Cholera Toxin (CT): Organization and Function of the Relevant Genetic Elements

2009 ◽  
pp. 125-145
Keyword(s):  
Cholera Toxin ◽  
Genetic Elements ◽  
And Function

scholarly journals Resurgent Vibrio cholerae O139: Rearrangement of Cholera Toxin Genetic Elements and Amplification ofrrn Operon

1999 ◽  
Vol 67 (1) ◽  
pp. 148-154 ◽  
Author(s):  
Gopal Khetawat ◽  
Rupak K. Bhadra ◽  
Suvobroto Nandi ◽  
Jyotirmoy Das
Keyword(s):  
Cholera Toxin ◽  
Vibrio Cholerae ◽  
Indian Subcontinent ◽  
Antibiotic Sensitivity ◽  
Direct Repeat ◽  
Phenotypic Traits ◽  
Genetic Elements ◽  
Restriction Sites ◽  
Vibrio Cholerae O139 ◽  
El Tor

ABSTRACT The unprecedented genesis of a novel non-O1 Vibrio cholerae strain belonging to serogroup O139, which caused an epidemic in late 1992 in the Indian subcontinent, and its subsequent displacement by El Tor O1 vibrios after 18 months initiated a renewed investigation of the aspects of the organism that are related to pathogenesis. The reappearance of V. cholerae O139 with altered antibiotic sensitivity compared to O139 Bengal (O139B) in late 1996 has complicated the epidemiological scenario of V. cholerae and has necessitated an examination of possible rearrangements in the genome underlying such rapid changes in the phenotypic traits. With a view to investigating whether the phenotypic changes that have occurred are associated with alteration in the genome, the genome of the resurgent V. cholerae O139 (O139R) strains were examined. Pulsed-field gel electrophoresis analysis of NotI- and SfiI-digested genomic DNA of O139R isolates showed restriction fragment length polymorphism including in the cholera toxin (CTX) genetic element locus and with O139B isolates. Analyses of the organization of the CTX genetic elements in O139R strains showed that in contrast to two copies of the elements connected by two direct-repeat sequences (RS) in most of the genomes of O139B isolates, the genomes of all O139R strains examined, except strain AS192, have three such elements connected by a single RS. While the RS present in the upstream of the CTX genetic elements in the genome of O139R is of O139B origin, the RS connecting the cores of the elements has several new restriction sites and has lost theBglII site which is supposed to be conserved in all O1 strains and O139B. The endonuclease I-CeuI, which has sites only in the rrn operons in the genomes of all organisms examined so far, has 10 sites in the genomes of O139R strains, compared to 9 in the genomes of O139B strains. The recent isolates of V. cholerae O139 have thus gained one rrn operon. This variation in the number of rrn operons within a serogroup has not been reported for any other organism. The results presented in this report suggest that like the pathogenic El Tor O1 strains, the genomes of O139 strains are undergoing rapid alterations.

scholarly journals CRISPR-Cas systems are widespread accessory elements across bacterial and archaeal plasmids

2021 ◽  
Author(s):  
Rafael Pinilla-Redondo ◽  
Jakob Russel ◽  
David Mayo-Muñoz ◽  
Shiraz A Shah ◽  
Roger A Garrett ◽  
...  
Keyword(s):  
Mobile Genetic Elements ◽  
Comprehensive Analysis ◽  
Immune Protection ◽  
Genetic Elements ◽  
And Function

Abstract Many prokaryotes encode CRISPR-Cas systems as immune protection against mobile genetic elements (MGEs), yet a number of MGEs also harbor CRISPR-Cas components. With a few exceptions, CRISPR-Cas loci encoded on MGEs are uncharted and a comprehensive analysis of their distribution, prevalence, diversity, and function is lacking. Here, we systematically investigated CRISPR-Cas loci across the largest curated collection of natural bacterial and archaeal plasmids. CRISPR-Cas loci are widely but heterogeneously distributed across plasmids and, in comparison to host chromosomes, their mean prevalence per Mbp is higher and their distribution is distinct. Furthermore, the spacer content of plasmid CRISPRs exhibits a strong targeting bias towards other plasmids, while chromosomal arrays are enriched with virus-targeting spacers. These contrasting targeting preferences highlight the genetic independence of plasmids and suggest a major role for mediating plasmid-plasmid conflicts. Altogether, CRISPR-Cas are frequent accessory components of many plasmids, which is an overlooked phenomenon that possibly facilitates their dissemination across microbiomes.

