Cobetia amphilecti sp. nov., Cobetia litoralis sp. nov. and Cobetia pacifica sp. nov., transfer of Halomonas halodurans NBRC 15607T to Cobetia marina and emended descriptions of the genus Cobetia and Cobetia marina
A group of five Gram-negative aerobic halotolerant non-pigmented bacteria isolated from shallow sediment samples and invertebrate specimen collected from the Gulf of Alaska and from the Sea of Japan was subjected to the taxonomic study. On the basis of 16S rRNA sequence analysis the novel isolates were affiliated to the genus Cobetia sharing the highest sequence similarities of 99.3-99.9% with the type strain of Cobetia marina DSM 4741T. The DNA-DNA hybridization experiments between novel strains themselves and towards Cobetia marina DSM 4741T and Cobetia crustatorum JCM 15644T revealed that five strains represent three separate genospecies, which could be differentiated in their morphological, physiological and biochemical characteristics. Strain Halomonas halodurans NBRC 15607T was included to the study as it has been recently reported to exhibit a high 16S rRNA gene sequence similarity to Cobetia marina DSM 4741T and it showed a high DNA relatedness value of 96% to C. marina DSM 4741T, indicating that they belong to the same species. On the basis of phylogenetic analysis, DNA-DNA hybridization and phenotypic characterization, three novel species, for which the names Cobetia amphilecti sp. nov. with the type strain KMM 1561T (=NRIC 0815T =CCUG 49560T), Cobetia litoralis sp. nov. with the type strain KMM 3880T (=NRIC 0814T =CCUG 49563T) and Cobetia pacifica sp. nov. with the type strain KMM 3879T (=NRIC 0813T =CCUG 49562T), are proposed.
[Show abstract][Hide abstract] ABSTRACT: Biosurfactants are produced by hydrocarbon-degrading marine bacteria in response to the presence of water-insoluble hydrocarbons. This is believed to facilitate the uptake of hydrocarbons by bacteria. However, these diffusible amphiphilic surface-active molecules are involved in several other biological functions such as microbial competition and intra- or inter-species communication. We report the isolation and characterization of a marine bacterial strain identified as Cobetia sp. MM1IDA2H-1, which can grow using the sulfur-containing heterocyclic aromatic hydrocarbon dibenzothiophene (DBT). As with DBT, when the isolated strain is grown in the presence of a microbial competitor, it produces a biosurfactant. Because the obtained biosurfactant was formed by hydroxy fatty acids and extracellular lipidic structures were observed during bacterial growth, we investigated whether the biosurfactant at its critical micelle concentration can interfere with bacterial communication systems such as quorum sensing. We focused on Aeromonas salmonicida subsp. salmonicida, a fish pathogen whose virulence relies on quorum sensing signals. Using biosensors for quorum sensing based on Chromobacterium violaceum and Vibrio anguillarum, we showed that when the purified biosurfactant was mixed with N-acyl homoserine lactones produced by A. salmonicida, quorum sensing was inhibited, although bacterial growth was not affected. In addition, the transcriptional activities of A. salmonicida virulence genes that are controlled by quorum sensing were repressed by both the purified biosurfactant and the growth in the presence of Cobetia sp. MM1IDA2H-1. We propose that the biosurfactant, or the lipid structures interact with the N-acyl homoserine lactones, inhibiting their function. This could be used as a strategy to interfere with the quorum sensing systems of bacterial fish pathogens, which represents an attractive alternative to classical antimicrobial therapies in fish aquaculture.
[Show abstract][Hide abstract] ABSTRACT: Halomonas has been organized as a genus since 1980, and comprises halophilic and/or halotolerant Gram-negative aerobic bacteria, typically found in saline environments. The genus is enlarging: at present, 76 species are taxonomically recognized, with more to be added. Increasing industrial uses have been found, largely in bioremediation and the production of desirable compounds. Originally seen as environmental contaminants, pathogenicity was initially not recognized; however, disease in algae, animals and humans has now been described. As the biotechnological use of these species increases, and the ability to isolate and recognize them improves, one might expect further pathogenic encounters with humans to be described.
[Show abstract][Hide abstract] ABSTRACT: The O-specific polysaccharide was isolated from the lipopolysaccharide of Cobetia pacifica KMM 3879(T) and studied by chemical methods along with (1)H and (13)C NMR spectroscopy, including 1D TOCSY and 2D (1)H, (1)H-COSY, ROESY, (1)H, (13)C-HSQC, HMBC, H2BC and HMQC-TOCSY experiments. The following new structure of the sulfated O-polysaccharide from the C. pacifica KMM 3879(T) containing rhamnose (Rha), glucose (Glc), and galactose (Gal) was established: where R is -SO3H.
Carbohydrate research 01/2014; 387C(1):4-9. DOI:10.1016/j.carres.2014.01.015 · 1.93 Impact Factor
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