Amit Ghosh

• Ph.D
• Professor Emeritus at National Institute of Cholera and Enteric Diseases

Antimicrobial resistance (AMR) in bacteria is an important global health problem affecting humans, animals, and the environment. AMR is considered as one of the major components in the “global one health”. Misuse/overuse of antibiotics in any one of the segments can impact the integrity of the others. In the presence of antibiotic selective pressur...

Non-typhoidal Salmonella serotypes are well-adapted to utilize the inflammation for colonization in mammalian gut mucosa and bring down the integrity of the epithelial barrier in mammalian intestine. The present study...

Diarrheal disease remains a great public health problem in many countries. Enteric infections caused by several viral, bacterial and parasitic species not only affect the host, but also alter the gut microbiome. The host physiology dictates the intestinal milieu and decides the composition and richness of gut microbiota, which forms a homeostatic e...

Aims: The present study aimed to document the comparative analysis of differential hyper-virulent features of Vibrio cholerae O1 strains isolated during 2018 from cholera endemic regions in Gujarat and Maharashtra (Western India) and West Bengal (Eastern India). Methods and results: A total of 87 V. cholerae O1 clinical strains from Western Indi...

Cholera is a life-threatening infectious disease that remains an important public health issue in several low and middle-income countries. In 1992, a newly identified O139 Vibrio cholerae temporarily displaced the O1 serogroup. No study has been able to answer why the potential eighth cholera pandemic (8CP) causing V. cholerae O139 emerged so succe...

A complex virulence regulatory cascade controls expression of the cholera toxin genes (ctxAB) in Vibrio cholerae; which eventually leads to the production and secretion of choleragen (CT), responsible for rice watery diarrhoea in infected individuals. The cholera toxin promoter (PctxAB) contains a series of heptad repeats (5′-TTTTGAT-3′); which has...

A complex regulatory cascade controls expression of the cholera toxin genes ( ctxAB ) in Vibrio cholerae ; which eventually leads to choleragen (CT) production and secretion, resulting in rice watery diarrhoea. The cholera toxin promoter (P ctxAB ) contains a series of heptad repeats (5’-TTTTGAT-3’); which have been previously shown to play crucial...

Cholera affects about three million people annually and kills several thousands. Since 1817 seven cholera pandemics have been described. While the nature of the strains responsible for the first four pandemics are not known, the fifth and sixth pandemics are associated with Vibrio cholerae O1 classical biotype. In the 1960s, V. cholerae El Tor repl...

Helicobacter pylori, a type 1 carcinogen, accounts for numerous gastric cancer-related deaths worldwide. Repurposing existing drugs or developing new ones for a combinatorial approach against increasing antimicrobial resistance is the need of the hour. This study highlights the efficacy of acriflavine hydrochloride (ACF-HCl) in inhibiting the growt...

The endemicity of cholera in India has been well researched. Among the other endemic areas, Indian subcontinent appears to be the cradle of Vibrio cholerae genovariants, which subsequently spread worldwide. In contrast, all the cholera cases recorded in Russia are of imported origin. In the past century, such importations might result in epidemics,...

The human pathogen Vibrio cholerae is the causative agent of severe diarrheal disease known as cholera. Of the more than 200 “O” serogroups of this pathogen, O1 and O139 cause cholera outbreaks and epidemics. The rest of the serogroups, collectively known as non-O1/non-O139 cause sporadic moderate or mild diarrhea and also systemic infections. Path...

Antimicrobial peptides play an important role in host-defence against Vibrio cholerae . Generally, V. cholerae O1 classical biotype is polymyxin B (PB) sensitive and El Tor is relatively resistant. Detection of classical biotype traits like cholera toxin B-subunit gene ctxB1 and PB sensitivity in El Tor strains have been reported in recent years, i...

Cholera continues to be an important public health concern in developing countries where proper hygiene and sanitation are compromised. This severe diarrheal disease is caused by the Gram-negative pathogen Vibrio cholerae belonging to serogroups O1 and O139. Cholera toxin (CT) is the prime virulence factor and is directly responsible for the diseas...

