RECOMBINATION in BACTERIA Transfer of Genetic Material In
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Topic: Genetic Recombination of Bacteria
COMPILED AND CIRCULATED BY ARPITA CHAKRABORTY, STATE AIDED COLLEGE TEACHER, DEPARTMENT OF BOTANY, NARAJOLE RAJ COLLEGE. Topic: Genetic Recombination of Bacteria Genetic Recombination of Bacteria: The following points highlight the three main processes involved in the genetic recombination of bacteria. The processes are: 1. Conjugation 2. Transformation 3. Transduction. Process- 1. Conjugation: In this process, the exchange of genetic material takes place through a conjugation tube between the two cells of bacteria. The process was first postulated by Joshua Lederberg and Edward Tatum (1946) in Escherichia coli. They were awarded the Nobel Prize in 1958 for their work on bacterial genetics. Later on, it has also been demonstrated in Salmonella, Vibrio and Pseudomonas. There are two mating types of bacteria, one is. male type or F+ or donor cell, which donates some DNA. The other one is female type or F– or recipient cell, which receives DNA. Later, after receiving DNA, the recipient cell may behave as donor cell i.e., F+ type. The F-factor is the fertility factor, sex-factor or F-plasmid present in the cell of F+ i.e., donor cell or male type. The plasmid takes part in conjugation is called episome. BOTANY: SEM- I, PAPER: C1T:PHYCOLOGY AND MICROBIOLOGY, UNIT 3: BACTERIA COMPILED AND CIRCULATED BY ARPITA CHAKRABORTY, STATE AIDED COLLEGE TEACHER, DEPARTMENT OF BOTANY, NARAJOLE RAJ COLLEGE. In this process, two cells of opposite mating type i.e., F+ and F– become temporarily attached with each other by sex pilus. The sex pilus has a hole of 2.5 pm diameter through which DNA can pass from donor to recipient cell. -
Bacterial Genetics
BACTERIAL GENETICS Genetics is the study of genes including the structure of genetic materials, what information is stored in the genes, how the genes are expressed and how the genetic information is transferred. Genetics is also the study of heredity and variation. The arrangement of genes within organisms is its genotype and the physical characteristics an organism based on its genotype and the interaction with its environment, make up its phenotype. The order of DNA bases constitutes the bacterium's genotype. A particular organism may possess alternate forms of some genes. Such alternate forms of genes are referred to as alleles. The cell's genome is stored in chromosomes, which are chains of double stranded DNA. Genes are sequences of nucleotides within DNA that code for functional proteins. The genetic material of bacteria and plasmids is DNA. The two essential functions of genetic material are replication and expression. Structure of DNA The DNA molecule is composed of two chains of nucleotides wound around each other in the form of “double helix”. Double-stranded DNA is helical, and the two strands in the helix are antiparallel. The backbone of each strand comprises of repeating units of deoxyribose and phosphate residue. Attached to the deoxyribose is purine (AG) or pyrimidine (CT) base. Nucleic acids are large polymers consisting of repeating nucleotide units. Each nucleotide contains one phosphate group, one deoxyribose sugar, and one purine or pyrimidine base. In DNA the sugar is deoxyribose; in RNA the sugar is ribose. The double helix is stabilized by hydrogen bonds between purine and pyrimidine bases on the opposite strands. -
Microbial Genetics by Dr Preeti Bajpai
Dr. Preeti Bajpai Genes: an overview ▪ A gene is the functional unit of heredity ▪ Each chromosome carry a linear array of multiple genes ▪ Each gene represents segment of DNA responsible for synthesis of RNA or protein product ▪ A gene is considered to be unit of genetic information that controls specific aspect of phenotype DNA Chromosome Gene Protein-1 Prokaryotic Courtesy: Team Shrub https://twitter.com/realscientists/status/927 cell 667237145767937 Genetic exchange within Prokaryotes The genetic exchange occurring in bacteria involve transfers of genes from one bacterium to another. The gene transfer in prokaryotic cells is thus unidirectional and the recombination events usually occur between a fragment of one chromosome (from a donor cell) and a complete chromosome (in a recipient cell) Mechanisms for genetic exchange Bacteria