Isolation and characterization of Vibrio owensii from Palk Bay and its infection study against post larvae of Litopenaeus vannamei.

Vibrio is heterotrophic ubiquitous marine bacteria that plays dual role as putative halobiont and potential pathogen. Environment and diseases are inextricable hence the role of vibrio as a potential pathogen in the natural environment must be comprehended. Hence the present study aims at investigating the pathogenicity of Vibrio owensii on the post larvae of Litopenaeus vannamei. V. owensii isolated from the marine natural habitat of the Palk Bay province in India was highly resistant to ampicillin, methicillin, tetracycline and vancomycin. The strain also lacked pathogenicity against the post larvae of L. vannamei due to the absence of major virulence factors viz. Chitinase, phospholipase and hemolytic activity. Presumably this is the first report on the occurrence of V. owensii in the Indian waters therefore there arises a need to carry out more serious research on the pathogenicity of this species on other commercial crustaceans reared in the Indian aquaculture settings in order to apprehend its role as potential pathogen or the contrary.

Photobacterium piscicola sp. nov., isolated from marine fish and spoiled packed cod.

Five isolates from marine fish (W3(T), WM, W1S, S2 and S3) and three isolates misclassified as Photobacterium phosphoreum, originating from spoiled modified atmosphere packed stored cod (NCIMB 13482 and NCIMB 13483) and the intestine of skate (NCIMB 192), were subjected to a polyphasic taxonomic study. Phylogenetic analysis of 16S rRNA gene sequences showed that the isolates were members of the genus Photobacterium. Sequence analysis using the gapA, gyrB, pyrH, recA and rpoA loci showed that these isolates formed a distinct branch in the genus Photobacterium, and were most closely related to Photobacterium aquimaris, Photobacterium kishitanii, Photobacterium phosphoreum and Photobacterium iliopiscarium. The luxA gene was present in isolates W3(T), WM, W1S, S2 and S3 but not in NCIMB 13482, NCIMB 13483 and NCIMB 192. AFLP and (GTG)5-PCR fingerprinting indicated that the eight isolates represented at least five distinct genotypes. DNA-DNA hybridizations revealed 89% relatedness between isolate W3(T) and NCIMB 192, and values below 70% with the type strains of the phylogenetically closest species, P. iliopiscarium LMG 19543(T), P. kishitanii LMG 23890(T), P. aquimaris LMG 26951(T) and P. phosphoreum LMG4233(T). The strains of this new taxon could also be distinguished from the latter species by phenotypic characteristics. Therefore, we propose to classify this new taxon as Photobacterium piscicola sp. nov., with W3(T) (=NCCB 100098(T)=LMG 27681(T)) as the type strain.

Control of foodborne pathogens on fresh-cut fruit by a novel strain of Pseudomonas graminis.

The consumption of fresh-cut fruit has substantially risen over the last few years, leading to an increase in the number of outbreaks associated with fruit. Moreover, consumers are currently demanding wholesome, fresh-like, safe foods without added chemicals. As a response, the aim of this study was to determine if the naturally occurring microorganisms on fruit are "competitive with" or "antagonistic to" potentially encountered pathogens. Of the 97 and 107 isolates tested by co-inoculation with Escherichia coli O157:H7, Salmonella and Listeria innocua on fresh-cut apple and peach, respectively, and stored at 20 °C, seven showed a strong antagonistic capacity (more than 1-log unit reduction). One of the isolates, CPA-7, achieved the best reduction values (from 2.8 to 5.9-log units) and was the only isolate able to inhibit E. coli O157:H7 at refrigeration temperatures on both fruits. Therefore, CPA-7 was selected for further assays. Dose-response assays showed that CPA-7 should be present in at least the same amount as the pathogen to adequately reduce the numbers of the pathogen. From the results obtained in in vitro assays, competition seemed to be CPA-7's mode of action against E. coli O157:H7. The CPA-7 strain was identified as Pseudomonas graminis. Thus, the results support the potential use of CPA-7 as a bioprotective agent against foodborne pathogens in minimally processed fruit.

