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We isolated 41 and characterized 17 microsatellite loci for evaluating the genetic structure of the Amazonian fish Hypophthalmus marginatus, from the Tocantins and Araguaia River in the Eastern Amazonia. Of the 17 selected microsatellite sequences, 15 were dinucleotide repeats, 9 of which were perfect (5–31 repetitions) and 6 were composite motifs. Among these 17 microsatellites, only two were polymorphic. The average number of alleles (Na) observed in the five examined populations ranged from 3.5 to 4.5, while the average observed heterozygosity (Ho) ranged from 0.3 to 0.6. The allelic frequency was less homogeneous at the locus Hm 5 than that for the Hm 13. Genetic diversity was measured in three upstream and two downstream populations under the influence of the Tucurui Hydroelectric Dam. Our findings provide evidence for low levels of genetic diversity in H. marginatus of the Tocantis basin possibility related to the Dam construction. The Fst and Rst analysis fits well with migratory characteristics of H. marginatus, suggesting the existence of a gene flow mainly in the upstream or downstream directions. To test the hypothesis that the Dam was responsible for the detected reduction on this species genetic diversity, a large number of genetic markers are recommended, covering geographic distribution range of the fish species.

Mangroves form a transition zone among terrestrial, marine, and freshwater environments, and they host a striking diversity of macro- and microorganisms. In recent years, increasing anthropogenic impacts have caused widespread degradation of mangrove environments. To analyze the bacterial diversity of Salina Lake, an artificial body of water located in the mangroves of eastern Amazonia, total DNA was extracted from sediment and water samples that were collected from three sites (P1, P2, P3) located within the lake. The 16S rRNA gene was partially amplified, separated using the Denaturing High Performance Liquid Chromatography (DHPLC) method, and sequenced. The DHPLC profiles were quite distinct for the different aquatic and sedimentary bacterial communities. The most abundant groups (> 70%) at all sampled locations were Proteobacteria and unclassified bacteria, but other phyla were also identified, including Bacteroidetes, Cyanobacteria, Acidobacteria, Firmicutes, Actinobacteria, Chloroflexi, Siprochaetes and TM7 . A total of 24, 15, and 23 OTUs (Operational Taxonomic Units) were observed in the water samples from P1, P2, and P3, respectively, whereas the sediment samples returned 29, 34, and 52 OTUs. This is the first analysis performed on the bacterial diversity of Salina Lake, which was created by the construction of a highway within a protected mangrove area.

The Amazon region has several hydroelectric power reservoirs and, among these, is the Tucurui reservoir, which has the fourth highest power in the world. This reservoir flooded a huge area of native forest, whose organic matter has been decomposed in the water column since then. This microbial process is carried out by several prokaryotic species, which present a great metabolic diversity, including among them methanotrophic bacteria and methanogens. In this study we sought to evaluate the community structure, composition and diversity along a water column of the Tucurui reservoir located upstream of the dam by using denaturing high performance liquid chromatography (DHPLC) and 16S rDNA gene sequencing. Water samples were taken at intervals of 5 m from the surface down to a depth of 55 m along the water column. Our results show that the structures of communities of both Archaea and Bacteria remained constant down to a depth of 35 m indicating the existence of a stable environment until this depth. Changes in the abundance of some groups could be observed at the 40 m depth and the composition of the communities changed significantly at the depths of 45, 50 and 55 m. The deepest layer (55 m) presented the highest Archaeal diversity, while the highest Bacterial diversity was observed at the 0-40 m layers. Crenarchaeota were predominant in the upper layers, while Euryarchaeota , including methanogenic Archaea, were predominant in the 40 and 50 m layers, indicating the existence of an anoxic zone below 40 m. Actinobacteria, Bacteroidetes and Proteobacteria sequences were recovered from the superficial layers, as well as sequences not assigned to any phylum. Several sequences from the 55 m layer were assigned to Dechloromonas , known for the ability to degrade benzene and other aromatic compounds. We conclude that the structure and diversity of prokaryotic communities in the Tucurui power reservoir is stable until the 35 m depth, changing in deeper layers.

Chromobacterium violaceum ATCC 12472 presents an arsRCB-type operon, which is involved in arsenic resistance. The regulating protein of this resistance system (ArsR) does not have the small conserved site (ELCVDCL) to link to the metalloid, as observed in Escherichia coli , and is thus considered to be an atypical ArsR protein, like that observed in Acidithiobacillus ferrooxidans . In the present study, the gene expression profile of the ars operon under induction at different concentrations of arsenite — As(III) — was obtained via real-time PCR (TaqMan), by correlating the threshold cycle (Ct) values of induced and uninduced (control) samples. Through linear regression analysis (R2= 0.9926), the gene expression profile of the ars operon showed clearly that the 0.125 μmol/L concentration of As(III) was sufficient to provoke a 4-fold increase in the resistance system, and a further increase in concentration resulted in an increase of up to 53-fold in transcription rates. The relation between resistance and induction of the ars operon indicates that the increased resistance to As(III) is associated with the increase in the number of transcripts.

Chromobacterium violaceum is a Gram-negative bacterium found in a wide variety of tropical and subtropical ecosystems. The complete genome sequence of C. violaceum ATCC 12472 is now available, and it has considerable biotechnological potential for various applications, such as environmental detoxification, as well as medical and agricultural use. We examined the biotechnological potential of C. violaceum for environmental detoxification. Three operons, comprising the ars operon, involved in arsenic resistance, the cyn operon, involved in cyanate detoxification, and the hcn operon, encoding a cyanase, responsible for biogenic production of cyanide, as well as an open reading frame, encoding an acid dehalogenase, were analyzed in detail. Probable catalytic mechanisms for the enzymes were determined, based on amino acid sequence comparisons and on published structural information for these types of proteins.