Eficácia da hipoxantina-3-N-óxido como método alternativo na proteção da ictiofauna em usinas hidrelétricas: Efficacy of hypoxanthine-3-N-oxide as an alternative method to protect ichthyofauna in hydroelectric power plants

As substâncias de alarme, liberadas após danos às células epidérmicas de peixes, é um dos sinais mais eficientes no grupo Osteriophysan, isto é, 72% das espécies de água doce. A hipoxantina-3-N-óxido é indicada como um dos possíveis componentes ativos dessas substâncias. Ensaios foram feitos com as espécies Matrinxã e Tambaqui através de aquários com capacidade de 100 L, instrumentalizados com sistemas de introdução de amostra e aquisição de imagens de forma remota. Os resultados indicaram na concentração de 6,0 µg L-1 alterações comportamentais incomuns como letargia, forrageio para o fundo e ataques, que apoiam a premissa de que a hipoxantina-3-N-óxido é eficaz na indução de sinais de alarme. A hipoxantina pode ser futuramente um bom método de manejo para proteção da ictiofauna, sobretudo no setor hidrelétrico, por ter eficácia comprovada, ser uma substância sintética, comercial e não tóxica à biota e ao ambiente aquático

Potential of Bacterial Isolates from a Stream in Manaus-Amazon to Bioremediate Chromium-Contaminated Environments

Igarapé do Quarenta (IgQ), a stream located in the Manaus-AM, BR, has directly experienced the impacts of urban expansion over the last five decades, which contributed for its contamination. As an affluent of Rio Negro, IgQ also affects the water quality of this important river that bathes Manaus. However, the stress caused by the prolonged exposition to chemical agents may have selected microorganisms that exhibit great bioremediation potential. In the present study, bacteria isolated from four distinct sites of the IgQ were identified, and their potential to degrade hexavalent chromium (Cr(VI)) was investigated using the s-diphenylcarbazide method. Among the investigated isolates, 14 exhibited resistance against Cr(VI) at a concentration of 300 mg/L and eight isolates reduced over 50% (53.5–97.4%) chromium ratios after 72 h of incubation. Those isolates were identified by gene sequencing and classified in 10 genera (Acidovorax sp., Acinetobacter sp., Alicycliphilus sp., Bacillus sp., Comamonas sp., Enterobacter sp., Micrococcus sp., Proteus sp., Serratia sp., and Vagococcus sp.). Under control conditions, the isolate of Vagococcus sp. genus, in only 24 h of incubation, reduced 96.8% of the rate of Cr(VI) added to the culture medium at the concentration of 10 mg/L. Obtained results indicate that the Vagococcus sp. exhibits a great potential to be used in the bioremediation of areas contaminated with chromium. The mechanisms of action of microorganisms should be investigated for more specific applications in the decontamination of effluents and direct use of its by-products to bioremediate polluted environments. © 2018, The Author(s)