scholarly journals Phase variable expression of pdcB, a phosphodiesterase influences sporulation in Clostridioides difficile

2021 ◽  
Author(s):  
Revathi Govind ◽  
Babita Adhikari Dhungel
Keyword(s):  
Developed Countries ◽  
Upstream Region ◽  
Phase Variable ◽  
Global Regulators ◽  
Dna Inversion ◽  
Variable Expression ◽  
Clostridioides Difficile ◽  
Biochemical Assays ◽  
Antibiotic Associated Diarrhea ◽  
The Right

Clostridioides difficile is the causative agent of antibiotic-associated diarrhea and is the leading cause of nosocomial infection in developed countries. An increasing number of C. difficile infections are attributed to hypervirulence strains that produce more toxins and spores. C. difficile spores are the major factor for the transmission and persistence of the organism. Previous studies have identified global regulators that influence sporulation in C. difficile. This study discovered that PdcB, a phosphodiesterase to influence sporulation in C. difficile UK1 strain positively. Through genetic and biochemical assays, we have shown that phase variable expression of pdcB results in hypo- and hyper-sporulation phenotype. In the ON orientation, the identified promotor is the right orientation to drive the expression of pdcB. Production of PdcB phosphodiesterase reduces the intracellular cyclic-di-GMP concentration, resulting in hyper-sporulation phenotype. The OFF orientation of pdcB switch or mutating pdcB results in increased cyclic-di-GMP and hypo-sporulating phenotype. Additionally, we demonstrated that CodY binds to the upstream region of pdcB to represses its expression, and CodY mediated repression is relieved by the DNA inversion.

scholarly journals Local and Global Regulators Linking Anaerobiosis to cupA Fimbrial Gene Expression in Pseudomonas aeruginosa

2007 ◽  
Vol 189 (23) ◽  
pp. 8667-8676 ◽  
Author(s):  
Isabelle Vallet-Gely ◽  
Josh S. Sharp ◽  
Simon L. Dove
Keyword(s):  
Gene Expression ◽  
Pseudomonas Aeruginosa ◽  
Opportunistic Pathogen ◽  
Phase Variable ◽  
Global Regulators ◽  
Variable Expression ◽  
Regulatory Cascade ◽  
Abiotic Surfaces ◽  
Positive Regulators ◽  
Anaerobic Environment

ABSTRACT The cupA gene cluster of Pseudomonas aeruginosa encodes components and assembly factors of a putative fimbrial structure that enable this opportunistic pathogen to form biofilms on abiotic surfaces. In P. aeruginosa the control of cupA gene expression is complex, with the H-NS-like MvaT protein functioning to repress phase-variable (on/off) expression of the operon. Here we identify four positive regulators of cupA gene expression, including three unusual regulators encoded by the cgrABC genes and Anr, a global regulator of anaerobic gene expression. We show that the cupA genes are expressed in a phase-variable manner under anaerobic conditions and that the cgr genes are essential for this expression. We show further that cgr gene expression is negatively controlled by MvaT and positively controlled by Anr and anaerobiosis. Expression of the cupA genes therefore appears to involve a regulatory cascade in which anaerobiosis, signaled through Anr, stimulates expression of the cgr genes, resulting in a concomitant increase in cupA gene expression. Our findings thus provide mechanistic insight into the regulation of cupA gene expression and identify anaerobiosis as an inducer of phase-variable cupA gene expression, raising the possibility that phase-variable expression of fimbrial genes important for biofilm formation may occur in P. aeruginosa persisting in the largely anaerobic environment of the cystic fibrosis host lung.

scholarly journals Variable Lipoprotein Genes of Mycoplasma agalactiae Are Activated In Vivo by Promoter Addition via Site-Specific DNA Inversions

2003 ◽  
Vol 71 (7) ◽  
pp. 3821-3830 ◽  
Author(s):  
Ravenna Flitman-Tene ◽  
Sigalit Mudahi-Orenstein ◽  
Sharon Levisohn ◽  
David Yogev
Keyword(s):  
Dna Recombination ◽  
Small Ruminants ◽  
Upstream Region ◽  
Pcr Analysis ◽  
Phase Variable ◽  
Multiple Sequence ◽  
Site Specific ◽  
Mycoplasma Agalactiae ◽  
Variable Expression