Historical microbiology: revival and phylogenetic analysis of the luminous bacterial cultures of M. W. Beijerinck.

Luminous bacteria isolated by Martinus W. Beijerinck were sealed in glass ampoules in 1924 and 1925 and stored under the names Photobacterium phosphoreum and 'Photobacterium splendidum'. To determine if the stored cultures were viable and to assess their evolutionary relationship with currently recognized bacteria, portions of the ampoule contents were inoculated into culture medium. Growth and luminescence were evident after 13 days of incubation, indicating the presence of viable cells after more than 80 years of storage. The Beijerinck strains are apparently the oldest bacterial cultures to be revived from storage. Multi-locus sequence analysis, based on the 16S rRNA, gapA, gyrB, pyrH, recA, luxA, and luxB genes, revealed that the Beijerinck strains are distant from the type strains of P. phosphoreum, ATCC 11040(T), and Vibrio splendidus, ATCC 33125(T), and instead form an evolutionarily distinct clade of Vibrio. Newly isolated strains from coastal seawater in Norway, France, Uruguay, Mexico, and Japan grouped with the Beijerinck strains, indicating a global distribution for this new clade, designated as the beijerinckii clade. Strains of the beijerinckii clade exhibited little sequence variation for the seven genes and approximately 6300 nucleotides examined despite the geographic distances and the more than 80 years separating their isolation. Gram-negative bacteria therefore can survive for many decades in liquid storage, and in nature, they do not necessarily diverge rapidly over time.

Beijerinck and the bioluminescent bacteria: microbiological experiments in the late 19th and early 20th centuries.

Microbiological research in the days before specialized equipment, or even electricity, required a great deal of ingenuity. The revival of 90-year-old bioluminescent bacteria from Beijerinck's laboratory in Delft prompted a review of his work with these microorganisms and revealed their use in simple techniques for the investigation of, among other things, sugar metabolism in yeasts, oxygen generation and uptake and even the survival of microorganisms in liquid hydrogen. He used variant strains of bioluminescent bacteria in an attempt to study heredity and variation in biological systems and described one of the earliest examples of enzyme induction.

Collimonas fungivorans gen. nov., sp. nov., a chitinolytic soil bacterium with the ability to grow on living fungal hyphae.

A polyphasic approach was used to describe the phylogenetic position of 22 chitinolytic bacterial isolates that were able to grow at the expense of intact, living hyphae of several soil fungi. These isolates, which were found in slightly acidic dune soils in the Netherlands, were strictly aerobic, Gram-negative rods. Cells grown in liquid cultures were flagellated and possessed pili. A wide range of sugars, alcohols, organic acids and amino acids could be metabolized, whereas several di- and trisaccharides could not be used as substrates. The major cellular fatty acids were C(16 : 0), C(16 : 1)omega7c and C(18 : 1)omega7c. DNA G+C contents were 57-62 mol%. Analysis of nearly full-length 16S rDNA sequences showed that the isolates were related closely to each other (>98.6 % sequence similarity) and could be assigned to the beta-Proteobacteria, family 'Oxalobacteraceae', order 'Burkholderiales'. The most closely related species belonged to the genera Herbaspirillum and Janthinobacterium, exhibiting 95.9-96.7 % (Herbaspirillum species) and 94.3-95.6 % (Janthinobacterium species) 16S rDNA sequence similarity to the isolates. Several physiological and biochemical properties indicated that the isolates could be distinguished clearly from both of these genera. Therefore, it is proposed that the isolates described in this study are representatives of a novel genus, Collimonas gen. nov. Genomic fingerprinting (BOX-PCR), detailed analysis of 16S rDNA patterns and physiological characterization (Biolog) of the isolates revealed the existence of four subclusters. The name Collimonas fungivorans gen. nov., sp. nov. has been given to one subcluster (four isolates) that appears to be in the centre of the novel genus; isolates in the other subclusters have been tentatively named Collimonas sp. The type strain of Collimonas fungivorans gen. nov., sp. nov. is Ter6(T) (=NCCB 100033(T)=LMG 21973(T)).