The self-transferring integrative and conjugative elements (ICEs) are large genomic segments carrying several bacterial adaptive functions including antimicrobial resistance (AMR). SXT/R391 family is one of the ICEs extensively studied in cholera-causing pathogen Vibrio cholerae. The genetic characteristics of ICE-SXT/R391 in V. cholerae are dynami...

[This corrects the article DOI: 10.3389/fpubh.2019.00203.].

Toxigenic Vibrio cholerae is responsible for 1.4 to 4.3 million cases with about 21,000–143,000 deaths per year. Dominance of O1 and O139 serogroups, classical and El tor biotypes, alterations in CTX phages and the pathogenicity Islands are some of the major features of V. cholerae isolates that are responsible for cholera epidemics. Whole-genome s...

The unique genetic makeup and remarkable competency of Vibrio cholerae are the key factors that help the cholera pathogen adapt rapidly to adverse environmental conditions and resist the detrimental effect of antimicrobial agents. In the last few decades, V. cholerae that causes acute watery diarrhoeal disease cholera has emerged as a notorious mul...

The progressive rise in antibiotic resistance among enteric pathogens in developing countries is becoming a big concern. India is one of the largest consumers of antibiotics, and their use is not well regulated. V. fluvialis is increasingly recognized as an emerging diarrheal pathogen of public health importance. Here we report the emergence of azi...

Vibrio cholerae causes fatal diarrheal disease cholera in humans due to consumption of contaminated water and food. To instigate the disease, the bacterium must evade the host intestinal innate immune system; penetrate the mucus layer of the small intestine, adhere and multiply on the surface of microvilli and produce toxin(s) through the action of...

Carbapenems have been used for many years to treat severe nosocomial Enterobacteriaceae infections. The spread of resistance to these drugs among other bacterial families is an emerging problem worldwide, mostly caused by New Delhi metallo-β-lactamase (NDM-1). We screened for the prevalence of NDM-1-expressing enteric pathogens from hospitalized pa...

A carbapenem resistant Salmonella enterica serovar Senftenberg isolate BCH 2406 was isolated from a diarrheal child attending an outpatient unit of B.C. Roy Hospital in Kolkata, India. This isolate was positive for the blaNDM-1 in the PCR assay, which was confirmed by amplicon sequencing. Except for tetracycline, this isolate was resistant to all t...

Twenty seven Enterotoxigenic Bacteroides fragilis (ETBF) strains isolated from children in Kolkata, India, were tested for their antimicrobial resistance, presence of integrons and resistance encoding genes. Almost all the strains (>90%) were resistant to two or more antimicrobials. About 59 to 92% of the strains were resistant to ampicillin, amoxi...

New β-lactamases with ever-broadening substrate specificity are disseminating rapidly all over the world. In the recent years, extent of resistance of human pathogens to β-lactam antibiotics is increasing due to the emergence of "new" carbapenemase-producers. New Delhi metallo-β-lactamase (NDM) is the latest carbapenemasc, detected for the first ti...

Under stress conditions, many species of bacteria enter into starvation mode of metabolism or a physiologically viable but non-culturable (VBNC) state. Several human pathogenic bacteria have been reported to enter into the VBNC state under these conditions. The pathogenic VBNC bacteria cannot be grown using conventional culture media, although they...

Background: A live oral cholera vaccine VA 1.4 developed from a non-toxigenic Vibrio cholerae O1 El Tor strain using ctxB gene insertion was further developed into a clinical product following cGMP and was evaluated in a double-blind randomized placebo controlled parallel group two arm trial with allocation ratio of 1∶1 for safety and immunogenici...

Ability of a cocktail of five lytic vibriophages to combatting V. cholerae O1 infection in rabbit model was examined. In one group, rabbits were administered 1x10(8) plaque forming unit of phage cocktail 6 and 12 h prior to the administration of V. cholerae O1, while in the other group, same procedure was applied 6 and 12 h post infection. It was o...