ABSTRACT Mycoplasma agalactiae, the etiological agent of contagious agalactia of small ruminants, has a family of related genes (avg genes) which encode surface lipoprotein antigens that undergo phase variation. A series of 13 M. agalactiae clonal isolates, obtained from one chronically infected animal over a period of 7 months, were found to undergo major rearrangement events within the avg genomic locus. We show that these rearrangements regulate the phase-variable expression of individual avg genes. Northern blot analysis and reverse transcription-PCR showed that only one avg gene is transcribed, while the other avg genes are transcriptionally silent. Sequence analysis and primer extension experiments with two M. agalactiae clonal isolates showed that a specific 182-bp avg 5′ upstream region (avg-B2) that is present as a single chromosomal copy serves as an active promoter and exhibits a high level of homology with the vsp promoter of the bovine pathogen Mycoplasma bovis. PCR analysis showed that each avg gene is associated with the avg-B2 promoter in a subpopulation of cells that is present in each subclone. Multiple sequence-specific sites for DNA recombination (vis-like), which are presumably recognized by site-specific recombinase, were identified within the conserved avg 5′ upstream regions of all avg genes and were found to be identical to the recombination sites of the M. bovis vsp locus. In addition, a gene encoding a member of the integrase family of tyrosine site-specific recombinases was identified adjacent to the variable avg locus. The molecular genetic basis for avg phase-variable expression appears to be mediated by site-specific DNA inversions occurring in vivo that allow activation of a silent avg gene by promoter addition. A model for the control of avg genes is proposed.

Experiences in Water Resources Management in Developed Regions

1987 ◽  
Vol 19 (9) ◽  
pp. 217-223
Author(s):  
Leo Weaver ◽  
Peter A. Tennant
Keyword(s):  
Water Resources ◽  
Water Resources Management ◽  
Engineering Application ◽  
Resource Planning ◽  
Developed Countries ◽  
Historical Background ◽  
Science And Engineering ◽  
Resources Management ◽  
Quality Of Water ◽  
The Right

The science and engineering of water resources in developed countries has undergone profound changes in less than a professional lifetime. This has radically influenced education and research and essentially revolutionized water resource planning. Fundamental uses of water to fulfill society's needs continue. These include domestic and industrial supplies, waterways for transport, fire protection, waste carriage, recreation, irrigation, and in general, an adequate quantity and quality of water in the right place at the right time to fulfill human and aquatic needs. The complexities of water resources no longer may be measured largely in terms of science and engineering challenges alone, but must include economics sensitive to the political and social sciences. What has evolved is what is now best described as water management. This paper reviews the evolvement of water resources management in developed counties in terms of historical background, and national policies and institutions, particularly as this evolvement impacts scientific research and engineering application.

scholarly journals GAA Trinucleotide Repeat Region Regulates M9/pMGA Gene Expression in Mycoplasma gallisepticum

2000 ◽  
Vol 68 (2) ◽  
pp. 871-876 ◽  
Author(s):  
Li Liu ◽  
Kevin Dybvig ◽  
Victor S. Panangala ◽  
Vicky L. van Santen ◽  
Christopher T. French
Keyword(s):  
Gene Expression ◽  
Trinucleotide Repeat ◽  
Mycoplasma Gallisepticum ◽  
Avian Host ◽  
Phase Variable ◽  
Repeat Region ◽  
Chromosomal Dna ◽  
Promoter Regions ◽  
Variable Expression ◽  
Gaa Repeats

