Bacterial Conjugation
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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. -
Mobile Genetic Elements in Streptococci
Curr. Issues Mol. Biol. (2019) 32: 123-166. DOI: https://dx.doi.org/10.21775/cimb.032.123 Mobile Genetic Elements in Streptococci Miao Lu#, Tao Gong#, Anqi Zhang, Boyu Tang, Jiamin Chen, Zhong Zhang, Yuqing Li*, Xuedong Zhou* State Key Laboratory of Oral Diseases, National Clinical Research Center for Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, PR China. #Miao Lu and Tao Gong contributed equally to this work. *Address correspondence to: [email protected], [email protected] Abstract Streptococci are a group of Gram-positive bacteria belonging to the family Streptococcaceae, which are responsible of multiple diseases. Some of these species can cause invasive infection that may result in life-threatening illness. Moreover, antibiotic-resistant bacteria are considerably increasing, thus imposing a global consideration. One of the main causes of this resistance is the horizontal gene transfer (HGT), associated to gene transfer agents including transposons, integrons, plasmids and bacteriophages. These agents, which are called mobile genetic elements (MGEs), encode proteins able to mediate DNA movements. This review briefly describes MGEs in streptococci, focusing on their structure and properties related to HGT and antibiotic resistance. caister.com/cimb 123 Curr. Issues Mol. Biol. (2019) Vol. 32 Mobile Genetic Elements Lu et al Introduction Streptococci are a group of Gram-positive bacteria widely distributed across human and animals. Unlike the Staphylococcus species, streptococci are catalase negative and are subclassified into the three subspecies alpha, beta and gamma according to the partial, complete or absent hemolysis induced, respectively. The beta hemolytic streptococci species are further classified by the cell wall carbohydrate composition (Lancefield, 1933) and according to human diseases in Lancefield groups A, B, C and G. -
Gene Linkage and Genetic Mapping 4TH PAGES © Jones & Bartlett Learning, LLC
© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Gene Linkage and © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC 4NOTGenetic FOR SALE OR DISTRIBUTIONMapping NOT FOR SALE OR DISTRIBUTION CHAPTER ORGANIZATION © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR4.1 SALELinked OR alleles DISTRIBUTION tend to stay 4.4NOT Polymorphic FOR SALE DNA ORsequences DISTRIBUTION are together in meiosis. 112 used in human genetic mapping. 128 The degree of linkage is measured by the Single-nucleotide polymorphisms (SNPs) frequency of recombination. 113 are abundant in the human genome. 129 The frequency of recombination is the same SNPs in restriction sites yield restriction for coupling and repulsion heterozygotes. 114 fragment length polymorphisms (RFLPs). 130 © Jones & Bartlett Learning,The frequency LLC of recombination differs © Jones & BartlettSimple-sequence Learning, repeats LLC (SSRs) often NOT FOR SALE OR DISTRIBUTIONfrom one gene pair to the next. NOT114 FOR SALEdiffer OR in copyDISTRIBUTION number. 131 Recombination does not occur in Gene dosage can differ owing to copy- Drosophila males. 115 number variation (CNV). 133 4.2 Recombination results from Copy-number variation has helped human populations adapt to a high-starch diet. 134 crossing-over between linked© Jones alleles. & Bartlett Learning,116 LLC 4.5 Tetrads contain© Jonesall & Bartlett Learning, LLC four products of meiosis. -
Horizontal Gene Transfer
