Isolamento de Bacillus sp. e gêneros correlatos de ecossistemas antárticos e potencial de prospecção para descoberta de antibióticos.

Resumo: O Continente Antartico possui condicoes extremas que favorecem a adaptacao a temperaturas muito baixas, e as bacterias sao os organismos mais adaptados. Bacterias do genero Bacillus sp. sao conhecidas por desenvolverem estruturas de resistencia (endosporos) e produzirem uma grande diversidade de antibioticos. Visando isolar especies de Bacillus e avaliar o potencial para producao de substâncias antimicrobianas, amostras de varios ecossistemas antarticos foram utilizados. Um total de 64 linhagens bacterianas foram isoladas, das quais 43,75% corresponderam ao genero Bacillus, 35,94% Brevibacillus, 14,06% Paenibacillus, 4,69% Sporosarcina. Dentre estas linhagens, 10,94% apresentaram potencial para producao de antibioticos contra Bacillus cereus, com a concentracao inibitoria minima (CIM) entre 62,5 a 250 microg/ml e Staphylococcus aureus, com CIM entre 150 a 500 microg/ml. Os metabolitos obtidos em BD foram mais ativos quando comparados aos obtidos em CN e a maior atividade antimicrobiana foi apresentada por biomoleculas de Bacillus amyloliquefaciens. Os resultados sugerem que o estresse ambiental que tais bacterias estao submetidas pode induzir o desenvolvimento de mecanismos de resistencia e adaptacao como a producao de esporos e de antibioticos, considerando-as fontes promissoras de metabolitos de interesse biotecnologicos. Abstract: The Antarctic continent with extreme conditions, present conditions for adaptations to very low temperature, and the bacteria are the organisms more adapted. Bacteria belonging to Bacillus sp. are known to develop resistance structures (endospores) as well as produce a wide variety of antibiotics. In order to isolate Bacillus sp. and assess their potential for antimicrobial substances production, samples from several Antarctic ecosystems were used. A total of 64 bacterial strains were isolated, of which 43.75% corresponded to the genus Bacillus, 35,94% Brevibacillus, 14,06% Paenibacillus and 4,69% Sporosarcina. Among these strains, 10.94% showed potential for the production of antibiotics against Bacillus cereus, with minimum inhibitory concentration (MIC) between 62,5 to 250 ?g/ml and Staphylococcus aureus, with MIC between 150 to 500 ?g/ml. The metabolites obtained from BD were more active when compared to those obtained in BD and the highest antimicrobial activity was presented by biomolecules from Bacillus amyloliquefaciens. The results suggest that the environmental stress that these bacteria are subjected to can induce the development of resistance mechanisms and adaptation as the production of spores and antibiotics, considering them as promising sources of biotechnological interest metabolites.