Identificação e bioatividade de microrganismos fotossintetizantes do Parque Nacional da Chapada das Mesas-MA

Abstract

Cyanobacteria and microalgae form a very diverse group and exhibit morphological, biochemical and physiological differences. They are primary producers of a rich source of bioactive secondary compounds. This study aims to identify the genera of cyanobacteria and microalgae present in the water bodies of the Chapada das Mesas National Park and verify their bioactivity. The pH, temperature, turbidity and dissolved oxygen parameters, as well as the presence of nutrients such as ammonia, nitrites, nitrates, and phosphates, were measured in parallel with the samples obtained at 12 different points in the Chapada das Mesas National Park. Samples were sent to the pharmacognosy 2 laboratory of the Federal University of Maranhão for cultivation and isolation. The samples were cultured in BG-11 medium with nitrogen. After the growing period, slides of each culture were prepared aseptically for microscopic observation, and different techniques of isolation were applied in order to obtain unialgal cultures. Identification keys of microalgae and cyanobacteria were used for the morphological identification. Morphological analysis evidenced the presence of two genera of cyanobacteria (Synechococcus and Geminocystis) and a genus of microalgae (Chlorella). These observations were confirmed by molecular identification and ultrastructure analysis using atomic force microscopy. Regarding the bioactivity of the studied strains, no activities were observed on the Rhipicephalus microplus organism. Similarly, the antimicrobial activity test showed no halo of inhibition against the tested microorganisms. It is known that the negative results observed are not decisive, other growth conditions of the strains, as well as, different concentrations of the extracts should be tested. The cytotoxicity test performed against the microcrustacean Artemia salina showed a 50% mortality rate for the strain GBBB 06 (Chlorella). This study shows that polyphase approaches are an excellent resource for the complete and reliable identification of microorganisms, including ultrastructural, morphological, physiological and molecular analysis data. In addition, it showed that PNCM contains interesting photosynthetic microorganisms according to the current literature. It is suggested to continue studies aimed at elucidating of their microbial community.