ABSTRACT Mycoplasma gallisepticum, the cause of chronic respiratory infections in the avian host, possesses a family of M9/pMGA genes encoding an adhesin(s) associated with hemagglutination. Nucleotide sequences of M9/pMGA gene family members indicate extensive sequence similarity in the promoter regions of both the transcribed and silent genes. The mechanism that regulates M9/pMGA gene expression is unknown, but studies have revealed an apparent correlation between gene expression and the number of tandem GAA repeat motifs located upstream of the putative promoter. In this study, transposon Tn4001was used as a vector with the Escherichia coli lacZ gene as the reporter system to examine the role of the GAA repeats in M9/pMGA gene expression in M. gallisepticum. A 336-bp M9 gene fragment (containing the GAA repeat region, the promoter, and the translation start codon) was amplified by PCR, ligated with alacZ gene from E. coli, and inserted into the Tn4001-containing plasmid pISM2062. This construct was transformed into M. gallisepticum PG31. Transformants were filter cloned on agar supplemented with 5-bromo-4-chloro-3-indolyl-β-d-galactopyranoside (X-Gal) to monitor lacZ gene expression on the basis of blue/white color selection. Several cycles of filter cloning resulted in cell lineages in which lacZ gene expression alternated between the On and Off states in successive generations of progeny clones. The promoter regions of the M9-lacZ hybrid genes of individual progeny clones were amplified by PCR and sequenced. The only differences between the promoter regions of the blue and white colonies were in the number of GAA repeats. Clones that expressedlacZ had exactly 12 tandem copies of the GAA repeat. Clones that did not express lacZ invariably had either more than 12 (14 to 16) or fewer than 12 (5 to 11) GAA repeats. Southern analysis of M. gallisepticum chromosomal DNA confirmed that the phase-variable expression of the lacZ reporter gene was not caused by Tn4001 transposition. These data strongly indicate that changes in the length of the GAA repeat region are responsible for regulating M9/pMGA gene expression.

scholarly journals Spo0A Suppresses sin Locus Expression in Clostridioides difficile

mSphere ◽  
2020 ◽  
Vol 5 (6) ◽  
Author(s):  
Babita Adhikari Dhungel ◽  
Revathi Govind
Keyword(s):  
Diarrheal Disease ◽  
Toxin Production ◽  
The United States ◽  
Upstream Region ◽  
Pcr Analysis ◽  
Bacterial Cells ◽  
Master Regulator ◽  
Content Type ◽  
Clostridioides Difficile

ABSTRACT Clostridioides difficile is the leading cause of nosocomial infection and is the causative agent of antibiotic-associated diarrhea. The severity of the disease is directly associated with toxin production, and spores are responsible for the transmission and persistence of the organism. Previously, we characterized sin locus regulators SinR and SinR′ (we renamed it SinI), where SinR is the regulator of toxin production and sporulation. The SinI regulator acts as its antagonist. In Bacillus subtilis, Spo0A, the master regulator of sporulation, controls SinR by regulating the expression of its antagonist, sinI. However, the role of Spo0A in the expression of sinR and sinI in C. difficile had not yet been reported. In this study, we tested spo0A mutants in three different C. difficile strains, R20291, UK1, and JIR8094, to understand the role of Spo0A in sin locus expression. Western blot analysis revealed that spo0A mutants had increased SinR levels. Quantitative reverse transcription-PCR (qRT-PCR) analysis of its expression further supported these data. By carrying out genetic and biochemical assays, we show that Spo0A can bind to the upstream region of this locus to regulates its expression. This study provides vital information that Spo0A regulates the sin locus, which controls critical pathogenic traits such as sporulation, toxin production, and motility in C. difficile. IMPORTANCE Clostridioides difficile is the leading cause of antibiotic-associated diarrheal disease in the United States. During infection, C. difficile spores germinate, and the vegetative bacterial cells produce toxins that damage host tissue. In C. difficile, the sin locus is known to regulate both sporulation and toxin production. In this study, we show that Spo0A, the master regulator of sporulation, controls sin locus expression. Results from our study suggest that Spo0A directly regulates the expression of this locus by binding to its upstream DNA region. This observation adds new detail to the gene regulatory network that connects sporulation and toxin production in this pathogen.

scholarly journals Proteomic Adaptation of Clostridioides difficile to Treatment with the Antimicrobial Peptide Nisin

Cells ◽  
2021 ◽  
Vol 10 (2) ◽  
pp. 372
Author(s):  
Sandra Maaß ◽  
Jürgen Bartel ◽  
Pierre-Alexander Mücke ◽  
Rabea Schlüter ◽  
Thomas Sura ◽  
...  
Keyword(s):  
State Of The Art ◽  
Biomedical Application ◽  
Time Resolved ◽  
Antibiotic Resistant ◽  
Cellular Processes ◽  
Clostridioides Difficile ◽  
Antibiotic Associated Diarrhea ◽  
Life Threatening ◽  
Sublethal Concentrations ◽  
Interesting Alternative