Microorganisms are extraordinarily diverse in their range of habitats. They are capable of growing wherever life is thermodynamically possible, making them capable of synthesizing myriad varieties of molecules, compounds, enzymes etc, which are yet beyond the reach of human capabilities. Hence it is being increasingly appreciated that in the search...

Xylanases belong to an important class of industrial enzymes. Various xylanases have been purified and characterized from a plethora of organisms including bacteria, marine algae, plants, protozoans, insects, snails and crustaceans. Depending on the source, the enzymatic activity of xylanases varies considerably under various physico-chemical condi...

Resistance profiles and their correlation with genetic factors were investigated in 12 isolates of Vibrio fluvialis obtained from hospitalized patients in Kolkata, India, in 2006. All the strains displayed drug resistance with varying antibiograms. However, resistance to ampicillin and neomycin was common to all of them. Three isolates harboured pl...

Vibrio fluvialis, which causes cholera-like diarrhoea in humans, is one of the aetiological agents of acute diarrhoea in Kolkata, India, and is resistant to many antimicrobial agents. Two V. fluvialis isolates resistant to fluoroquinolones and β-lactam antimicrobials were found to have mutations in the quinolone resistance-determining regions (QRDR...

Diverse mechanisms have been identified in enteric bacteria for their adaptation and survival against multiple classes of antimicrobial agents. Resistance of bacteria to the most effective fluoroquinolones have increasingly been reported in many countries. We have identified that most of the enterotoxigenic Escherichia coli (ETEC) were resistant to...

In countries where cholera is endemic, Vibrio cholerae O1 bacteriophages have been detected in sewage water. These have been used to serve not only as strain markers, but also for the typing of V. cholerae strains. Vibriophage N4 (ATCC 51352-B1) occupies a unique position in the new phage-typing scheme and can infect a larger number of V. cholerae...

The synthesis of β-galactosidase (EC 3.2.1.23; β-D-galactoside galactohydrolase) in E. coli was repressed as a result of infection with single-stranded DNA phage . Evidence is presented to show that this repression was not due to the restricted entry of the inducer molecules into the infected cells but to some phage-specified product(s). It was fur...

Antimicrobial resistance poses a major threat in the treatment of infectious diseases. Though significant progress in the management of diarrhoeal diseases has been achieved by improved hygiene, development of new antimicrobials and vaccines, the burden remains the same, especially in children below 5 yr of age. In the case of cholera, though oral...

The disease cholera is the result of infection with the toxigenic strains of Vibrio cholerae. Even though the oral rehydration therapy is the main stay for the treatment of cholera patients, administration of antimicrobials is a common existing practice as it shortens the volume and duration of diarrhea, duration of hospitalization, and excretion o...

Multiple sequence alignments of the BSX with those of other GH10 xylanases of Bacillus origin. AAB70918: Bacillus sp. NG-27 (BSX), which is used in the present study, AAV98623: Bacillus halodurans S7 (BHX), AAQ83581: Bacillus firmus (BFX), CAA84631: Bacillus sp. N137, AAQ99279: Bacillus alcalophilus AX2000. Aromatic residues enclosed in rectangles...

Determination of Cm of R-BSX and its mutant by pulse proteolysis. We used 0.15mg/ml of proteinase K to digest 0.3mg/ml R-BSX and its mutants equilibrated in 20mM Tris-Cl,(pH 8.5) and urea (0–8M). Figure 2A–G shows the SDS-PAGE gel profile and ffold of R-BSX and its mutant after 1min pulse proteolysis. (H) _F4 mutant showed substantial proteolysis a...