Genetic Variation: The genetic substrate for natural selection Horizontal Gene Transfer Dr. Carol E. Lee, University of Wisconsin Copyright ©2020; Do not upload without permission What about organisms that do not have sexual reproduction? In prokaryotes: Horizontal gene transfer (HGT): Also termed Lateral Gene Transfer - the lateral transmission of genes between individual cells, either directly or indirectly. Could include transformation, transduction, and conjugation. This transfer of genes between organisms occurs in a manner distinct from the vertical transmission of genes from parent to offspring via sexual reproduction. These mechanisms not only generate new gene assortments, they also help move genes throughout populations and from species to species. HGT has been shown to be an important factor in the evolution of many organisms. From some basic background on prokaryotic genome architecture Smaller Population Size • Differences in genome architecture (noncoding, nonfunctional) (regulatory sequence) (transcribed sequence) General Principles • Most conserved feature of Prokaryotes is the operon • Gene Order: Prokaryotic gene order is not conserved (aside from order within the operon), whereas in Eukaryotes gene order tends to be conserved across taxa • Intron-exon genomic organization: The distinctive feature of eukaryotic genomes that sharply separates them from prokaryotic genomes is the presence of spliceosomal introns that interrupt protein-coding genes Small vs. Large Genomes 1. Compact, relatively small genomes of viruses, archaea, bacteria (typically, <10Mb), and many unicellular eukaryotes (typically, <20 Mb). In these genomes, protein-coding and RNA-coding sequences occupy most of the genomic sequence. 2. Expansive, large genomes of multicellular and some unicellular eukaryotes (typically, >100 Mb). In these genomes, the majority of the nucleotide sequence is non-coding. -
Transduction by Bacteriophage Ti * Henry Drexler
Proceedings of the National Academy of Sciences Vol. 66, No. 4, pp. 1083-1088, August 1970 Transduction by Bacteriophage Ti * Henry Drexler DEPARTMENT OF MICROBIOLOGY, BOWMAN GRAY SCHOOL OF MEDICINE, WAKE FOREST UNIVERSITY, WINSTON-SALEM, NORTH CAROLINA Communicated by Edward L. Tatum, May 25, 1970 Abstract. Amber mutants of the virulent coliphage T1 are able to transduce a wide variety of genetic characteristics from permissive to nonpermissive K strains of Escherichia coli. The virulent coliphage T1 is not known to be related to any temperate phage. Certain of the characteristics of T1 seem to be incompatible with its potential existence as a temperate phage; for example, the average latent period for T1 is only 13 min' and about 70% of its DNA is derived from the host.2 In order to demonstrate transduction by T1 it is necessray to provide condi- tions in which potential transductants are able to survive; this is accomplished by using amber mutants of T1 to transduce nonpermissive recipients. Experi- ments which show that T1 is a transducing phage are presented and have been designed chiefly to illustrate the following points: (1) Infection by T1 is able to cause heritable changes in recipients; (2) the genotype of the donor host is im- portant in determining what characteristics can be transferred to recipients; (3) the changes in the recipients are not caused by transformation; and (4) there is a similarity between the transducing activity and the plaque-forming ability of T1 with respect to serology, host range, and density. Materials and Methods. Bacterial strains: The abbreviations and symbols of Demerec et al.3 and Taylor and Trotter4 are used to describe all pertinent genotypes. -
Genetic Recombination Promote Genetic Diversity in Prokaryotes
CAMPBELL TENTH BIOLOGY EDITION Reece • Urry • Cain • Wasserman • Minorsky • Jackson 27 Bacteria and Archaea Lecture Presentation by Nicole Tunbridge and Kathleen Fitzpatrick © 2014 Pearson Education, Inc. Masters of Adaptation . Utah’s Great Salt Lake can reach a salt concentration of 32% . Its pink color comes from living prokaryotes © 2014 Pearson Education, Inc. Figure 27.1 © 2014 Pearson Education, Inc. Prokaryotes thrive almost everywhere, including places too acidic, salty, cold, or hot for most other organisms . Most prokaryotes are microscopic, but what they lack in size they make up for in numbers . There are more in a handful of fertile soil than the number of people who have ever lived . Prokaryotes are divided into two domains: bacteria and archaea © 2014 Pearson Education, Inc. Concept 27.1: Structural and functional adaptations contribute to prokaryotic success . Earth’s first organisms were likely prokaryotes . Most prokaryotes are unicellular, although some species form colonies . Most prokaryotic cells are 