exchange genetic material through three different parasexual processes* namely transformation, conjugation and transduction. *Parasexual process involves recombination of genes from genetically distinct cells occurring without involvement of meiosis and fertilization Principles of Genetics-sixth edition Courtesy: Beatrice the Biologist.com by D. Peter Snustad & Michael J. Simmons (http://www.beatricebiologist.com/2014/08/bacterial-gifts/) Transformation: an introduction Transformation involves the uptake of free DNA molecules released from one bacterium (the donor cell) by another bacterium (the recipient cell). Frederick Griffith discovered transformation in Streptococcus pneumoniae (pneumococcus) in 1928. In his experiments, Griffith used two related strains of bacteria, known as R and S. The R bacteria (nonvirulent) formed colonies, or clumps of related bacteria, that Frederick Griffith 1877-1941 had a rough appearance (hence the abbreviation "R"). The S bacteria (virulent) formed colonies that were rounded and smooth (hence the abbreviation "S"). -
Transformation and Homologous Recombination in Mycoplasma Gallisepticum Jian Jian Iowa State University
Iowa State University Capstones, Theses and Retrospective Theses and Dissertations Dissertations 1-1-1993 Transformation and homologous recombination in Mycoplasma gallisepticum Jian Jian Iowa State University Follow this and additional works at: https://lib.dr.iastate.edu/rtd Recommended Citation Jian, Jian, "Transformation and homologous recombination in Mycoplasma gallisepticum" (1993). Retrospective Theses and Dissertations. 18012. https://lib.dr.iastate.edu/rtd/18012 This Thesis is brought to you for free and open access by the Iowa State University Capstones, Theses and Dissertations at Iowa State University Digital Repository. It has been accepted for inclusion in Retrospective Theses and Dissertations by an authorized administrator of Iowa State University Digital Repository. For more information, please contact [email protected]. Transformation and homologous recombination in Mycoplasma gallisepticum by Jian Cao A Thesis Submitted to the Graduate Faculty in Partial Fulfillment of the Requirements for the Degree of MASTER OF SCIENCE Department: Microbiology, Immunology and Preventive Medicine Major: Veterinary Microbiology "-- ... - .. - -J . Signatures have been redacted for privacy Iowa State University Ames, Iowa 1993 II TABLE OF CONTENTS LIST OF TABLES iv LIST OF FIGURES v LIST OF ABBREVIATIONS vi ACKNOWLEDGMENTS vii INTRODUCTION General Characteristics of Mycoplasmas Antigenic variation 1 Virulence factors 3 Chromosomal structure 4 Physical and genetic maps 4 Nucleotide composition and codon usage 5 Transformation and transposition -
Early Stages of Conjugation in Escherichia Coli ROY CURTISS, III, LUCIEN G
JOURNAL OF BACTERIOLOGY, Nov. 1969, p. 1091-1104 Vol. 100, No. 2 Copyright 0 1969 American Society for Microbiology Printed in U.S.A. Early Stages of Conjugation in Escherichia coli ROY CURTISS, III, LUCIEN G. CARO, DAVID P. ALLISON, AND DONALD R. STALLIONS Biology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830 Received for publication 8 September 1969 We initiated these studies to learn more about the initial events during bacterial conjugation and to optimize conditions for their occurrence. We found that cells in donor cultures grown anaerobically prior to mating have (i) a higher mean number of F pili per cell, (ii) longer F pili, (iii) a higher probability of forming specific pairs with F- cells, and (iv) a faster rate of initiation of chromosome transfer than cells grown aerobically. The growth medium for the donor culture also influences these same parameters: a rich medium is superior to a completely synthetic medium. Starvation of donor cells in buffered saline or for a required amino acid results in (i) a loss of F pili, (ii) a loss in the ability of donor-specific phages to adsorb, (iii) a loss of ability to form specific pairs with F- cells and to yield recombinants, and (iv) an increase in recipient ability. These changes occur as a function of starvation time, and at rates which are dependent on the conditions of prior growth and starvation of the donor culture. Either treatment provides a rapid method for the production of F- phenocopies from donor cultures. Resynthesis ofF pili by cells within a starved donor culture commences very soon after restoration of normal growth conditions, but full restoration of donor ability, as measured by recombinant yield, occurs at a slower rate. -