GETAREA output for N- and C-terminus residues of BSX mutants. Mutated residues are shown in bold letter. Significant change in surface accessibility of any residue is shown in red color. (0.06 MB DOC)

DSC profile of R-BSX, _F4 and _W6. Figure 3A–C shows the DSC thermogram of R-BSX, _F4 and _W6. We used 0.1mg/ml of protein sample in 10mM Phosphate buffer, pH 7.0 with a heating rate of 333K/hr. in figure 3C, we can clearly see the aggregation during thermal unfolding of _W6 mutant which is indicated by the exothermic flow at the end of the denatur...

Stabilization strategies adopted by proteins under extreme conditions are very complex and involve various kinds of interactions. Recent studies have shown that a large proportion of proteins have their N- and C-terminal elements in close contact and suggested they play a role in protein folding and stability. However, the biological significance o...

We show here that oral immunization with purified outer membrane vesicles (OMVs) of Vibrio cholerae induces a prolonged high rise in the protective antibody titre. Rabbit immune sera were vibriocidal against the homologous and against several heterologous V. cholerae strains in vitro. In addition, OMV immunization conferred significant protective i...

A live oral cholera vaccine developed from a non-toxigenic Vibrio cholerae O1 El Tor strain VA1.3 was tested in a double-blind randomized placebo controlled study for safety and immunogenicity in 304 men aged between 16 and 50 years from Kolkata, India. A dose of 5 x 10(9)CFU (n=186) or a placebo (n=116) containing the diluent buffer was administer...

The role of mobile genetic elements in imparting multiple drug resistance to a clinical isolate of Vibrio fluvialis (BD146) was investigated. This isolate showed complete or intermediate resistance to all of the 14 antibiotics tested. Polymerase chain reaction (PCR) revealed the presence of a class 1 integron and the absence of the SXT element in t...

[This corrects the article on p. e3063 in vol. 3, PMID: 18725971.].

In earlier study from our group, cholera toxin B subunit had been expressed in tomato for developing a plant-based vaccine against cholera. In the present investigation, gene for accessory colonization factor (acf) subunit A, earlier reported to be essential for efficient colonization in the intestine, has been expressed in Escherichia coli as well...

For protection against cholera, it is important to develop efficient vaccine capable of inducing anti-toxin as well as anti-colonizing immunity against Vibrio cholerae infections. Earlier, expression of cholera toxin B subunit (CTB) in tomato was reported by us. In the present investigation, toxin co-regulated pilus subunit A (TCPA), earlier report...

Understanding the mechanisms that govern protein stability under poly-extreme conditions continues to be a major challenge. Xylanase (BSX) from Bacillus sp. NG-27, which has a TIM-barrel structure, shows optimum activity at high temperature and alkaline pH, and is resistant to denaturation by SDS and degradation by proteinase K. A comparative circu...

. a. Expression of recombinant TCPA in E. coli. The pQE30TCPA vector was generated and used for TCPA expression in E. coli. The expression was induced using 1 mM IPTG (isopropyl-b-D-thiogalactoside) b. Purified TCPA protein. The induced protein was purified by electro-elution. Further, electoeluted protein was purified using Qiagen’s Ni-NTA resin....

Vibrio cholerae strains have been reported to secret outer membrane vesicles (OMVs). In our study we purified and characterized OMV from N16961 V.cholerae, O1, Inaba strain. Oral immunization with purified outer membrane vesicle confer highly significant protective efficacy against homologous as well as heterologous challenge. This is the first tim...

Crystal structures are known for several glycosyl hydrolase family 10 (GH10) xylanases. However, none of them is from an alkalophilic organism that can grow in alkaline conditions. We have determined the crystal structures at 2.2 Angstroms of a GH10 extracellular endoxylanase (BSX) from an alkalophilic Bacillus sp. NG-27, for the native and the com...

Though the GroEL and DnaK heat shock proteins are well characterized in prokaryotes, only scanty and controversial information exist about their cellular localization. In the present study, the localization of the heat shock proteins DnaK and GroEL in normal and heat shocked cells of Vibrio cholerae, was investigated both by immunogold labeling of...