Clostridioides difficile is the leading cause of antibiotic-associated diarrhea but can also result in more serious, life-threatening conditions. The incidence of C. difficile infections in hospitals is increasing, both in frequency and severity, and antibiotic-resistant C. difficile strains are advancing. Against this background antimicrobial peptides (AMPs) are an interesting alternative to classic antibiotics. Information on the effects of AMPs on C. difficile will not only enhance the knowledge for possible biomedical application but may also provide insights into mechanisms of C. difficile to adapt or counteract AMPs. This study applies state-of-the-art mass spectrometry methods to quantitatively investigate the proteomic response of C. difficile 630∆erm to sublethal concentrations of the AMP nisin allowing to follow the cellular stress adaptation in a time-resolved manner. The results do not only point at a heavy reorganization of the cellular envelope but also resulted in pronounced changes in central cellular processes such as carbohydrate metabolism. Further, the number of flagella per cell was increased during the adaptation process. The potential involvement of flagella in nisin adaptation was supported by a more resistant phenotype exhibited by a non-motile but hyper-flagellated mutant.

scholarly journals Clostridioides difficile Infection, Still a Long Way to Go

2021 ◽  
Vol 10 (3) ◽  
pp. 389
Author(s):  
Eleftheria Kampouri ◽  
Antony Croxatto ◽  
Guy Prod’hom ◽  
Benoit Guery
Keyword(s):  
Fecal Microbiota Transplantation ◽  
Diagnostic Algorithm ◽  
Fecal Microbiota ◽  
Diagnostic Methods ◽  
Special Focus ◽  
Surveillance Systems ◽  
Main Question ◽  
Clostridioides Difficile ◽  
Clostridioides Difficile Infection ◽  
The Right

Clostridioides difficile is an increasingly common pathogen both within and outside the hospital and is responsible for a large clinical spectrum from asymptomatic carriage to complicated infection associated with a high mortality. While diagnostic methods have considerably progressed over the years, the optimal diagnostic algorithm is still debated and there is no single diagnostic test that can be used as a standalone test. More importantly, the heterogeneity in diagnostic practices between centers along with the lack of robust surveillance systems in all countries and an important degree of underdiagnosis due to lack of clinical suspicion in the community, hinder a more accurate evaluation of the burden of disease. Our improved understanding of the physiopathology of CDI has allowed some significant progress in the treatment of CDI, including a broader use of fidaxomicine, the use of fecal microbiota transplantation for multiples recurrences and newer approaches including antibodies, vaccines and new molecules, already developed or in the pipeline. However, the management of CDI recurrences and severe infections remain challenging and the main question remains: how to best target these often expensive treatments to the right population. In this review we discuss current diagnostic approaches, treatment and potential prevention strategies, with a special focus on recent advances in the field as well as areas of uncertainty and unmet needs and how to address them.

RIGHT OF ACTION TO CHALLENGE TRANSACTIONS THAT RESULT IN FOREIGN INVESTORS GAINING CONTROL OVER BUSINESS ENTITIES OF STRATEGIC IMPORTANCE

2021 ◽  
Vol 11 (4) ◽  
pp. 112-138
Author(s):  
D.A. FEDYAEV
Keyword(s):  
Public Interest ◽  
Developed Countries ◽  
Foreign Investor ◽  
Foreign Investors ◽  
The Public ◽  
Right Of Action ◽  
Judicial Proceedings ◽  
The Law ◽  
Business Entities ◽  
The Right

In the Russian Federation, as in a number of other economically developed countries, there are legal restrictions on the admission of foreign investors to participate in commercial corporate organizations of strategic importance for national defence and state security. Failure by foreign investors to comply with this mechanism leads to the nullity of transactions and, as a consequence, to legal disputes, the subject of which are mainly restitution claims. There have been numerous problems and academic debates in recent court practice regarding the reasons and the possibility of satisfying such claims. In particular, in view of the changed circumstances after the conclusion of the contested transaction, the real public interest is not always visible pursued by the claim for application of consequences of its invalidity. The author proposes that in the course of judicial proceedings in such cases, when the defendant raises the relevant reasoned objections, not only to state the fact of violation of the law by a foreign investor, but also to reveal the public interest defended by the foreign investor. The author proposes that, in such cases, the defendant’s arguments should not be limited to stating that the foreign investor has breached the law. If one is not established, a claim may be dismissed under certain conditions, taking into account established doctrinal approaches to the understanding of the right of action.

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