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Author: Mark Michael Harden (Jr.)
Publisher:
ISBN:
Category :
Languages : en
Pages : 137
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Book Description
Conjugative elements are mobile genetic elements that can transfer from a donor bacterium to a recipient via an element-encoded type IV secretion system. Integrative and conjugative elements (ICEs) are an abundant class of conjugative element. ICEs are typically integrated into the bacterial host chromosome, but under certain conditions, or stochastically, they can excise from the chromosome and transfer to a recipient. ICEs likely interact with their bacterial host at every stage of their life cycle, but few of these interactions have been characterized. In this work I sought to 1) identify bacterial host factors necessary for efficient transfer of the integrative and conjugative element ICEBs1 to a recipient, and 2) determine whether the ICEBs1-encoded cell wall-modifying enzyme CwlT acts on the cell wall of the donor bacterium, the recipient bacterium, or both. I used CRISPR interference to induce a knockdown of individual essential Bacillus subtilis genes, and then screened for gene knockdowns that caused an acute defect in transfer of ICEBs1. I found that wall teichoic acids were necessary in both ICEBs1 donors and recipients for efficient conjugative transfer. I found that depletion of wall teichoic acids caused cells involved in ICEBs1 conjugation to sustain lethal envelope damage caused by active conjugation machinery. Conjugative elements must bypass the cell wall of both the donor and recipient cells in a mating pair. Conjugative elements encode cell wall hydrolases that are required for efficient transfer, which are presumed to partly degrade the cell wall of the donor bacterium during conjugation. In order to investigate the role of the ICEBs1-encoded cell wall hydrolase CwlT in conjugation, I generated cell wall-less (L-form) strains of B. subtilis which could donate or receive ICEBs1. In the absence of either the donor or recipient cell wall, CwlT was dispensable for efficient transfer. This finding indicates that CwlT acts on both the donor and recipient cell wall in a mating pair.
Author: Mark Michael Harden (Jr.)
Publisher:
ISBN:
Category :
Languages : en
Pages : 137
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Book Description
Conjugative elements are mobile genetic elements that can transfer from a donor bacterium to a recipient via an element-encoded type IV secretion system. Integrative and conjugative elements (ICEs) are an abundant class of conjugative element. ICEs are typically integrated into the bacterial host chromosome, but under certain conditions, or stochastically, they can excise from the chromosome and transfer to a recipient. ICEs likely interact with their bacterial host at every stage of their life cycle, but few of these interactions have been characterized. In this work I sought to 1) identify bacterial host factors necessary for efficient transfer of the integrative and conjugative element ICEBs1 to a recipient, and 2) determine whether the ICEBs1-encoded cell wall-modifying enzyme CwlT acts on the cell wall of the donor bacterium, the recipient bacterium, or both. I used CRISPR interference to induce a knockdown of individual essential Bacillus subtilis genes, and then screened for gene knockdowns that caused an acute defect in transfer of ICEBs1. I found that wall teichoic acids were necessary in both ICEBs1 donors and recipients for efficient conjugative transfer. I found that depletion of wall teichoic acids caused cells involved in ICEBs1 conjugation to sustain lethal envelope damage caused by active conjugation machinery. Conjugative elements must bypass the cell wall of both the donor and recipient cells in a mating pair. Conjugative elements encode cell wall hydrolases that are required for efficient transfer, which are presumed to partly degrade the cell wall of the donor bacterium during conjugation. In order to investigate the role of the ICEBs1-encoded cell wall hydrolase CwlT in conjugation, I generated cell wall-less (L-form) strains of B. subtilis which could donate or receive ICEBs1. In the absence of either the donor or recipient cell wall, CwlT was dispensable for efficient transfer. This finding indicates that CwlT acts on both the donor and recipient cell wall in a mating pair.