The molecular mechanisms of drug resistance in 19 strains of Vibrio fluvialis isolated from 1998 to 2002 in Kolkata, India, were investigated. Class 1 integrons were detected in eight strains, and four strains were found to carry SXT integrases. In the presence of carbonyl cyanide m-chlorophenylhydrazone or reserpine, all nalidixic acid- and ciprof...

Cholera toxin gene-negative Vibrio cholerae non-O1, non-O139 strain PL-21 is the etiologic agent of cholera-like syndrome. Hemagglutinin protease (HAP) is one of the major secretory proteins of PL-21. The mature 45-kDa and processed 35-kDa forms of HAP were purified in the presence and absence of EDTA from culture supernatants of PL-21. Enterotoxig...

Xylanases (EC 3.2.1.8) catalyze the hydrolysis of beta-1,4-glycosidic linkages within xylan, a major hemicellulose component in the biosphere. The extracellular endoxylanase (XylnA) from the alkalophilic Bacillus sp. strain NG-27 belongs to family 10 of the glycoside hydrolases. It is active at 343 K and pH 8.4. Moreover, it has attractive features...

We examined the distribution of class I integrons and SXT elements in Vibrio cholerae O1 El Tor strains, isolated in Calcutta, India, before and after the V. cholerae O139 outbreak in 1992. Class I integrons, with aadA1 gene cassette, were detected primarily in the pre-O139 strains; the SXT element was found mainly in the post-O139 strains.

Overproduction of cellulolytic enzymes through conventional nuclear transformation approaches posed a major challenge as they can potentially degrade the cell wall components and thereby affect transgenic plant growth and development. In this study, we have tested the possibility to over produce an alkali-thermostable xylanase gene from Bacillus sp...

Molecular mechanisms of multidrug resistance in Vibrio cholerae belonging to non-O1, non-O139 serogroups isolated during 1997 to 1998 in Calcutta, India, were investigated. Out of the 94 strains examined, 22 strains were found to have class I integrons. The gene cassettes identified were dfrA1, dfrA15, dfrA5, and dfrA12 for trimethoprim; aac(6′)-Ib...

This study identified 17 matching serogroups of Vibrio cholerae belonging to serogroups other than O1 and O139 isolated from human cases and from the environment during a concurrent clinical and environmental study conducted in Calcutta, a cholera endemic area. Isolates within these matching serogroups were compared by various phenotypic and genoty...

Xylanases form enzymes of considerable interest to a variety of biotechnological industries. Their industrial usage is especially attractive since they can replace some of the environmental pollutants, and are economically viable. Those with higher thermostability and optimal activity at alkaline pH are of particular importance to the paper and pul...

Alkalophilic Bacillus sp. strain NG-27 produces a 42-kDa endoxylanase active at 70°C and at a pH of 8.4. The gene for this endoxylanase was cloned and sequenced. The gene contained one open reading frame of 1,215 bases. An active site characteristic of the family 10 β-glycanases was recognized between amino acids 303 and 313, with the active glutam...

Vibrio cholerae WO7 (serogroup O1) isolated from patients with diarrhea produces an extracellular toxin despite the absence of ctx, zot, and ace genes from its genome. The toxin elongates Chinese hamster ovary cells, produces fluid accumulation in ligated rabbit ileal loops, and agglutinates freshly isolated rabbit erythrocytes. Maximal production...

The disease cholera is an important cause of mortality in many developing countries. Though it can be controlled through improved sanitation, this goal is not easily attainable in many countries. Development of an efficacious vaccine offers the best immediate solution. A new oral candidate vaccine has been constructed from a non-toxigenic strain of...

Though the GroEL and DnaK heat shock proteins are well characterized in prokaryotes, only scanty and controversial information exist about their cellular localization. In the present study, the localization of the heat shock proteins DnaK and GroEL in normal and heat shocked cells of Vibrio cholerae, was investigated both by immunogold labeling of...

Using molecular techniques, we investigated whether the clone of Vibrio cholerae O1 biotype El Tor which appeared in Calcutta, India, in 1994 has spread to other cholera endemic areas in the country. The ribotype of 31 of the 33 strains isolated from different parts of India during 1996 and 1997 was identical to the ribotype displayed by the new cl...