Difference Between HFR and F+ Strains Key Difference - HFR Vs F+ Strains
Difference Between HFR and F+ Strains www.differencebetween.com Key Difference - HFR vs F+ Strains Bacterial conjugation is a method of sexual reproduction in bacteria and is considered as one mode of horizontal gene transfer in bacteria. It is possible between two bacteria in which one bacterium possesses fertility factor or F plasmid and second bacterium lacks F plasmid. During bacterial conjugation, F plasmids are generally transferred to the recipient bacterium, not the entire chromosome. Bacteria which possess the F plasmids are known as F+ strains or donors. They are capable of forming sex pili and transferring plasmids into other bacteria which receive them. F plasmid is free in the cytoplasm. Sometimes, F plasmid integrates into the bacterial chromosome and produce recombinant DNA. Bacteria which possess F plasmid integrated into their chromosomes are known as high frequency recombinant strains or Hfr strains. The key difference between F+ strains and Hfr is that F+ strains have F plasmids in the cytoplasm freely without integrating into bacterial chromosomes while Hfr strains have F plasmids integrated to their chromosomes. What are F+ Strains? Some bacterial strains possess F plasmids in addition to their chromosomes. These strains are known as F+ strains. They act as donor cells or males in bacterial conjugation. Bacterial conjugation is a sexual reproduction mechanism shown by bacteria which facilitates horizontal gene transferring between bacteria. F plasmids can replicate independently and contain fertility factor coding genes. Hence these extrachromosomal DNA (plasmids) are named F plasmids due to the F factor or fertility factor. Fertility factor coding genes are essential for transfer or conjugation. -
Recombination of Escherzchza Colz and Bacteriophage Lambda
Symposium on Genetic Exchange : XIlI Internaiionul Congress of Genetics PROGRESS TOWARD A METABOLIC INTERPRETATION OF GENETIC RECOMBINATION OF ESCHERZCHZA COLZ AND BACTERIOPHAGE LAMBDA ALVIN J. CLARK Department of Molecular Biology, University of California, Berkeley, California 94720 is a metabolically active cellular component of bacteria. Transcrip- DNA tion and replication can proceed continuously throughout the growth and division of bacterial cells. Enzymes methylate DNA bases and when they have not acted restriction enzymes nick and break double-stranded DNA mole- cules producing substrates for further degradation. When radiations or chemicals damage DNA, repair enzymes either change or remove damaged portions, restor- ing the DNA to its original state, or they deal with secondary lesions produced by faulty metabolism of the unremoved primary lesions. In addition to these realms of DNA metabolism there is the realm of genetic recombination. A metabolic interpretation of genetic recombination will require knowledge of the structures of the starting materials and end products of recom- bination. It will also require a list of the enzymes or proteins catalyzing the steps in recombination together with their activities and substrate specificities and ultimately the intermediates and products of each step. Furthermore E! metabolic interpretation will require a knowledge of the regulation of the synthesis and activities of the enzymes and other proteins of recombination. Finally the rela- tionships between recombination and the other realms of DNA metabolism must be stated as a list of common and unique intermediates and enzymes. At present we are far from such a metabolic interpretation although consider- able progress has been made. In the present report I shall emphasize work per- formed in my own laboratory on the recombination of E. -
Bacterial Conjugation