Author: Emily Lauryn Clark
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
Integrative and conjugative elements (ICEs) are widespread mobile genetic elements that facilitate the spread of many important genes, including those involved in antibiotic resistance, metabolism, pathogenesis, or symbiosis. These elements are also powerful tools for genetic analyses and engineering. ICEs are typically found integrated in a host chromosome. Either stochastically, or upon some signal, they can excise, undergo DNA processing events, be transferred through encoded conjugation machinery into a neighboring cell, and stably integrate into the new chromosome. Interactions between an ICE and its hosts throughout the life cycle can influence the efficiency of acquisition by new hosts. In this work, I investigated and compared the interactions that two ICEs, Tn916 and ICEBs1, have with their host cells. First, I explored how the different functional modules of these elements impact how efficiently they are transferred into different host species. I generated hybrid conjugative elements that merge functions of both elements to increase transfer efficiencies, presenting exciting potential to be used for genetic engineering. Next, I investigated a previously unknown ability of Tn916 to cause a growth arrest and kill its host cell. I took genetic approaches to determine that two Tn916-encoded genes interact with a defective phage-like element in the B. subtilis chromosome to elicit some of these effects. Finally, I evaluated the integration site selection of Tn916 in the B. subtilis chromosome, identifying several hundred unique AT-rich insertion sites, one of which is a "hot spot" for integration. I found that a host nucleoid-associated protein does not influence integration site selection. I conclude this body of work with a discussion of how the efficient spread of an element is shaped by its interactions with host cells and other horizontally acquired elements
Author: Adam P. Roberts
Publisher: CRC Press
ISBN: 1000724700
Category : Science
Languages : en
Pages : 456
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Book Description
As our understanding of mobile genetic elements continues to grow we are gaining a deeper appreciation of their importance in shaping the bacterial genome and in the properties they confer to their bacterial hosts. These include, but are by no means limited to, resistance to antibiotics, and heavy metals, toxin production and increased virulence, production of antibiotics and the ability to utilize a diverse range of metabolic substrates. We are also gaining an understanding of diversity of these elements and their interactions with each other; a property which continually complicates any attempt to classify them. We are learning more about the molecular mechanisms by which they translocate to new genomic sites both within genomes and between different bacteria. This book provides a timely, state of the art update on the properties of an important selection of different bacterial integrative mobile genetic elements and the myriad of different ways in which they move and influence the biology of the host bacterium. The chapters are all written by authors who have undertaken pioneering work in their respective fields, making this book vital reading for all who are interested in the biology of bacteria and the mobile elements they carry.
Author: Laurel D. Wright
Publisher:
ISBN:
Category :
Languages : en
Pages : 136
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Book Description
Mobile genetic elements facilitate movement of genes, including those conferring antibiotic resistance and other traits, between bacteria. Integrative and conjugative elements (ICEs), also known as conjugative transposons, are a large family of mobile genetic elements that can transfer between neighboring cells. ICEs are found integrated in the chromosome of their host bacterium, where they are transmitted to daughter cells by chromosomal replication and cell division. Under certain conditions, ICE DNA will excise and form a circular plasmid-like intermediate. It was previously thought that ICEs were incapable of autonomous replication. However, my research, along with the work of others, shows that ICEs can replicate autonomously, and that many ICEs utilize a rolling circle replication mechanism. Plasmids and phages that use rolling circle replication encode a single strand origin (sso) that enhances priming of DNA synthesis. We identified a functional single strand origin, sso1, in the integrative and conjugative element ICEBs1 of Bacillus subtilis. Genetic analyses indicated that ICEBs1 uses sso1 and at least one other region for second strand DNA synthesis. Sso activity was important for autonomous, rolling circle replication of ICEBs1 in host cells, and for stable acquisition of the element in new host cells. I also showed that the broad-host range ICE Tn916 replicates autonomously by a rolling circle mechanism. Replication of Tn916 was dependent on the relaxase encoded by Tn916 orf20. The origin of transfer of Tn916, oriT(916), also functioned as an origin of replication. I found that the relaxase (Orf20) and the two putative helicase processivity factors (Orf22 and Orf23) encoded by Tn916 likely interact in a complex to facilitate replication. Lastly, I identified a functional single strand origin of replication (sso) in Tn916 that I predict primes second strand synthesis during rolling circle replication. The importance of autonomous replication by rolling circle in the ICE lifecycle and horizontal gene transfer processes is discussed.
Author: Günter Kahl
Publisher:
ISBN:
Category : Nature
Languages : en
Pages : 656
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Book Description
Author: Christopher M. Thomas
Publisher: CRC Press
ISBN: 0203304330
Category : Science
Languages : en
Pages : 459
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Book Description
Bacteria are the most ubiquitous of all organisms. Responsible for a number of diseases and for many of the chemical cycles on which life depends, they are genetically adaptable. Vital to this adaptability is the existence of autonomous genetic elements-plasmids-which promote genetic exchange and recombination. The genes carried by any particular plasmid may be found in only a few individuals of any species but can also be shared with other species and thus constitute a horizontal gene pool. This book explains the various contributions that plasmids make to this pool: the replication, stable inheritance and transfer modules, the phenotypic markers they carry, the way they evolve, the ways they contribute to their host population and the approaches that we use to study and classify them. It also looks at what we know about their activity in natural communities and the way that they interact with other mobile elements to promote bacterial evolution.