3), increased IgG intrathecal synthesis (IgG index 0·8; normal <0·7) and IgG oligoclonal bands, which confirmed acute encephalitis. PCR analysis for herpesvirus and antibodies, and antibodies to Epstein-Barr virus and to cytomegalovirus were negative in the serum and cerebrospinal fluid. Thoracic and abdominal computedtomography scans did not show...

We report the prevalence of the O139 serogroup in Calcutta, India, after its reemergence in August 1996 and the spread of the reemerged clone to other parts of the country by using previously established molecular markers. Phenotypically, the reemerged Vibrio cholerae O139 displayed a difference compared to those that appeared in late 1992 and 1993...

In the context of the reemergence of V. cholerae O1 in India and the recent evidence that O139 strains could have evolved from O1 E1 Tor strains, restriction fragment length polymorphism (RFLP) of the rRNA and the ctx genes and the antibiotic sensitivity profile of the two strains of V. cholerae, one an O1 and the other an O139, associated with mix...

There was an inexplicable upsurge in the incidence of non-O1, non-O139 Vibrio cholerae among hospitalized patients admitted to the Infectious Diseases Hospital, Calcutta, India, between February and March 1996. Of the 18 strains of V. cholerae isolated during this period, 15 belonged to the non-O1, non-O139 serogroups (4 belonged to O144, 3 belonge...

We present molecular evidence that a distinct genotype of Vibrio cholerae O1 which appeared in Calcutta, India, in September 1993 and which is characterized by a unique ribotype that is not found in the standardized ribotyping scheme of V. cholerae and that shows a specific pulsed-field gel electrophoresis profile may have spread to the west Africa...

After a lapse of 33 months, Vibrio cholerae O139, the new serogroup associated with cholera, has re-emerged in Calcutta, India and has become the dominant serogroup causing cholera from September 1996. In neighbouring Bangladesh, V. cholerae O1 biotype El Tor continues to be the dominant cause of cholera with the O139 serogroup accounting for only...

We studied the restriction fragment length polymorphism of the rRNA gene and CTX genetic element in Vibrio cholerae O139 Bengal, which resurged in Calcutta in September 1996 after a gap of 32 months. While the strains from this resurgence were indistinguishable from the earlier strains by ribotyping, the structure of the CTX genetic element present...

Sixty-one clinical strains of Vibrio cholerae Ol El Tor isolated in Calcutta before, during, and after the V. cholerae O139 Bengal outbreak were examined to see if the O1 strains of the post-O139 period were different from those in existence before. Comparison of the restriction fragment length polymorphism of the rRNA genes (ribotyping) and the CT...

Abstract An unusual filamentous bacteriophage, VSK, containing single-stranded, circular DNA as its genome was isolated from Vibrio cholerae 0139 strains P07 and B04. Unlike other single-stranded DNA phages, VSK can integrate its genome into the chromosome of the host and enter into a lysogenic state. The double-stranded replicative form (RF) of th...

First attempt at cholera vaccination was made by Jaime Ferran in 1884. Since then, a variety of strategies and methods have been evolved to create a safe, efficacious vaccine against cholera. For the first few years emphasis was on the development of parenteral vaccines. However, as a result of accumulation of a tremendous amount of knowledge, not...

Sixty-nine strains of Vibrio cholerae O1 isolated at different times were analysed to investigate if there were any differences among the O1 strains isolated before, during and after the advent of the O139 serogroup. Of the 69 O1 strains examined, 68 belonged to the Ogawa serotype while one belonged to the Inaba serotype. With the exception of one...

PCR analysis of formalin-fixed human autopsy tissues, rodent tissues, fleas and bacterial isolates from pneumonic patients from the 1991 plague epidemic confirmed the presence of the f1 and pla genes of Yersinia pestis in these samples, Several Y. pestis isolates from the epidemic areas were studied in respect of their plasmid profile, expression o...

