Identificação e caracterização do gene nifH em bactérias isoladas do solo de cangas na região de Corumbá, Mato Grosso do Sul

Abstract

The excessive use of artificial inputs and fertilizers in agriculture has contributed to environmental degradation, with impacts on the soil and microbiota, altering their physical, chemical and biological properties. In Brazil, one of the largest agricultural producers in the world, the consumption of pesticides and biocides is increasing, which aggravates these effects, in some cases making the soil unproductive. Among the most important components of the soil is nitrogen, an essential element for life, which is fixed by microorganisms, especially bacteria, which convert atmospheric nitrogen (N₂) into forms that can be assimilated by plants. The nitrogen fixation process is mediated by the nitrogenase enzyme, synthesized from the nifH gene, which is widely used as a molecular marker for ecological studies of biological nitrogen fixation. Cangas are a type of ferruginous rock formation with ecological relevance due to their extreme environmental conditions, such as high temperature range, soil scarcity and water deficit. The bacterial diversity of the bromeliad rhizosphere that occurs in the cangas of the Urucum Residual Plateau inspired the present study, which sought to identify the presence of the nifH gene in bacteria isolates from this region. A total of 59 bacterial isolates were selected, 21 of which tested positive for the nifH gene and were subsequently sequenced. Bioinformatics analyses of these sequences were used to classify the isolates taxonomically and generate a phylogenetic tree, with the aim of understanding the diversity and nitrogen-fixing potential of these bacteria in an endemic environment. Of the 21 samples positive for the nifH gene, eight bacterial genera were identified, including: Acinetobacter, Alcaligenes, Bacillus, Brevibacterium, Paenibacillus and Staphylococcus. These genres are recognised as potential nitrogen fixators, highlighting themselves by their promising role in biopertilization and in the promotion of more sustainable agricultural practices.