Author: Hervé Tettelin
Publisher: Springer Nature
ISBN: 3030382818
Category : Science
Languages : en
Pages : 311
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Book Description
This open access book offers the first comprehensive account of the pan-genome concept and its manifold implications. The realization that the genetic repertoire of a biological species always encompasses more than the genome of each individual is one of the earliest examples of big data in biology that opened biology to the unbounded. The study of genetic variation observed within a species challenges existing views and has profound consequences for our understanding of the fundamental mechanisms underpinning bacterial biology and evolution. The underlying rationale extends well beyond the initial prokaryotic focus to all kingdoms of life and evolves into similar concepts for metagenomes, phenomes and epigenomes. The book’s respective chapters address a range of topics, from the serendipitous emergence of the pan-genome concept and its impacts on the fields of microbiology, vaccinology and antimicrobial resistance, to the study of microbial communities, bioinformatic applications and mathematical models that tie in with complex systems and economic theory. Given its scope, the book will appeal to a broad readership interested in population dynamics, evolutionary biology and genomics.
Author: Stuart B. Levy
Publisher: McGraw-Hill Companies
ISBN:
Category : Science
Languages : en
Pages : 458
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Book Description
Author: Michael Chandler
Publisher: John Wiley & Sons
ISBN: 1555819214
Category : Science
Languages : en
Pages : 1321
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Book Description
An exploration of the raw power of genetic material to refashion itself to any purpose... Virtually all organisms contain multiple mobile DNAs that can move from place to place, and in some organisms, mobile DNA elements make up a significant portion of the genome. Mobile DNA III provides a comprehensive review of recent research, including findings suggesting the important role that mobile elements play in genome evolution and stability. Editor-in-Chief Nancy L. Craig assembled a team of multidisciplinary experts to develop this cutting-edge resource that covers the specific molecular mechanisms involved in recombination, including a detailed structural analysis of the enzymes responsible presents a detailed account of the many different recombination systems that can rearrange genomes examines the tremendous impact of mobile DNA in virtually all organisms Mobile DNA III is valuable as an in-depth supplemental reading for upper level life sciences students and as a reference for investigators exploring new biological systems. Biomedical researchers will find documentation of recent advances in understanding immune-antigen conflict between host and pathogen. It introduces biotechnicians to amazing tools for in vivo control of designer DNAs. It allows specialists to pick and choose advanced reviews of specific elements and to be drawn in by unexpected parallels and contrasts among the elements in diverse organisms. Mobile DNA III provides the most lucid reviews of these complex topics available anywhere.
Author: Frans J. de Bruijn
Publisher: John Wiley & Sons
ISBN: 1119004896
Category : Science
Languages : en
Pages : 1472
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Book Description
Bacteria in various habitats are subject to continuously changing environmental conditions, such as nutrient deprivation, heat and cold stress, UV radiation, oxidative stress, dessication, acid stress, nitrosative stress, cell envelope stress, heavy metal exposure, osmotic stress, and others. In order to survive, they have to respond to these conditions by adapting their physiology through sometimes drastic changes in gene expression. In addition they may adapt by changing their morphology, forming biofilms, fruiting bodies or spores, filaments, Viable But Not Culturable (VBNC) cells or moving away from stress compounds via chemotaxis. Changes in gene expression constitute the main component of the bacterial response to stress and environmental changes, and involve a myriad of different mechanisms, including (alternative) sigma factors, bi- or tri-component regulatory systems, small non-coding RNA’s, chaperones, CHRIS-Cas systems, DNA repair, toxin-antitoxin systems, the stringent response, efflux pumps, alarmones, and modulation of the cell envelope or membranes, to name a few. Many regulatory elements are conserved in different bacteria; however there are endless variations on the theme and novel elements of gene regulation in bacteria inhabiting particular environments are constantly being discovered. Especially in (pathogenic) bacteria colonizing the human body a plethora of bacterial responses to innate stresses such as pH, reactive nitrogen and oxygen species and antibiotic stress are being described. An attempt is made to not only cover model systems but give a broad overview of the stress-responsive regulatory systems in a variety of bacteria, including medically important bacteria, where elucidation of certain aspects of these systems could lead to treatment strategies of the pathogens. Many of the regulatory systems being uncovered are specific, but there is also considerable “cross-talk” between different circuits. Stress and Environmental Regulation of Gene Expression and Adaptation in Bacteria is a comprehensive two-volume work bringing together both review and original research articles on key topics in stress and environmental control of gene expression in bacteria. Volume One contains key overview chapters, as well as content on one/two/three component regulatory systems and stress responses, sigma factors and stress responses, small non-coding RNAs and stress responses, toxin-antitoxin systems and stress responses, stringent response to stress, responses to UV irradiation, SOS and double stranded systems repair systems and stress, adaptation to both oxidative and osmotic stress, and desiccation tolerance and drought stress. Volume Two covers heat shock responses, chaperonins and stress, cold shock responses, adaptation to acid stress, nitrosative stress, and envelope stress, as well as iron homeostasis, metal resistance, quorum sensing, chemotaxis and biofilm formation, and viable but not culturable (VBNC) cells. Covering the full breadth of current stress and environmental control of gene expression studies and expanding it towards future advances in the field, these two volumes are a one-stop reference for (non) medical molecular geneticists interested in gene regulation under stress.
