Bacterial and Viral Genetic Systems Part I Ch. 8 Ebola virus Cholera bacteria H. pylori Outline Techniques to study bacteria The bacterial genome Plasmids Gene Transfer Mapping bacterial genes Antibiotic resistance Bacterial transformation Bacterial in vitro growth Liquid OR solid agar plates You will do in lab next week Bacterial Growth Minimal Growth Media Complete Growth Media For prototrophs For auxtrophs (mutants) Bacterial Colony Colonies are clones Mutant bacteria: can be found based on their food requirements Bacterial Genome (normallythere are exceptions) A circular chromosome Haploid Normally compact DNA NO nuclear membrane: prokaryoteno exception to this rule DNA escaping out of damaged cell Bacterial Plasmids 1.What are they? 2.What affect can they have on the bacterial cell? 3.How did they get inside the cell? 2 plasmids joined together Some plasmids are integrated And some remain independent. Episomes can be either! Episome The fertility factor (F factor) is an episome Controls gene exchange and mating in bacteria Methods for bacterial gene transfer (in nature) Conjugation Transformation Transduction You will do this in the lab! Methods for bacterial gene transfer (in nature) Conjugation: bacteria to bacteria Transformation: external environment to bug (bacteria) Transduction: from virus to bug! DNA transfer is not linked to reproduction in bacteria. Methods for bacterial gene transfer (in nature) Conjugation: often involves recombination Transformation: May have recombination Transduction: May have recombination How do we know? Experimental evidence to support bacterial recombination MINIMAL MEDIA NO GROWTH ON EITHER PLATE MIX STRAINS SOME GROWTH Most conjugation transfers requires the F factor Sex pilus Bacterial Recombination Certain bacterial cells show recombination with F factor These are called High-frequency (Hfr) cells Hfr cells and stepwise recombination Hfr cell to a F cell The F factor is cut from the bacterial chromosme and may even carry some bacterial chromosome with it! Partial diploids F can conjugate with F- cell. Leads to partial diploid= merozygotes Two copies of some genes Mapping bacterial genes Using interrupted conjugation Transfer times indicate map distances origin azi ton lacgal 25 R Plasmids Contain genes for antibiotic resistance Easily spread among unrelated bacteria Fish bacteria E. coli Transformation Uptake of DNA by bacteria from its external environment May be DNA fragment Bacterial cell must be competent May recombine with hosts DNA TRANSFORMANTS Transformation can be also used to map bacterial genes Note: You will carry out a bacterial transformation in lab next week; however, there will be some technical differences from what may occur in nature. I will emphasize these in lab. Next we complete chapter 8 Viral genetic systems