scholarly journals The role of antigen form and function in the primary and secondary intestinal immune responses to cholera toxin and toxoid in rats

1978 ◽  
Vol 148 (1) ◽  
pp. 195-206 ◽  
Author(s):  
NF Pierce
Keyword(s):  
Single Dose ◽  
Immune Responses ◽  
Cholera Toxin ◽  
Cell Membranes ◽  
Primary Response ◽  
Adenyl Cyclase ◽  
Systemic Immune Response ◽  
Form And Function ◽  
And Function

This report describes studies of the mucosal antitoxic response in rats after enteric administration of several forms of cholera toxin or toxoid, proteins which differ primarily in their ability to bind to cell membranes and activate cellular adenyl cyclase. These two characteristics appeared to markedly enhance the local primary response to these antigens. A single dose of toxoid lacking these features was ineffective in local priming even though it was absorbed and induced a systemic immune response. Single dose mucosal priming occurred only with preparations which bind to cell membranes and was enhanced by those which also activate cellular adenyl cyclase. In contrast, single-dose mucosal boosting was best accomplished by materials with these properties but was also seen with a toxoid lacking both of these functions. The property of membrane binding appears to be most advantageous in mucosal priming, perhaps by increasing effective trapping of absorbed antigen in unprimed mucosal lymphoid tissue, whereas the ability to activate adenyl cyclase appears to enhance primary and secondary type responses about equally. Combinations of crude toxoid and toxin were also more effective in mucosal priming than purified materials, a finding which is unexplained. A single dose of this combination induced mucosal priming which was fully developed in 2 wk, undiminished after 4 too, and only modestly diminished after 8 mo, thus demonstrating relatively prolonged memory in the IgA mucosal immune system. Effective two-dose local immunizing regimens were developed, and it was shown that there was no correlation between the mucosal and systemic secondary antitoxin responses provoked by these regimens.

scholarly journals Bioinformatics and Machine Learning Approaches to Understand the Regulation of Mobile Genetic Elements

Biology ◽  
2021 ◽  
Vol 10 (9) ◽  
pp. 896
Author(s):  
Ilektra-Chara Giassa ◽  
Panagiotis Alexiou
Keyword(s):  
Machine Learning ◽  
Chromatin Modification ◽  
Mobile Genetic Elements ◽  
Learning Approaches ◽  
Sequencing Data ◽  
Methylation Analysis ◽  
Developmental Defects ◽  
Genetic Elements ◽  
Bisulfite Sequencing Data ◽  
And Function

Transposable elements (TEs, or mobile genetic elements, MGEs) are ubiquitous genetic elements that make up a substantial proportion of the genome of many species. The recent growing interest in understanding the evolution and function of TEs has revealed that TEs play a dual role in genome evolution, development, disease, and drug resistance. Cells regulate TE expression against uncontrolled activity that can lead to developmental defects and disease, using multiple strategies, such as DNA chemical modification, small RNA (sRNA) silencing, chromatin modification, as well as sequence-specific repressors. Advancements in bioinformatics and machine learning approaches are increasingly contributing to the analysis of the regulation mechanisms. A plethora of tools and machine learning approaches have been developed for prediction, annotation, and expression profiling of sRNAs, for methylation analysis of TEs, as well as for genome-wide methylation analysis through bisulfite sequencing data. In this review, we provide a guided overview of the bioinformatic and machine learning state of the art of fields closely associated with TE regulation and function.

Structure and function of cholera toxin and hormone receptors

1976 ◽  
Vol 4 (1) ◽  
pp. 99-120 ◽  
Author(s):  
V. Bennett ◽  
S. Craig ◽  
M. D. Hollenberg ◽  
E. O'Keefe ◽  
N. Sahyoun ◽  
...  
Keyword(s):  
Cholera Toxin ◽  
Hormone Receptors ◽  
Structure And Function ◽  
And Function
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