Protozoans bacterivory in a subtropical environment during a dry/cold and a rainy/warm season

In aquatic ecosystems, bacteria are controlled by several organisms in the food chain, such as protozoa, that use them as food source. This study aimed to quantify the ingestion and clearance rates of bacteria by ciliates and heterotrophic nanoflagellates (HNF) in a subtropical freshwater reservoir (Monjolinho reservoir -São Carlos -Brazil) during one year period, in order to verify their importance as consumers and controllers of bacteria in two seasons, a dry/cold and a rainy/warm one. For this purpose, in situ bacterivory experiments were carried out bimonthly using fluorescently labeled bacteria with 5-(4,6 diclorotriazin-2yl) aminofluorescein (DTAF). Although ciliates have shown the highest individual ingestion and clearance rates, bacterivory was dominated by HNF, who showed higher population ingestion rates (mean of 9,140 bacteria h-1mL-1) when compared to ciliates (mean of 492 bacteria h-1mL-1). The greater predation impact on bacterial communities was caused mainly by the small HNF (< 5 µm) population, especially in the rainy season, probably due to the abundances of these organisms, the precipitation, trophic index state and water temperature that were higher in this period. Thus, the protozoan densities together with environmental variables were extremely relevant in determining the seasonal pattern of bacterivory in Monjolinho reservoir.

Evaluating methods for the isolation of marine-derived fungal strains and production of bioactive secondary metabolites

In the present investigation we evaluate methods for the isolation and growth of marine-derived fungal strains in artificial media for the production of secondary metabolites. Inoculation of marine macroorganisms fragments in Petri dishes proved to be the most convenient procedure for the isolation of the largest number of strains. Among the growth media used, 3% malt extract showed the best result for strains isolation and growth, and yielded the largest number of strains from marine macroorganisms. The percentage of strains isolated using each of the growth media which yielded cytotoxic and/or antibiotic extracts was in the range of 23-35%, regardless of the growth media used. Further investigation of extracts obtained from different marine-derived fungal strains yielded several bioactive secondary metabolites, among which (E)-4-methoxy-5-(3-methoxybut-1-enyl)-6-methyl-2H-pyran-2-one is a new metabolite isolated from the Penicillium paxilli strain Ma(G)K.

Antibiotic, cytotoxic and enzyme inhibitory activity of crude extracts from Brazilian marine invertebrates

Herein we present the results of a screening with 349 crude extracts of Brazilian marine sponges, ascidians, bryozoans and octocorals, against 16 strains of susceptible and antibiotic-resistant bacteria, one yeast (Candida albicans), Mycobacterium tuberculosis H37Rv, three cancer cell lines MCF-7 (breast), B16 (murine melanoma ) and HCT8 (colon), and Leishmania tarentolae adenine phosphoribosyl transferase (L-APRT) enzyme. Less than 15 percent of marine sponge crude extracts displayed antibacterial activity, both against susceptible and antibiotic-resistant bacteria. Up to 40 percent of marine sponge crude extracts displayed antimycobacterial activity against M. tuberculosis H37Rv. Cytotoxicity was observed for 18 percent of marine sponge crude extracts. Finally, less than 3 percent of sponge extracts inhibited L-APRT. Less than 10 percent of ascidian crude extracts displayed antibacterial activity. More than 25 percent of ascidian crude extracts were active against M. tuberculosis and the three cancer cell lines. Only two crude extracts from the ascidian Polysyncraton sp. collected in different seasons (1995 and 1997) displayed activity against L-APRT. Less than 2 percent of bryozoan and octocoral crude extracts presented antibacterial activity, but a high percentage of crude extracts from bryozoan and octororal displayed cytotoxic (11 percent and 30 percent, respectively) and antimycobacterial (60 percent) activities. The extract of only one species of bryozoan, Bugula sp., presented inhibitory activity against L-APRT. Overall, the crude extracts of marine invertebrates herein investigated presented a high level of cytotoxic and antimycobacterial activities, a lower level of antibacterial activity and only a small number of crude extracts inhibited L-APRT. Taxonomic analysis of some of the more potently active crude extracts showed the occurrence of biological activity in taxa that have been previously chemically investigated. These...

No presente estudo apresentamos resultados da triagem biológica realizada com 349 extratos obtidos de esponjas marinhas, ascídias, briozoários e octocorais do Brasil, em testes contra 16 linhagens de bactérias comuns e resistentes à antibióticos, uma levedura (Candida albicans), Mycobacterium tuberculosis H37Rv, três linhagens de células tumorais MCF-7 (mama), B16 (melanoma murínico) e HCT8 (cólon), e de inibição da enzima adenina fosforribosil transferase de Leishmania tarentolae (L-APRT). Menos de 15 por cento dos extratos de esponja marinhas apresentaram atividade antibacteriana, contra linhagens resistentes ou não a antibióticos. Quase 40 por cento dos extratos de esponjas marinhas apresentaram atividade antimicobacteriana contra Mycobacterium tuberculosis H37Rv. Foi observada citotoxicidade para 18 por cento dos extratos de esponjas marinhas. Finalmente, menos de 3 por cento dos extratos de esponjas apresentaram atividade inibitória da enzima L-APRT. Menos de 10 por cento dos extratos de ascídias apresentaram atividade antibacteriana. Mais de 25 por cento dos extratos de ascídias apresentaram atividade contra M. tuberculosis e as três linhagens de células tumorais. Somente dois extratos obtidos da ascídia Polysyncraton sp. coletada em duas diferentes épocas (1995 e 1997) apresentaram atividade contra L-APRT. Menos de 2 por cento dos extratos de briozoários e octocorais apresentaram atividade antibacteriana, mas uma alta percentagem de extratos destes animais apresentaram atividades citotóxica (11 por cento e 30 por cento, respectivamente) e antimicobacteriana (60 por cento). O extrato de somente uma espécie de briozoário, Bugula sp., apresentou atividade inibitória da enzima L-APRT. A análise taxonômica de algumas espécies de invertebrados que forneceram alguns dos extratos mais ativos, indicou a ocorrência de atividade biológica em espécies pertencentes a grupos taxonômicos que já foram anteriormente investigados do ponto de vista...