Genetic and phenetic classification of bacteria

Vibrio VopQ induces PI3-kinase-independent autophagy and antagonizes phagocytosis

Vibrio parahaemolyticus is a Gram-negative bacterium responsible for gastroenteritis acquired from the consumption of contaminated shellfish. This bacterium harbours two type III secretion systems, one on each chromosome. The type III secretion system on chromosome I induces cell death by a temporally controlled sequence of events that is caspase-independent and first involves induction of autophagy, followed by cellular rounding, and finally cellular lysis. VopQ is a type III secreted effector that is necessary for the induction of autophagy as mutant strains lacking VopQ are attenuated in their ability to induce autophagy during infection. VopQ is sufficient to induce rapid autophagy as demonstrated by microinjection of recombinant VopQ into GFP-LC3 HeLa cells. Our results demonstrate that VopQ is both necessary and sufficient for induction of autophagy during V. parahaemolyticus-mediated cell death and this effect is independent of phosphatidylinositol-3-kinases but requires Atg5. Furthermore, induction of VopQ-mediated autophagy prevents recruitment of the necessary cellular machinery required for phagocytosis of V. parahaemolyticus during infection. These data provide important insights into the mechanism used by V. parahaemolyticus to cause disease.

Effects of global climate on infectious disease: the cholera model

Recently, the role of the environment and climate in disease dynamics has become a subject of increasing interest to microbiologists, clinicians, epidemiologists, and ecologists. Much of the interest has been stimulated by the growing problems of antibiotic resistance among pathogens, emergence and/or reemergence of infectious diseases worldwide, the potential of bioterrorism, and the debate concerning climate change. Cholera, caused by Vibrio cholerae, lends itself to analyses of the role of climate in infectious disease, coupled to population dynamics of pathogenic microorganisms, for several reasons. First, the disease has a historical context linking it to specific seasons and biogeographical zones. In addition, the population dynamics of V. cholerae in the environment are strongly controlled by environmental factors, such as water temperature, salinity, and the presence of copepods, which are, in turn, controlled by larger-scale climate variability. In this review, the association between plankton and V. cholerae that has been documented over the last 20 years is discussed in support of the hypothesis that cholera shares properties of a vector-borne disease. In addition, a model for environmental transmission of cholera to humans in the context of climate variability is presented. The cholera model provides a template for future research on climate-sensitive diseases, allowing definition of critical parameters and offering a means of developing more sophisticated methods for prediction of disease outbreaks.

Biosystematics and diversity amongst novel carboxydotrophic actinomycetes

Fifty-four carboxydotrophic actinomycetes isolated from soils and composts were compared through 119 unit characters with representative mesophilic and thermophilic streptomycetes. The data were examined using the Jaccard, pattern and simple matching coefficients and clustering achieved using the unweighted pair group method with arithmetic averages algorithm. Acceptable cophenetic correlation and test error values allowed confidence to be placed in the resultant numerical taxonomies. The carboxydotrophic actinomycetes, which were distinct from cluster-groups corresponding to the mesophilic and thermophilic streptomycetes, formed two major cluster-groups the members of which were examined for the presence of diagnostic chemical markers. All but two of the carboxydotrophic actinomycetes had a profile of chemical properties consistent with their assignment to the genus Streptomyces. Quantitative fatty acid data were examined using the SIMCA package and the two statistically significant groups obtained corresponded with the cluster-groups circumscribed in the numerical phenetic analysis. Members of the two groups were also distinguished on the basis of their phospholipid composition. The two strains that contained meso-as opposed to LL-diaminopimelic acid in their peptidoglycan also showed a distinct chemotaxonomic profile. It was concluded that the carboxydotrophic actinomycetes form a novel and taxonomically diverse group.

Numerical taxonomy of Vibrio cholerae and related species isolated from areas that are endemic and nonendemic for cholera

A total of 165 strains of vibrios isolated from clinical and environmental sources in the United States, India, and Bangladesh, 11 reference cultures, and 4 duplicated cultures were compared in a numerical taxonomic study using 83 unit characters. Similarity between strains was computed by using the simple matching coefficient and the Jaccard coefficient. Strains were clustered by unweighted average linkage and single linkage algorithms. All methods gave similar cluster compositions. The estimated probability of error in the study was obtained from a comparison of the results of duplicated strains and was within acceptable limits. A total of 174 of the 180 organisms studied were divided into eight major clusters. Two clusters were identified as Vibrio cholerae, one as Vibrio mimicus, one as Vibrio parahaemolyticus, three as Vibrio species, and one as Aeromonas hydrophila. The V. mimicus cluster could be further divided into two subclusters, and the major V. cholerae group could be split into seven minor subclusters. Phenotypic traits routinely used to identify clinical isolates of V. cholerae can be used to identify environmental V. cholerae isolates. No distinction was found between strains of V. cholerae isolated from regions endemic for cholera and strains from nonendemic regions.

Numerical taxonomy of Pseudomonas based on published records of substrate utilization

Data published by R. Y. Stanier, N. J. Palleroni, M. Doudoroff and their colleagues on Pseudomonas have been analysed by numerical taxonomy. Records on 401 strains were used, representing 155 characters, mostly utilization of substrates as carbon-energy sources. Twenty-nine phenons were recognized, which included 394 strains: the remaining 7 remained unclustered. The results were in very good accord with the conclusions of these authors. Almost all phenons were well separated with very little overlap. Many of them corresponded to distinct species, and others corresponded to recognized biotypes. Some small groups may represent unnamed new species. Analyses by Gower's Coefficient showed five major groupings: A) the fluorescent pseudomonads; B) biochemically active species (Pseudomonas cepacia, P. pseudomallei and allies); C) moderately active free-living species (P. acidovorans, P. alcaligenes and allies); D) P. solanacearum and allies; and #) P. mallei P. diminuta does not appear to be clearly distinct from P. vesicularis, nor does P alcaligenes appear clearly distinct from P. pseudoalcaligenes. There may, however, be some difference between P. multivorans and P. cepacia. Analyses using the Pattern Coefficient differed mainly in the relationships shown by a few of the metabolically active species. Of the two coefficients, the Pattern Coefficient gave results that were in somewhat better agreement with evidence from nucleic acids, but it showed an unexpectedly close relationship between P. solanacearum and P. cepacia.