Ecological Significance of Luminescence in Vibrio cholerae: Occurrence, Structure, Expression, and Function

Several Vibrio species are bioluminescent, including Vibrio cholerae. Analysis of 224 non-pathogenic V. cholerae isolates collected from the Chesapeake Bay, MD, revealed that 52% were luminescent, and 58% of the isolates harbor the luxA gene. A significant association of luxA to the gene stn (r = 0.40) was observed and luminescent strains were found to have a significant association with sample fraction and time of sampling, especially from the observed interaction of these two traits. In contrast, 334 non-pathogenic V. cholerae strains isolated from two rural provinces in Bangladesh, yielded 21 luminescent (6.3%) and 35 luxA+ (10.5%) isolates. None (0%) of 48 laboratory reference pathogenic strains from various geographic locations or 222 environmental and clinical isolated strains of V. cholerae O1 or O139 from Bangladesh were luminescent or harbored the lux operon. To improve success of isolation of V. cholerae from environmental samples, two colony blot hybridization methods were developed. Specificity of two probes was confirmed, using laboratory reference strains, in addition to environmental and clinical isolates, and sensitivity of the probes was confirmed using water samples into which V. cholerae had been inoculated. The lux operon of V. cholerae was sequenced and its chromosomal location determined. The operon organization is most similar to that of Shewanella hanedai and the non-luxF Photobacterium leiognathi. Sequence analysis revealed that the V. cholerae lux operon is most similar in its genomic sequence to V. harveyi and Photorhadbus luminescens and it most likely originated from a common Vibrionaceae ancestor. Using a new bioassay method that measures expression level, several classes of defective luminescent V. cholerae were identified and characterized, including one class previously termed dark, or K variants, in V. harveyi. Multiple causes of the defects were identified, indicating several levels of luminescence control in V. cholerae, in addition to autoinduction and lux repression. Using luxA mutants, luminescence was implicated in conveying competitive advantage in growth under microaerophilic conditions, DNA repair by photoreactivation, and neutralization of reactive oxidative species. These results demonstrate that bioluminescence is a frequently occurring trait in non-pathogenic V. cholerae, the expression of which gives a selective advantage in specific habitats

Occurrence and Diversity of Clinically Important Vibrio Species in the Aquatic Environment of Georgia

Among the more than 70 different Vibrio species inhabiting marine, estuarine, and freshwater ecosystems, 12 are recognized as human pathogens. The warm subtropical climate of the Black Sea coastal area and inland regions of Georgia likely provides a favorable environment for various Vibrio species. From 2006 to 2009, the abundance, ecology, and diversity of clinically important Vibrio species were studied in different locations in Georgia and across seasons. Over a 33-month period, 1,595 presumptive Vibrio isolates were collected from the Black Sea (n=657) and freshwater lakes around Tbilisi (n=938). Screening of a subset of 440 concentrated and enriched water samples by PCR-electrospray ionization/mass spectrometry (PCR-ESI/MS) detected the presence of DNA from eight clinically important Vibrio species: V. cholerae, V. parahaemolyticus, V. vulnificus, V. mimicus, V. alginolyticus, V. harveyi, V. metschnikovii, and V. cincinnatiensis. Almost ninety percent of PCR/ESI-MS samples positive for Vibrio species were collected from June through November. Three important human pathogenic Vibrio species (V. cholerae, V. parahaemolyticus, and V. vulnificus) were detected in 62.8%, 37.8%, and 21.4% of samples testing positive for vibrios, respectively. The results of these activities suggest that natural reservoirs for human-pathogenic Vibrios exist in Georgian aquatic environments. Water temperature at all sampling sites was positively correlated with the abundance of clinically important Vibrio spp. (except V. metschnikovii) and salinity was correlated with species composition at particular Black Sea sites as well as inland reservoirs

Characterizing a scientific elite: the social characteristics of the most highly cited scientists in environmental science and ecology

In science, a relatively small pool of researchers garners a disproportionally large number of citations. Still, very little is known about the social characteristics of highly cited scientists. This is unfortunate as these researchers wield a disproportional impact on their fields, and the study of highly cited scientists can enhance our understanding of the conditions which foster highly cited work, the systematic social inequalities which exist in science, and scientific careers more generally. This study provides information on this understudied subject by examining the social characteristics and opinions of the 0.1% most cited environmental scientists and ecologists. Overall, the social characteristics of these researchers tend to reflect broader patterns of inequality in the global scientific community. However, while the social characteristics of these researchers mirror those of other scientific elites in important ways, they differ in others, revealing findings which are both novel and surprising, perhaps indicating multiple pathways to becoming highly cited

Molecular Diversity and Predictability of Vibrio parahaemolyticus along the Georgian coastal zone of the Black Sea

Vibrio parahaemolyticus is a leading cause of seafood-related gastroenteritis and is also an autochthonous member of marine and estuarine environments worldwide. One hundred seventy strains of V. parahaemolyticus were isolated from water and plankton samples collected along the Georgian coast of the Black Sea during 28 months of sample collection. All isolated strains were tested for presence of tlh, trh, and tdh. A subset of strains were serotyped and tested for additional factors and markers of pandemicity. Twenty-six serotypes, five of which are clinically relevant, were identified. Although all 170 isolates were negative for tdh, trh, and the Kanagawa Phenomenon, 7 possessed the GS-PCR sequence and 27 the 850 bp sequence of V. parahaemolyticus pandemic strains. The V. parahaemolyticus population in the Black Sea was estimated to be genomically heterogeneous by rep-PCR and the serodiversity observed did not correlate with rep-PCR genomic diversity. Statistical modeling was used to predict presence of V. parahaemolyticus as a function of water temperature, with strongest concordance observed for Green Cape site samples (Percent of total variance = 70, P < 0.001). Results demonstrate a diverse population of V. parahaemolyticus in the Black Sea, some of which carry pandemic markers, with increased water temperature correlated to an increase in abundance of V. parahaemolyticus

Epidemiological Cutoff Values for Standard Broth Microdilution and Disk Diffusion Susceptibility Testing of Isolated from Fish

and other closely related species cause motile aeromonad septicemia, a common fish disease. The disease affects many aquaculture sectors potentially requiring antimicrobial treatments. Therefore, researchers and laboratory diagnosticians need criteria called epidemiological cutoff values (ECVs) to determine whether a bacterial isolate has developed decreased susceptibility to an antimicrobial. To generate ECVs for this bacterium, we assembled a diverse collection of 245 isolates previously identified as from fish. Using sequencing, we confirmed that 97 of the 245 isolates were . We allocated the isolates among three laboratories and tested their susceptibility against eight antimicrobials using standard Clinical and Laboratory Standards Institute (CLSI) disk diffusion and broth microdilution methods. The resulting frequency distributions were statistically analyzed to determine wild-type cutoff estimates, which, along with scatterplots, were used to estimate potential ECVs. In collaboration with the CLSI, aquaculture working group, we proposed ECVs for six of the eight antimicrobials tested. Subsequently, the CLSI Subcommittee on Veterinary Antimicrobial Susceptibility Testing reviewed our data and approved the ECVs to be added to the 2020 edition of the VET04 performance standards for antimicrobial susceptibility testing of aquatic bacteria