General properties of the heat shock response in Vibrio cholerae were examined. Enhanced or de novo synthesis of 24 proteins was observed upon heat shock from 30 degrees C to 42 degrees C in cells labelled with [35S]methionine. A similar response could also be induced by a rise in temperature from 30 degrees C to 37 degrees C. Of these heat shock p...

A temperate bacteriophage isolated from Vibrio cholerae O139, the new epidemic strain of cholera, was found to have a polyhedral head 65 nm in diameter and a rigid contractile tail 120 nm in length. The phage chromosome was a double-stranded DNA of 35 kb, with unique cohesive ends and had a G + C content of 58.8%. A restriction map of the phage DNA...

Four outbreak strains of Vibrio cholerae O139 from endemic areas of India and Bangladesh were found to carry lysogenic phage(s). All of these phage(s) produced turbid plaques characteristic of lysogeny on V. cholerae MAK 757 (El Tor, Ogawa) cells as well as on their VcA-1 lysogens but were unable to infect V. cholerae 154 (classical) cells, the uni...

Wild-type Vibrio cholerae cells, when adapted by a stepwise treatment with sub-lethal concentrations of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), acquired resistance to killing and mutagenesis by subsequent challenges with higher concentrations of MNNG. This was also seen in the rec isogenic strain indicating that the observed phenomenon was not...

Four lines of evidence suggest that the recent outbreak strains of Vibrio cholerae 0139 could have emerged from serogroup 01 strains typified by isolates MOl and M0477 described in this paper, which are neither truly classical nor truly El Tor in their biotype attributes. Firstly, like all 0139 isolates, these 01 strains, isolated in Madras during...

A collection of Vibrio cholerae non-O1 isolated from the aquatic environs of Calcutta, a cholera-hyperendemic area, were examined for the production of cholera toxin (CT), Shiga-like toxins (Vero toxins), heat-stable enterotoxin, and hemolysins. Two (0.5%) V. cholerae non-O1 isolates produced CT. The DNA from both these isolates also hybridized wit...

Low concentrations of urea, which did not inhibit the synthesis of the catabolite nonrepressible enzyme alkaline phosphatase in Vibrio cholerae, or markedly affect its overall growth, specifically inhibited the expression of the tryptophanase operon in a temperature-dependent manner. However, in contrast to what is found in Escherichia coli, this u...

The survival of UV-irradiated cholera phage e5 was found to increase when the host cells, Vibrio cholerae MAK757, were exposed to a low dose of UV irradiation before phage infection (Weigle reactivation), indicating the existence of a UV-inducible DNA repair pathway (SOS repair) in V. cholerae MAK757. The induction signal generated by UV irradiatio...

A simple and rapid technique for quick identification of tryptophanase regulatory mutants and tryptophanase positive clones in a bacterial population is described. This method was used for the detection of tryptophanase regulatory mutants of Vibrio cholerae and tryptophanase positive recombinant clones of Escherichia coli.

Non-pathogenic, environmental strain ofVibrio cholerae, ELTOR Ogawa EW6 carries a copy of the cholera toxin gene in its chromosome. Restriction enzyme digestion followed by Southern blot analysis revealed that the structure of the cholera toxin gene in this organism is different from that found in the virulent strains. The xbaI site which has been...

Alkaline phosphatase activity in Vibrio cholerae strain 569B grown in low-phosphate medium was stimulated if glucose or glycerol was used as the carbon source. No such stimulation was observed, however, if tricarboxylic acid cycle intermediates like succinate or citrate were used. Experiments using specific enzyme inhibitors strongly indicated that...

The black beetle virus (BBV) is an isometric insect virus whose genome consists of two messenger-active RNA molecules encapsidated in a single virion. The nucleotide sequence of BBV RNA1 (3105 bases) has been determined, and this, together with the sequence of BBV RNA2 (1399 bases) provides the complete primary structure of the BBV genome. The RNA1...