16 Mechanisms of Genetic Variation 1 16.1 Mutations 1. Distinguish spontaneous from induced mutations, and list the most common ways each arises 2. Construct a table, concept map, or picture to summarize how base analogues, DNA-modifying agents, and intercalating agents cause mutations 3. Discuss the possible effects of mutations 2 Mutations: Their Chemical Basis and Effects • Stable, heritable changes in sequence of bases in DNA – point mutations most common • from alteration of single pairs of nucleotide • from the addition or deletion of nucleotide pairs – larger mutations are less common • insertions, deletions, inversions, duplication, and translocations of nucleotide sequences • Mutations can be spontaneous or induced 3 16.4 Creating Additional Genetic Variability 1. Describe in general terms how recombinant eukaryotic organisms arise 2. Distinguish vertical gene transfer from horizontal gene transfer 3. Summarize the four possible outcomes of horizontal gene transfer 4. Compare and contrast homologous recombination and site-specific recombination 4 Creating Additional Genetic Variability • Mutations are subject to selective pressure – each mutant form that survives becomes an allele, an alternate form of a gene • Recombination is the process in which one or more nucleic acids are rearranged or combined to produce a new nucleotide sequence (recombinants) 5 Sexual Reproduction and Genetic Variability • Vertical gene transfer = transfer of genes from parents to progeny • In eukaryotes – sexual reproduction is accompanied by genetic -
Molecular Biology
MOLECULAR BIOLOGY CONJUGATION GINCY C GEORGE (Assistant Professor On Contract) CONJUGATION In 1946 Joshua Lederberg and Tatum discovered that some bacteria can transfer genetic information to other bacteria through a process known as conjugation. Bacterial conjugation is the transfer of DNA from a living donor bacterium to a recipient bacterium. Plasmids are small autonomously replicating circular pieces of double-stranded circular DNA. Conjugation involves the transfer of plasmids from donor bacterium to recipient bacterium. Plasmid transfer in Gram-negative bacteria occurs only between strains of the same species or closely related species. Some plasmids are designated as F factor (F plasmid, fertility factor or sex factor) because they carry genes that mediate their own transfer. The F factor can replicate autonomously in the cell. These genes code for the production of the sex pilus and enzymes necessary for conjugation. Cells possessing F plasmids are F+ (male) and act as donors. Those cells lacking this plasmid are F- (female) and act as recipient. All those plasmids, which confer on their host cells to act as donors in conjugation are called transfer factor. Each Gram negative F+ bacterium has 1 to 3 sex pili that bind to a specific outer membrane protein on recipient bacteria to initiate mating. The sex pilus then retracts, bringing the two bacteria in contact and the two cells become bound together at a point of direct envelope-to-envelope contact. In Gram-positive bacteria sticky surface molecules are produced which bring the two bacteria into contact. Gram-positive donor bacteria produce adhesins that cause them to aggregate with recipient cells, but sex pili are not involved. -
Impact of Transgenic Technologies on Functional Genomics 75
Curr. Issues Mol. Biol. (2003) 5: 75-98. Impact of Transgenic Technologies on Functional Genomics 75 Impact of Transgenic Technologies on Functional Genomics Cooduvalli S. Shashikant1* and Frank H. Ruddle2 biotechnological capabilities. Twentieth century genetics was dominated by the idea 1 Dept. Dairy and Animal Science, College of Agricultural of introducing exogenous genetic material into the genome Sciences, 324 Henning, University Park, PA 16802, USA of experimental organisms. The foundation of bacterial 2 Depts of MCDB and Genetics, Yale University, New genetics lies in the discovery of transformation, conjugation Haven, CT 06511, USA and transduction. A combination of bacterial gene transfer technologies and molecular biology tools resulted in the birth of recombinant DNA technology in the seventies. The Abstract progress made in bacterial genetics inspired development of similar methods to study mammalian genetics. Here, Gene transfer technologies in mammals are the focus mammalian gene transfer technology is broadly considered of renewed interest owing to the recent emphasis on under three technological breakthroughs achieved during analyzing gene function in the postgenomic era. Three the past two decades: (a) transgenic technology; (b) gene important developments in this area include targeting; and (c) nuclear transfer or ‘cloning’. In this review, transgenics, gene targeting and nuclear transfer or we describe the emergence of these technologies and animal cloning. These technological innovations have current advances in the analysis of mammalian gene enhanced our ability to analyze gene function at the function. level of the whole organism and have provided the means to modify gene expression. This review Historical Perspective discusses the origins and current status of transgenic technologies. -