0.5–5 µm, much smaller than the 10–100 µm of many eukaryotic cells . Prokaryotic cells have a variety of shapes . The three most common shapes are spheres (cocci), rods (bacilli), and spirals © 2014 Pearson Education, Inc. Figure 27.2 1 µm 1 µm 3 µm (a) Spherical (b) Rod-shaped (c) Spiral © 2014 Pearson Education, Inc. Figure 27.2a 1 µm (a) Spherical © 2014 Pearson Education, Inc. Figure 27.2b 1 µm (b) Rod-shaped © 2014 Pearson Education, Inc. Figure 27.2c 3 µm (c) Spiral © 2014 Pearson Education, Inc. Cell-Surface Structures . An important feature of nearly all prokaryotic cells is their cell wall, which maintains cell shape, protects the cell, and prevents it from bursting in a hypotonic environment . -
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. -
Recombination in Bacteria
Recombination in Bacteria 1. Conjugation DNA from a donor cell is transferred to a recipient cell through a conjugation tube (pili). 2. Transformation Uptake of naked DNA molecule from remains of one bacterium (donor cell) by another bacterium (recipient cell). 3. Transduction Bacterial genes are carried from a donor cell to a recipient cell by a bacteriophage. { Generalized { Specialized Conjugation Ability to conjugate located on the F-plasmid F+ Cells act as donors F- Cells act as recipients F+/F- Conjugation: { F Factor “replicates off” a single strand of DNA. { New strand goes through pili to recipient cell. { New strand is made double stranded. { If entire F-plasmid crosses, then recipient cell becomes F+, otherwise nothing happens Conjugation with Hfr Hfr cell (High Frequency Recombination) cells have F-plasmid integrated into the Chromosome. Integration into the Chromosome is unique for each F-plasmid strain. When F-plasmid material is replicated and sent across pili, Chromosomal material is included. (Figure 6.10 in Klug & Cummings) When chromosomal material is in recipient cell, recombination can occur: { Recombination is double stranded. { Donor genes are recombined into the recipient cell. { Corresponding genes from recipient cell are recombined out of the chromosome and reabsorbed by the cell. Interrupted Mating Mapping 1. Allow conjugation to start Genes closest to the origin of replication site (in the direction of replication) are moved through the pili first. 2. After a set time, interrupt conjugation Only those genes closest to the origin of replication site will conjugate. The long the time, the more that is able to conjugate. 3. -
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"). -
A Mechanism for Genetic Recombination Generating One Parent and One Recombinant* by Thierry Boon and Norton D
A MECHANISM FOR GENETIC RECOMBINATION GENERATING ONE PARENT AND ONE RECOMBINANT* BY THIERRY BOON AND NORTON D. ZINDER ROCKEFELLER UNIVERSITY, NEW YORK Communicated August 18, 1969 Abstract.-A mechanism is proposed for generating one parental and one re- combinant genome in a single recombination event between two DNA mole- cules. Three stages of the event are described: initiation, replication, and re- turn. Initiation requires breakage and joining of strands. Replication pro- ceeds through a biparental "replication fork" generated in initiation. Return also involves breakage and joining of strands. Some of the implications of such a mechanism for genetic recombination are discussed. Introduction.-We have undertaken a study of the products of recombination of bacteriophage fil under conditions in which the parental genomes cannot replicate in the cell prior to recombination. The results obtained suggest that the products of one recombination event between two parental genomes are one parental genome and one recombinant genome. Previous studies of genetic recombination in bacteriophage did not demon- strate a correlation between the yields of reciprocal recombinants produced in single cells.2-5 Similarly, recombination between closely linked markers is often nonreciprocal in Neurospora and other fungi.6' 7 Although the results with phage f, are still preliminary, we wish to propose a mechanism of recom- bination having main features that are compatible with such nonreciprocal events. This mechanism involves breakage and joining of DNA strands and also requires DNA synthesis. Description of the Mechanism. -The DNA of phage f1 (similar to M13 and fd) is single stranded and circular.8 It has a molecular weight of about 1.7 X 106.9 After entrance into the host cell this DNA is transformed into a circular double-stranded form.10' 11 As the mechanism to be proposed is primarily aimed at understanding the recombina- tion events in phage fl, we describe it, using two double-stranded circular DNA molecules as parents. -
