RESUMO
Biodiversity of sulfate-reducing bacterial communities in the water column of the Gdansk Deep, Baltic Sea, where H2S had been detected in near-bottom layers, was analyzed by PCR with primers for the 16S rRNA genes of six major phylogenetic subgroups of sulfate-reducing bacteria (SRB). Using denaturing gradient gel electrophoresis followed by sequencing, the nucleotide sequences of reamplified dsrB gene fragments from investigated water samples were determined. For the first time the presence of nucleotide sequences of the dsrB gene was detected by PCR in the water samples from all hydrochemical layers, including subsurface oxic waters. The presence of the 16S rRNA genes of representatives of Desulfotomaculum, Desulfococcus-Desulfonema-Desulfosarcina, and Desulfovibrio-Desulfomicrobium SRB subgroups was also revealed throughout the water column of the Gdansk Deep. Analysis of translated amino acid sequences encoded by the dsrB gene demonstrated the highest homology with the relevant sequences of uncultured SRB from various marine habitats.
Assuntos
Deltaproteobacteria/classificação , Desulfotomaculum/classificação , Desulfovibrio/classificação , Genes Bacterianos , Bactérias Redutoras de Enxofre/classificação , Microbiologia da Água , Oceano Atlântico , Contagem de Colônia Microbiana , Deltaproteobacteria/genética , Deltaproteobacteria/metabolismo , Desulfotomaculum/genética , Desulfotomaculum/metabolismo , Desulfovibrio/genética , Desulfovibrio/metabolismo , Genes de RNAr , Sulfeto de Hidrogênio/metabolismo , Consórcios Microbianos/genética , Oxirredução , Filogenia , Reação em Cadeia da Polimerase , RNA Ribossômico 16S/genética , Bactérias Redutoras de Enxofre/genética , Bactérias Redutoras de Enxofre/metabolismoRESUMO
Like Lactobacillus leichmanii, Rhizobium meliloti, and Euglena gracilis, P. freudenreichii implicates cobalamin in DNA anabolism via adenosylcobalamin-dependent ribonucleotide reductase. However, in the absence of corrinoids, P. freudenreichii is able to synthesize DNA with the involvement of an alternative ribonucleotide reductase, which is independent of adenosylcobalamin. This enzyme is localized in both the cytoplasm (80% of activity) and the cytoplasmic membrane (20% of activity), being loosely bound to the latter. Experiments with crude ribonucleotide reductase isolated from extracts of corrinoid-deficient cells showed that manganese specifically stimulates this enzyme and that it is composed of two protein subunits, a feature that is typical of all metal-containing reductases activated by molecular oxygen. Low concentrations of manganese ions enhanced DNA synthesis in corrinoid-deficient manganese-limited cells. This effect was prevented by the addition of 80 mM hydroxyurea, a specific inhibitor of metal-containing aerobic ribonucleotide reductases. It was concluded that, in adenosylcobalamin-deficient P. freudenreichii cells, DNA synthesis is provided with deoxyribosyl precursors through the functioning of manganese-dependent aerobic ribonucleotide reductase composed of two subunits.
