Taxonomia de pracriontes isolados de cnidários de São Sebastião, SP, Brasil / Taxonomy of prokaryontes isolated from cnidarians of São Sebastião, SP, Brasil

AUTOR(ES)
FONTE

IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia

DATA DE PUBLICAÇÃO

30/04/2010

RESUMO

Microorganisms have a key role in the health of cnidarians establishing ecologic relationships, of parasitism to mutualism. The knowledge on the diversity of prokaryotes associated with corals in Brazil is very limited. This is the first study on the taxonomic characterization of heterotrophic bacteria, including putative N2-fixing and specially vibrios isolated from mucus of endemic coral Mussismilia hispida and the sympatric zoanthids Palythoa caribaeorum, Palythoa variabilis and Zoanthus solanderi. Cnidarian specimens were isolated in the beaches Grande, Portinho and Preta from São Sebastião region, SP, Brazil, in 2005 and 2006. A total of 488 isolates were obtained using different culture media, i.e. Marine Agar (MA), Nitrogen Fixation (NFb) and Thiosulphate-Citrate- Bile-Sucrose Agar (TCBS). The majority of the isolates fell within the class Gammaproteobacteria and more than half of them were vibrios based on 16S rRNA gene sequences. Based on pyrH gene sequences 80 % of the putative N2-fixing bacteria clustered with the Vibrio core species group (i.e. V. harveyi and V. alginolyticus). Nineteen representative isolates of V. harveyi, V. alginolyticus, V. campbellii and V. parahaemolyticus) were capable of growing six successive times in nitrogen-free medium and some of them showed strong nitrogenase activity by means of the acetylene reduction assay (ARA). About 150 vibrios isolated on TCBS were characterized by means of 16S rRNA, recA and pyrH gene sequences. The most abundant taxa were V. harveyi, V. rotiferianus, V. campbellii, V. alginolyticus, V. mediterranei (=V. shillonii), V. chagasii, V. tubiashii and a new Vibrio species. With the exception of V. chagasii which was found only in the mucus of M. hispida, the other species appeared in different hosts with no strong evidence for the presence of host-specific species. A high genomic diversity was observed using rep-PCR. Each vibrio isolate represented a different co-occuring population, suggesting huge intra-especific diversity. There was a complete agreement between the grouping based on rep-PCR and identification based on MLSA (Multilocus Sequence Analysis). Several isolates had less than 97 % similarity towards know species based on 16S rRNA gene sequence, indicating that they are possibly new species. In total, seven new species were described based on polyphasic taxonomy: Marinobacterium coralli sp. nov., Marinomonas brasilensis sp. nov. Photobacterium swingsii sp. nov., P. jeanii sp. nov., Vibrio communis sp. nov., V. variabilis sp. nov. and V. marinum sp. nov. The new species were characterized by polyphasic taxonomy. Based on phenotypic, chimiotaxonomic, genotypic and phylogenetic data obtained from description of new species, it was demonstrated a huge intra-specific phenotypic variability. This study determined the taxonomic identity of heterotrophic bacteria, especially Vibrio, isolates from cnidarians. V. communis sp. nov. is one of the most frequently found species in the corals. Nitrogen fixation is a common phenotypic trait among vibrios, suggesting that these bacteria may have a positive function in the holobiont.

ASSUNTO(S)

taxonomia procariotes cnidários taxonomy procaryotes cnidaria

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