RESUMO
The goal of this study was to use environmental sequencing of 16S rRNA and bop genes to compare the diversity of planktonic bacteria and archaea across ponds with increasing salinity in the Exportadora de Sal (ESSA) evaporative saltern in Guerrero Negro, Baja CA S., Mexico. We hypothesized that diverse communities of heterotrophic bacteria and archaea would be found in the ESSA ponds, but that bacterial diversity would decrease relative to archaea at the highest salinities. Archaeal 16S rRNA diversity was higher in Ponds 11 and 12 (370 and 380 g l(-1) total salts, respectively) compared to Pond 9 (180 g l(-1) total salts). Both Pond 11 and 12 communities had high representation (47 and 45% of clones, respectively) by Haloquadratum walsbyi-like (99% similarity) lineages. The archaeal community in Pond 9 was dominated (79%) by a single uncultured phylotype with 99% similarity to sequences recovered from the Sfax saltern in Tunisia. This pattern was mirrored in bop gene diversity with greater numbers of highly supported phylotypes including many Haloquadratum-like sequences from the two highest salinity ponds. In Pond 9, most bop sequences, were not closely related to sequences in databases. Bacterial 16S rRNA diversity was higher than archaeal in both Pond 9 and Pond 12 samples, but not Pond 11, where a non-Salinibacter lineage within the Bacteroidetes >98% similar to environmental clones recovered from Lake Tuz in Turkey and a saltern in Chula Vista, CA was most abundant (69% of community). This OTU was also the most abundant in Pond 12, but only represented 14% of clones in the more diverse pond. The most abundant OTU in Pond 9 (33% of community) was 99% similar to an uncultured gammaproteobacterial clone from the Salton Sea. Results suggest that the communities of saltern bacteria and archaea vary even in ponds with similar salinity and further investigation into the ecology of diverse, uncultured halophile communities is warranted.
RESUMO
Solar salterns are extreme hypersaline environments that are five to ten times saltier than seawater (150-300 g L(-1) salt concentration) and typically contain high numbers of halophiles adapted to tolerate such extreme hypersalinity. Thirty-five halophile cultures of both Bacteria and Archaea were isolated from the Exportadora de Sal saltworks in Guerrero Negro, Baja California, Mexico. 16S rRNA sequence analysis showed that these cultured isolates included members belonging to the Halorubrum, Haloarcula, Halomonas, Halovibrio, Salicola, and Salinibacter genera and what may represent a new archaeal genus. For the first time, metabolic substrate usage of halophile isolates was evaluated using the non-colorimetric BIOLOG Phenotype MicroArray plates. Unique carbon substrate usage profiles were observed, even for closely related Halorubrum species, with bacterial isolates using more substrates than archaeal cultures. Characterization of these isolates also included morphology and pigmentation analyses, as well as salinity tolerance over a range of 50-300 g L(-1) salt concentration. Salinity optima varied between 50 and 250 g L(-1) and doubling times varied between 1 and 12 h.
Assuntos
Archaea/metabolismo , Bactérias/metabolismo , RNA Ribossômico 16S/genética , Água do Mar/microbiologia , Biodiversidade , Colorimetria/métodos , Variação Genética , México , Filogenia , Pigmentação , Tolerância ao Sal , Sais/química , Especificidade por Substrato , Microbiologia da ÁguaRESUMO
The Guaymas Basin (Gulf of California) is a hydrothermal vent site where thermal alteration of deposited planktonic and terrestrial organic matter forms petroliferous material which supports diverse sulfate-reducing bacteria. We explored the phylogenetic and functional diversity of the sulfate-reducing bacteria by characterizing PCR-amplified dissimilatory sulfite reductase (dsrAB) and 16S rRNA genes from the upper 4 cm of the Guaymas sediment. The dsrAB sequences revealed that there was a major clade closely related to the acetate-oxidizing delta-proteobacterial genus Desulfobacter and a clade of novel, deeply branching dsr sequences related to environmental dsr sequences from marine sediments in Aarhus Bay and Kysing Fjord (Denmark). Other dsr clones were affiliated with gram-positive thermophilic sulfate reducers (genus Desulfotomaculum) and the delta-proteobacterial species Desulforhabdus amnigena and Thermodesulforhabdus norvegica. Phylogenetic analysis of 16S rRNAs from the same environmental samples resulted in identification of four clones affiliated with Desulfobacterium niacini, a member of the acetate-oxidizing, nutritionally versatile genus Desulfobacterium, and one clone related to Desulfobacula toluolica and Desulfotignum balticum. Other bacterial 16S rRNA bacterial phylotypes were represented by non-sulfate reducers and uncultured lineages with unknown physiology, like OP9, OP8, as well as a group with no clear affiliation. In summary, analyses of both 16S rRNA and dsrAB clone libraries resulted in identification of members of the Desulfobacteriales in the Guaymas sediments. In addition, the dsrAB sequencing approach revealed a novel group of sulfate-reducing prokaryotes that could not be identified by 16S rRNA sequencing.