Comprehensive Analysis of Mobile Genetic Elements in the Gut Microbiome Reveals Phylum-Level Niche-Adaptive Gene Pools
bioRxiv preprint doi: https://doi.org/10.1101/214213; this version posted December 22, 2017. The copyright holder for this preprint (which was not certified by peer review) is the author/funder. All rights reserved. No reuse allowed without permission. 1 Comprehensive analysis of mobile genetic elements in the gut microbiome 2 reveals phylum-level niche-adaptive gene pools 3 Xiaofang Jiang1,2,†, Andrew Brantley Hall2,3,†, Ramnik J. Xavier1,2,3,4, and Eric Alm1,2,5,* 4 1 Center for Microbiome Informatics and Therapeutics, Massachusetts Institute of Technology, 5 Cambridge, MA 02139, USA 6 2 Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA 7 3 Center for Computational and Integrative Biology, Massachusetts General Hospital and Harvard 8 Medical School, Boston, MA 02114, USA 9 4 Gastrointestinal Unit and Center for the Study of Inflammatory Bowel Disease, Massachusetts General 10 Hospital and Harvard Medical School, Boston, MA 02114, USA 11 5 MIT Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA 12 02142, USA 13 † Co-first Authors 14 * Corresponding Author bioRxiv preprint doi: https://doi.org/10.1101/214213; this version posted December 22, 2017. The copyright holder for this preprint (which was not certified by peer review) is the author/funder. All rights reserved. No reuse allowed without permission. 15 Abstract 16 Mobile genetic elements (MGEs) drive extensive horizontal transfer in the gut microbiome. This transfer 17 could benefit human health by conferring new metabolic capabilities to commensal microbes, or it could 18 threaten human health by spreading antibiotic resistance genes to pathogens. Despite their biological 19 importance and medical relevance, MGEs from the gut microbiome have not been systematically 20 characterized. -
Genetic Engineering and Protein Synthesis
Key: Yellow highlight = required component Genetic Engineering and Protein Synthesis Subject Area(s) Biology Life Science Curricular Unit Title What does DNA do? Header Image 1 Image file: DNA.gif ADA Description: A computer generated model of DNA Source/Rights: Copyright © Spiffistan, Wikimedia Commons (http://commons.wikimedia.org/wiki/File:Bdna_cropped.gif) Caption: Double Stranded DNA structure Grade Level 9 (9-12) Summary This unit begins with an introduction to genetic engineering to grab the students attention before moving on to some basic biology topics. The entire gene expression process is covered, focusing on DNA transcription/translation and how this relates to protein synthesis. Mutations are also covered at the end of this unit to emphasize that changes to DNA are not always intentional. Multiple activities are included to help the students better understand the lessons. Engineering Connection Version: August 2013 1 Genetic engineering is a field with a growing number of practical applications. Engineers have developed genetic recombination techniques to manipulate gene sequences to have organisms express specific traits. It is integral that genetic engineers understand how traits are expressed and what effects will be produced by altering the DNA of an organism. Gene expression is a result of the protein synthesis process which reads DNA as a set of instructions for building specific proteins. Once this process is well understood, and genes are classified based on the desired trait, engineers develop ways to alter the genes to create a net benefit to us or the organism. This could include anything such as larger cows that produce more meat, pest resistant crops, or bacteria that produce fuel.