Detoxification of Atrazine by Endophytic Streptomyces sp. Isolated from Sugarcane and Detection of Nontoxic Metabolite.

Atrazine is still one of the most used agricultural pesticides worldwide and it has been recognized as a major contaminant of surface and ground water. The aims of this research were to isolate an endophytic microorganism from leaves of sugarcane, evaluate its ability to degrade atrazine, and investigate the formation of metabolites. By sequencing of the 16S rRNA gene, the endophytic isolate atz2 was identified as Streptomyces sp. The reduction in atrazine concentration by Streptomyces sp. atz2 was 98 % and UHPLC-MS/MS analyses showed the appearance of an unknown metabolite observed as m/z 311. Ecotoxicity tests with an aquatic organism, Daphnia similis, confirmed that this metabolite was nontoxic. This mechanism of detoxification of atrazine is different from the ones of other free-living microorganisms that inhabit the soil or rhizosphere. The results show new aspects of atrazine detoxification, highlighting a new role of endophytic bacteria in plants.

Catalase activity of different Candida species after exposition to specific antiserum

Antisera were developed in rabbits after challenge with intracellular antigens of Candida albicans, C. tropicalis and C. parapsilosis. Microorganism catalase has been correlated with virulence, resistance to drugs and immunogenicity. The intracellular catalase is consistently present in strains of Candida and in this paper, the enzyme activity was analysed by PAGE after exposition to antisera. The catalases of C. albicans, C. parapsilosis and C. tropicalis were immunogenic and differed in their binding to specific antibodies raised in rabbits. Tests of cross-reactivity between different Candida species showed that when antiserum from C. albicans immunized rabbit was incubated with intracellular extracts of these three Candida species, the catalases activities were abolished. However, the antisera from C. parapsilosis or C. tropicalis immunized rabbits did not affect the catalase activity of C. albicans; the enzyme of C. albicans was inactivated only by the antiserum to the catalase of own C. albicans. The antiserum to the catalase of C. tropicalis was species-specific and did not cross-react with catalases of C. albicans and C. parapsilosis. The activities of Aspergillus niger and bovine catalases were not affected by the antiserum from any Candida immunized rabbits. This report is a preliminary study of specific antisera that react against intracellular catalase of Candida sp. and neutralize the enzymatic activity. Further study is necessary to develop species-specific antibody once differences in the susceptibility of the Candida species to commonly used antifungal drugs make identification to the species level important.

Antisoros foram desenvolvidos em animais em resposta à injeção de antígenos intracelulares de Candida albicans, C. tropicalis e C. parapsilosis. A presença de catalase nos microrganismos tem sido relacionada à virulência, resistência a drogas e imunogenicidade. A catalase intracelular está sempre presente nas cepas de leveduras do gênero Candida e neste trabalho, sua atividade enzimática foi analisada por PAGE, após exposição aos antisoros obtidos. Verificou-se que as catalases de C. albicans, C. tropicalis e C. parapsilosis foram imunogênicas e apresentaram diferenças quanto à sua ligação aos anticorpos específicos produzidos nos coelhos. Testes de reação cruzada mostraram que quando o antisoro obtido do animal imunizado com C. albicans foi incubado com os extratos intracelulares de cada uma das três espécies, a atividade da catalase intracelular foi neutralizada em todos os casos. Entretanto, os antisoros obtidos da imunização com C. parapsilosis e C. tropicalis não afetaram a atividade da catalase de C. albicans; a catalase de C. albicans foi neutralizada somente pelo antisoro específico. O antisoro anti-C. tropicalis foi espécie-específico e não reagiu com as catalases de C. albicans e C. parapsilosis. As atividades das catalases bovina e de Aspergillus niger não foram afetadas por nenhum dos antisoros produzidos contra Candida sp. Este trabalho é uma análise preliminar de antisoros específicos reagentes com a catalase intracelular de Candida sp., capazes de neutralizar a atividade enzimática. Novos estudos são importantes para o desenvolvimento de anticorpo espécie-específico, uma vez que diferentes espécies de Candida apresentam diferente susceptibilidade aos antifúngicos de uso corrente.

Catalase activity of different Candida species after exposition to specific antiserum.

Antisera were developed in rabbits after challenge with intracellular antigens of Candida albicans, C. tropicalis and C. parapsilosis. Microorganism catalase has been correlated with virulence, resistance to drugs and immunogenicity. The intracellular catalase is consistently present in strains of Candida and in this paper, the enzyme activity was analysed by PAGE after exposition to antisera. The catalases of C. albicans, C. parapsilosis and C. tropicalis were immunogenic and differed in their binding to specific antibodies raised in rabbits. Tests of cross-reactivity between different Candida species showed that when antiserum from C. albicans immunized rabbit was incubated with intracellular extracts of these three Candida species, the catalases activities were abolished. However, the antisera from C. parapsilosis or C. tropicalis immunized rabbits did not affect the catalase activity of C. albicans; the enzyme of C. albicans was inactivated only by the antiserum to the catalase of own C. albicans. The antiserum to the catalase of C. tropicalis was species-specific and did not cross-react with catalases of C. albicans and C. parapsilosis. The activities of Aspergillus niger and bovine catalases were not affected by the antiserum from any Candida immunized rabbits. This report is a preliminary study of specific antisera that react against intracellular catalase of Candida sp. and neutralize the enzymatic activity. Further study is necessary to develop species-specific antibody once differences in the susceptibility of the Candida species to commonly used antifungal drugs make identification to the species level important.

"Beijerinckia derxii" stimulates the viability of non-N(2)-fixing bacteria in nitrogen-free media

The interactions between the nitrogen-fixing microorganism "Beijerinckia derxii" with two non-diazotrophic bacteria, either "Escherichia coli" or a faculty sulphur-oxidizing chemolitroph, were studied in mixed cultures. Direct and indirect contact between "B. derxii" and "E. coli" were tested. "B. derxii" increased CFU numbers and/or maintained the viability of the non-diazotrophic bacteria, but neither growth nor nitrogenase activity of the nitrogen-fixing bacterium were affected by either partner