微生物基因组（副本）.ppt

Three Models for Conjugation 2. Hfr Conjugation F factor integrate into the bacterial chromosome to make the hfr stain. DNA transfer begins when the integrated F factor is nicked at its site of transfer origin. As it is replicated, the chromosome moves through the pilus or conjugation bridge connecting the donor and recipient. Three Models for Conjugation 3. F’ Conjugation F’ plasmid is F plasmid plus a portion of the chromosomal material when error in excision. F’ X F- conjugation is virtually identical with F+ X F- mating. * Microbial Genetics Chapter 10 Outline 10.1 10.2 10.3 Microbial Genomes Other Genetic Materials Bacterial Plasmids Transposable Elements Movement of Bacterial Genetic materials DNA Recombination Transfer of DNA 10.1 Microbial Genome Genome: the genome of an organism is its set of chromosomes, containing all of its genes and associated DNA Bacterial genome usually is haploid, while eukaryotic microorganisms are diploid Many genome sequences have been completed and published, which may contribute significantly to the understanding of evolution and help deduce which genes are responsible for various cellular processes E.Coli K12 Genetic Map Outline 10.1 10.2 10.3 Microbial Genomes Other Genetic Materials Bacterial Plasmids Transposable Elements Movement of Bacterial Genetic materials DNA Recombination Transfer of DNA 10.2 Other Genetic Materials Except chromosome, there still have other genetic materials, like plasmids and transposable elements. Plasmids: in all kinds of microorganisms Transposable elements: in both prokaryotic and eukaryotic cells Bacterial Plasmids Plasmid: small dsDNA molecules, usually circular, that can exist independently of host chromosomes and are present in many bacteria (also in some yeasts and other fungi); have own replication origins and are autonomously replicating and stably inherited Plasmids have relatively few genes, which is not essential to the host Types of Plasmids Pl