Phenotypic and genotypic analysis of heterotrophic bacteria and nitrogen-fixing in sediment in the basin of the Cuiaba River – MT

Abstract

Sediments are complex systems that are affected by geological, hydrodynamic, chemical and biological parameters, as determined by interactions between the sedimentary environments of each region. This study aimed to characterize the diversity of total heterotrophic bacteria and nitrogen fixers in Cuiabá River sediments using conventional techniques of microbiology and molecular biology. Sediment samples were collected bimonthly from four points: Cuiabazinho, Passagem da Conceição, Ribeirão Cocais and Barão de Melgaço. The samples were processed in serial dilutions (10-2 to 10-7) in 0.85% saline solution. They were then cultured in Petri dishes using the Spread Plate technique in the Trypic Soy Agar (TSA) culture medium for total heterotrophic bacteria and selective medium (NFB, JMV and culture median 79) incubated at 35°C for nitrifying bacteria. The bacterial strains were then re-isolated on Nutrient Agar (NA) in order to obtain a pure culture for the Gram analysis morphotypes. This test revealed that, of the 202 bacterial isolates, 59 % were positive rods. The largest bacterial count was obtained in the TSA medium, as compared to other means of culture. The profile of the bacterial community showed that most, or 28 %, of the bacteria were of the Bacillaceae family and these were used for molecular analysis using Box-PCR, which showed a great diversity of species. These results indicate the importance of microbial diversity research in sediments in Mato Grosso State using molecular techniques.