproduce or display 15-6 Remarkable metabolic diversity allows them to live almost Remarkable metabolic diversity allows them to live almost anywhere. anywhere. Habitats range from land, to aquatic, to parasitic. Habitats range from land, to aquatic, to parasitic. Can obtain energy from sunlight or breaking down chemicals. Can obtain energy from sunlight or breaking down chemicals. Bacteria are crucial to the maintenance of earth Bacteria are crucial to the maintenance of earth’s environment. s environment. Can fix nitrogen, decompose oil and other chemicals. Can fix nitrogen, decompose oil and other chemicals. Bacteria have diverse metabolisms Bacteria have diverse metabolisms
Bacteria must be grown and studied in culturesCulture: The visible accumulation of microorganisms in or on anutrient medium.Also, the propagation of microorganisms withvarious media.On agar plate-A single bacterium can multiply to 107-108cells in less than a day.In liquid media-E.coligrows to concentration of 1o'cells/mlwithin a day.Fig13.1115-7
Copyright © The McGraw-Hill Companies, Inc. Permission required to reproduce or display 15-7 On agar plate On agar plate – A single bacterium can multiply to 10 A single bacterium can multiply to 107 – 108 cells in less than a day. cells in less than a day. In liquid media In liquid media – E. coli E. coli grows to concentration of 10 grows to concentration of 109 cells/ml cells/ml within a day. within a day. Bacteria must be grown and studied in cultures Bacteria must be grown and studied in cultures Culture: The visible accumulation of microorganisms in or on a nutrient medium. Also, the propagation of microorganisms with various media. Fig 13.11
Escherichia coli:A versatile model organismInhabitantofintestinesinwarmblooded animalsStrainsin laboratoryarenotpathogenic.Makes all the enzymes it needs for amino acid and nucleotidesynthesis.Prototroph-A microorganism that grows on minimal media.It isusually wild type.Rapid multiplication makes it possible to observe very raregenetic events.Divides about once every hour in minimal media and every 20 minutesin enriched media15-8
Copyright © The McGraw-Hill Companies, Inc. Permission required to reproduce or display 15-8 Escherichia coli: A versatile model organism Inhabitant of intestines in Inhabitant of intestines in warm blooded animals. warm blooded animals. Strains in laboratory are not Strains in laboratory are not pathogenic. pathogenic. Makes all the enzymes it needs Makes all the enzymes it needs for amino acid and nucleotide for amino acid and nucleotide synthesis. synthesis. Prototroph Prototroph – A microorganism that grows on minimal media. It is A microorganism that grows on minimal media. It is usually wild type. usually wild type. Rapid multiplication makes it possible to observe very rare Rapid multiplication makes it possible to observe very rare genetic events. genetic events. Divides about once every hour in minimal media and every 20 minu Divides about once every hour in minimal media and every 20 minutes in enriched media. in enriched media
13.2Bacterialgenomes4-5MblongCircularCondenses by supercoiling and looping into a denselypacked nucleoid bodyChromosomes replicate inside cell and cell divides bybinary fission.Diagrammaticrepresentationsofbacterialchromosome15-9Fig.13.4,13.5
Copyright © The McGraw-Hill Companies, Inc. Permission required to reproduce or display 15-9 13.2 Bacterial genomes 13.2 Bacterial genomes 4-5 Mb long 5 Mb long Circular Circular Condenses by Condenses by supercoiling supercoiling and looping into a densely and looping into a densely packed nucleoid nucleoid body. Chromosomes replicate inside cell and cell divides by Chromosomes replicate inside cell and cell divides by binary fission binary fission. Fig. 13.4, 13.5
Genes are tightly packed in bacterial genomesThegenome ofE.coliK12strain:aralac4.6 million base pairsmal4288genes,40%of which weReplicationFeplichore1sucdo not know what they doariginAlmost no repeated DNA.xylE.coli90%ofgenomeencodesK-12MG1655flgprotein.4,639,221bpdam--车Thelargestclass:427geneshave a transport functionRepliahore2ReplicationterminationBacteriophage sequencesfoundin8places (musthavemutsbeen invaded by viruses at1least8timesduringhistory)15-10
Copyright © The McGraw-Hill Companies, Inc. Permission required to reproduce or display 15-10 Genes are tightly packed in bacterial genomes Genes are tightly packed in bacterial genomes 4.6 million base pairs. 4288 genes, 40% of which we do not know what they do. Almost no repeated DNA. 90% of genome encodes protein. The largest class: 427 genes have a transport function. Bacteriophage sequences found in 8 places (must have been invaded by viruses at least 8 times during history). The genome of E. coli K12 strain: