Changes in bacterial traits Caused by: Changes in environmental conditions (only phenotypic changes) Changes in the genetic codes 1- Intermicrobial exchange 2- Mutations (point mutations, insertions, deletions)

Intermicrobial exchange Transformation (Capturing DNA from solution) Transduction (Phage-mediated) Conjugation (Bacterial Sex)

Original Transformation Exp. F. Griffith (1928) using pneumococci

DNA-Mediated Transformation

Intermicrobial exchanges by vectors

8 Characteristics of genetic vectors must be capable of carrying a significant piece of donor DNA must be readily accepted by the host plasmids – small, well characterized, easy to manipulate & can be transferred into appropriate host cells through transformation bacteriophages – have the natural ability to inject their DNA into bacterial hosts through transduction

Transduction (madiated by phage)

Lytic versus Lysogenic

Generalized Transduction

Transduction Types of transduction  Generalized - Transduction in which potentially any dornor bacterial gene can be transferred.  Specialized (Restricted): Transduction in which only certain donor genes can be transferred.

Restricted Transduction (Lysogenic Phage) gal bio gal bio gal bio gal bio gal

Transduction Definition Types of transduction Significance  Common in Gram+ bacteria  Lysogenic (phage) conversion e.g. Corynebacterium diptheriae toxin Toxin derived from lysogenic phage

Conjugation

Conjugation Definition: Gene transfer from a donor to a recipient by direct physical contact between cells Mating types in bacteria  Donor F factor (Fertility factor)  F (sex) pilus Donor Recipient  Recipient Lacks an F factor

Conjugation Significance  Gram - bacteria Antibiotic resistance  Gram + bacteria Production of adhesive material by donor cells

Conjugation

Conjugation: Sex or F Pilus

Plasmids

Plasmids Definition: Extrachromosomal genetic elements that are capable of autonomous replication (replicon) Plasmid Types: Congugative & Non-congugative Congugative & Non-congugative Episome - a plasmid that can integrate into the chromosome Casmid – An integration of a plasmid and a bacteriophage

Phenotypic effects Fertility (F factor) Bacteriocinogenic (or encoding some other toxins) Resistance (R factors)

Structure of R Factors RTF  Conjugative plasmid  Transfer genes Tn 9 Tn 21 Tn 10 Tn 8 RTF R determinant  Resistance genes

Self-Transmissible R Plasmid

Conjugation: F Plasmid Transfer

F + and HFr cells Integrated (Hfr) (High Frequency of Recombination) F+F+ Hfr

Hfr and F’ cells Hfr F’

Mechanism of Hfr x F - Crosses HfrF-F- F-F- F-F- F-F-

Mechanism of F’ x F - Crosses F’ F-F- F-F-

Transposable Genetic Elements Definition: Segments of DNA that are able to move from one location to another (across the genome or from one genome to another) Properties  “Random” movement Transposase  Transposition may be accompanied by duplication

Types of Transposable Genetic Elements Transposons (Tn)/ Insertion elements (IS)  Definition: Elements that carry other genes in addition to those involved in transposition  Nomenclature - Tn10, IS6110  Structure Composite Tns  Importance Antibiotic resistance Epidemiology and evolutionary studies IS Resistance Gene(s) IS Resistance Gene(s)