Biogeografia e caracterização molecular e fisiológica de bactérias heterotróficas, com ênfase em Chromobacterium, dos biomas Mata Atlântica e Cerrado

Abstract

Biogeography studies the space and temporary distribution of the species of living beings and tries to understand the factors that control their abundance. This study aimed to investigate the diversity and biogeography of cultivable heterotrophic bacteria from two Brazilian conservation units: Serra do Cipó National Park (PNSC, Cerrado) and Rio Doce State Park (PERD, Atlantic Rainforest), using a polyphasic approach. Of 936 bacterial isolates studied, 111 isolates exhibited violet pigmentation. These were isolated from the waters of Córrego Indaiá (74) and from the soil of its environs (37), PNSC. The remaining isolates (825) were retrieved from nine points of the euphotic and horizontal gradients (100%, 10% and 1% of light penetration) of the Carioca Lake (PERD), in June and August of 2007. Phylogeny of 16S rRNA gene suggested that the 111 violet isolates were related with Chromobacterium piscinae. All C. piscinae isolates presented high resistance to ampicillin, and their physiological profiles, generated by BIOLOG GN2, showed high versatility in the substrata use. The clusters obtained by BOX-PCR fingerprinting and by antimicrobial susceptibility showed clear separation among the isolates from soil and from water, indicating a strong endemism of the populations. The physiological profile of the 18 microbial communities from the Carioca Lake, obtained by BIOLOG Ecoplates, revealed high metabolic diversity, although it was possible to distinguish two groupings, which were delimited by their temporal origin. Among the 825 isolates from the lake, 673 of them produced 360 OTUs (operational taxonomic units) by ARDRA (Amplified Ribosomal DNA Restriction Analysis), of which 313 were unique, indicating strong endemism. Further, OTUs-ARDRA was identified for the 16S rDNA sequencing and was affiliated to five phyla, ordered by its abundance: Proteobacteria, Firmicutes, Actinobacteria, Bacteroidetes and Deinococcus-Thermus, represented by 39 genera. Mantel testing pointed the relationship between the communities composition and few abiotic factors (turbidity, total N, and NO2), especially when the comparison was done among the communities in July and August. A population of 31 isolates of Chromobacterium, the most abundant genus, was characterized and identified by 16S rDNA as C. haemolyticum. In our knowledge, this is the first characterization of environmental isolates from this species. These isolates exhibited genetic heterogeneity revealed by the 16S rDNA and the analyses of ITS and BOX-PCR. It also stands out that, during the purification process, some peculiar colonies (76 from 1196) harbored two to five bacterial isolates, which were named .associated isolates.. Surprisingly, after the purification some of them lost their viability. Most of the colonies harboring multiple isolates presented two associated isolates. Interestingly, colonies harboring four or five associated isolates were obtained exclusively at 1% of the euphotic gradient. The taxonomic identity of the 121 associated isolates revealed the presence of the same five phyla already found, although in this study the Curtobacterium and Williamsia genera have been exclusive.