Double-Strand End Repair Via the Recbc Pathway in Escherichia Coli Primes DNA Replication
Downloaded from genesdev.cshlp.org on October 8, 2021 - Published by Cold Spring Harbor Laboratory Press Double-strand end repair via the RecBC pathway in Escherichia coli primes DNA replication Andrei Kuzminov1 and Franklin W. Stahl Institute of Molecular Biology, University of Oregon, Eugene, Oregon 97403-1229 USA To study the relationship between homologous recombination and DNA replication in Escherichia coli,we monitored the behavior of phage chromosomes, repressed or not for gene activities. Recombination in our system is stimulated both by DNA replication and by experimentally introduced double-strand ends, supporting the idea that DNA replication generates occasional double-strand ends. We report that the RecBC recombinational pathway of E. coli uses double-strand ends to prime DNA synthesis, implying a circular relationship between DNA replication and recombination and suggesting that the primary role of recombination is in the repair of disintegrated replication forks arising during vegetative reproduction. [Key Words: DSB repair; homologous recombination; DNA replication; recA; recD; recBC] Received October 15, 1998; revised version accepted December 22, 1998. Homologous recombination was first seen as the cross- 1998). soon emerged as a promising system, following ing-over of chromosomes in cells undergoing meiosis. the finding that it has homologous recombination (Jacob The first scheme of crossing-over (Janssens 1909) was of and Wollman 1954; Kaiser 1955) and that its growth is the break–join type, according to which homologous only partly dependent on recombination (Manly et al. chromosomes would break at the same position and 1969; Enquist and Skalka 1973). The experiments of Me- swap arms (Fig. 1). The copy-choice scheme (Belling selson and Weigle showed the presence of parental DNA 1931a, b) was the first to link homologous recombina- in recombinants, ruling out copy–choice as the only tion with chromosomal replication (Fig. -
Joshua Lederberg on Bacterial Recombination
| CLASSIC Joshua Lederberg on Bacterial Recombination Mark Johnston1 Department of Biochemistry and Molecular Genetics, University of Colorado School of Medicine, Aurora, Colorado 80045 ORCID ID: 0000-0002-4932-7229 (M.J.) ORIGINAL CITATION Gene Recombination and Linked Segregations in Escherichia coli Joshua Lederberg GENETICS September 1, 1947 32: 505–525 his paper describes the first genetic analysis of bacteria. Lederberg decided to take a different tack. Instead of trying TBefore its publication, most scientists wondered if bacteria to replicate DNA transformation in an existing model organ- even had genes. Many thought bacteria to be a distinct form ism, why not establish a new system for genetic analysis of of life, separate from higher organisms like Drosophila bacteria? The conventional wisdom was that bacteria do not and maize, which were known to follow Mendel’s principles engage in sex, which would make standard genetic analysis of heredity. But when George Beadle and Edward Tatum impossible. There had been a few attempts to detect genetic showed in 1941 that Neurospora obeys Mendel’slaws(Beadle exchange in bacteria, but the results were inconclusive. Lederberg and Tatum 1941), and 2 years later Salvador Luria and Max decided to give it another try. Why not? He knew he had Delbrück reported in GENETICS that bacterial mutations arise nothing to lose: he did not need to complete a research project at random (Murray 2016), microorganisms began to shed their to receive his MD degree. outsider status. Then, when Avery, McLeod, and McCarty iden- Lederberg chose to use Escherichia coli for these experi- tified DNA as the substance that stably converts one form of ments and started the painstaking process of mutagenizing Pneumococcus bacteria to another (Avery et al.