Bacteria Genetic Transfer PDF

Document Details

HottestConflict

Uploaded by HottestConflict

King Faisal University

Dr Lorina Badger - Emeka

Tags

bacteria genetics bacterial gene transfer molecular biology genetics

Summary

This document provides an overview of bacterial gene transfer, highlighting the mechanisms of transformation, transduction, and conjugation. It explains how these processes facilitate genetic exchange between bacterial cells, explaining their roles and significance. The document also explores relevant concepts like plasmids, transposons, and pathogenicity islands, contributing to a thorough understanding of bacterial genetics.

Full Transcript

Bacteria Genetic Transfer Dr Lorina Badger - Emeka COM - KFU Intended Learning Outcomes 1 Students should be able to: Know what plasmids, bacteriophages, transposons and pathogenicity islands are.  Know the purpose for Quorum sensing Know the role of plasmids, ph...

Bacteria Genetic Transfer Dr Lorina Badger - Emeka COM - KFU Intended Learning Outcomes 1 Students should be able to: Know what plasmids, bacteriophages, transposons and pathogenicity islands are.  Know the purpose for Quorum sensing Know the role of plasmids, phages and transposons in gene transfer via: - conjugation, - transformation; - transduction Intended Learning Outcomes 2 Students should be able to know:  Know the role of recombination in bacteria gene transfer. Introduction Acquiring genes through genetic transfer provides,  new genetic information to microorganisms and this may help them to survive changing environments Importance of genetic transfer From a clinical perspective, - it aids in the transfer of antibiotic resistance genes from resistant bacterial to sensitive ones. Plasmids and bacteriophages can also give other factors (such as virulence genes e.g. toxins) to bacteria who previously didn’t have them. The Bacterial gene and Expression Bacteria have only one chromosome They may also contain extra chromosomal genetic elements such as  plasmids and bacteriophages (bacteria viruses) These elements are independent of the bacterial chromosome and  can be transmitted from one cell to another. Plasmids 1 Antibiotic susceptibility and plasmid profile of clinical isolates of Escherichia coli. Badger-Emeka et al., 2018 Plasmids 2 Plasmids are small genetic elements They can replicate independently of the bacterial chromosome.  They can also provide for genetic change. Plasmids carry genetic information, Plasmids 3 The F plasmid is important for conjugation  R plasmids which carry genes that confer resistance to certain antibiotics They can be transferred by conjugation from one bacteria cell to another Importance? Without resistance genes for a particular antibiotic,  a bacterium is sensitive to that antibiotic Plasmids Cont’d Bacteriophages 1 Bacteriophages are bacterial viruses. With either a DNA or RNA genome usually protected by a protein shell. They can survive outside of a host cell and be transmitted from one cell to another. Bacteriophages infect bacterial cells. Bacteriophages 2 Bacteria Chromosome The bacteria genome is the total of genes carried by a bacteria both on it’s Chromosomal and extrachromosomal genetic elements Pathogenicity Islands Genes may also be grouped in islands, such as  the pathogenicity islands, Which share function or to coordinate their control. Pathogenicity islands are found in:  Gram-negative and Gram-positive bacteria. Pathogenicity Islands 2 The genes for some virulence mechanisms are organized into a pathogenicity island Quorum Sensing In a process called quorum sensing,  when a sufficient number (quorum) of bacteria are present and producing a specific small molecule,  virulence and other genes are turned on. Quorum Sensing Examples  E.g., when sufficient numbers of bacteria (a quorum) are present:  Activation of toxin production and more virulent behaviour by Staphylococcus aureus  is accomplished by the increase in a cyclic peptide concentration.  The biofilm production by Pseudomonas spp. Is triggered by:  critical concentration of N-acyl homoserine lactone (AHL) produced. Transposons Transposons are transferable genetic elements in the genome, They are mobile in nature  They can jump from one position to the other within the genome. There are two types namely:  replicative and non-replicative transposons Transposons 2 Transposons are pieces of DNA  they can move from: one location on the chromosome to another,  from plasmid to chromosome or vice versa or from one plasmid to another Genetic transfer The mechanism by which DNA is transferred from one donor to a recipient In bacteria, genetic transfer can occur in three ways: 1. transformation 2. transduction 3. conjugation A recombination event must occur after transfer in order for the change in genome to be heritable. Microbial genetic transfer between cells 1. Conjugation 2. transformation 3. transduction Conjugation Conjugation occurs between members of the same species The process involves an exchange of genetic information. It is a one-way transfer of DNA from donor (male) cell to the recipient cell (female). Conjugation: Fig. Conjugation Cont’d Plasmids may contain genes that allow a bridge (pilus) to form between two bacteria. Bacteria with these plasmids are F+ The plasmid from the F+ (donor) bacterium is replicated and transferred to the F- (recipient) bacterium Summary Question 1 Which one of the following method of gene transfer involves direct contact between the bacteria?  A) Conjugation.  B) Transduction.  C) Transformation. Transformation DNA is released at the death or lysing of bacteria, Other bacterial, of the same species, take up these fragments and  incorporate them into their DNA by recombination This method of transfer is the process of transformation. This genetically transformed cell is called a recombinant cell. TRANSFORM ATION 1 TRANSFORM ATION 2 Transduction This is another method for genetic transfer Here, DNA is transferred from one bacterium to another with the use of a bacteriophage (phage) TRANSDUCTI ON cont’d Genetic recombination This refers to the exchange between two DNA molecules  It results in new combinations of genes on the chromosome The process involves the crossing over of two homologous chromosomes  Recombination can give rise to genetic diversity in a population. High frequency recombinations Genetic mechanisms of evolution of methicillin- and vancomycin-resistant Staphylococcus aureus (MRSA and MVRSA). Vancomycin-resistant Summary REFERENCES MEDICAL MICROBIOLOGY.  BY  MURRAY ROSENTHAL PFALLER. 7TH ED. Chapter 13, pg. 125 - 127 ALL IMAGES ARE COURTESY OF GOOGLE 8th Edition: Chapter 13; pg. 121 – 123; 129 - 132

Use Quizgecko on...
Browser
Browser