Caracterização de microorganismos com potencial biotecnológico no mangue de pedra Búzios-RJ

Abstract

The mangroves are coastal ecosystems found in tropical and subtropical regions. Due to their high productivity, they are crucial for biodiversity. They are associated with the mouths of watercourses such as rivers, estuarine deltas, and the sea, subject to tidal fluctuations. Mangrove soils are unique, with distinct physicochemical characteristics, rich microbial biodiversity, and biotechnological potential. The region surrounding plant roots, the rhizosphere, is a dynamic environment with complex interactions between microorganisms and plants, promoting nutrient recycling, carbon fixation, and resistance to environmental stresses. In the city of Armação dos Búzios, Rio de Janeiro, there is a rare mangrove of global significance known as Mangue de Pedra, which develops on rocky soil without a river. Freshwater supply is provided by the emergence of rainwater from an underground aquifer that mixes with seawater along a narrow strip of sand and rock at Beach of the Gorda. In this rare and understudied scenario, understanding the microbial diversity and biotechnological potential of bacteria and arbuscular mycorrhizal fungi (AMF) associated with the rhizosphere is essential. Identifying these microorganisms is challenging due to morphological variety and intra-specific variation. Molecular tools are essential for understanding this diversity and its biotechnological potential. Therefore, the objective of this study was to evaluate the microbial diversity of AMF and bacteria in the rhizospheric sediment and plant roots in Mangue de Pedra, Búzios, Rio de Janeiro, Brazil, aiming to explore the biotechnological potential of these microorganisms. Water samples from four points in the mangrove were collected for nutrient analysis (nitrite, nitrate, phosphate, and ammonium), and rhizosphere and root samples were collected for morphological and molecular microbiological analyses. For AMF, nucleic acids were extracted using the DNeasy PowerSoil Pro Kit, and the 18S rRNA gene region was analyzed by PCR using universal fungal genes (NS1/NS4) and Glomeromycota-specific genes (AML1/AML2), followed by Sanger sequencing. Additionally, AMF spores found in the rhizosphere were morpho-taxonomically identified under a microscope. For bacterial analysis, pure colony isolation was initially performed in Tryptone Soy Broth, followed by DNA extraction using the Wizard™ SV Genomic DNA Purification System. PCR and Sanger sequencing of the 16S rRNA gene region were then conducted. Eleven bacterial genera were identified, belonging to the phyla Actinomycetoma, Deferribacteriota, Bacillota, Pseudomonadota, and Proteobacteria. Five AMF species were also identified, including species with biotechnological potential for hydrocarbon and heavy metal bioremediation (Paraglomus occultum, Acaulospora spinosa, Funneliformis mosseae, Scutellospora calospora, and Acaulospora cavernata). The absence of AMF in the roots of the only recent young specimen of Rhizophora mangle in this mangrove suggests a possible lack of mycorrhizal colonization. This pioneering microbiological research in the region highlights the need for further investigation into microorganisms with biotechnological potential and microbial diversity in other mangroves with similar sediments.