Características de bactérias naturalmente estabelecidas em solos de manguezal contaminados por mercúrio

Abstract

Mangroves act important role in environment because operate as mitigating place in case of environmental disasters such as storms or erosion. These ecosystems are an important spawning area and nursery for marine biota. Beyond that, acts as key role in carbon capture and have a wide microbial diversity. Despite that importance, mangroves ecosystems have been adversely affected by human activities, primarily the high load of organic and inorganic contaminants. These activities are responsible for changes in the physical-chemical, geochemical and biological parameters of this ecosystem. The soil samples used in this study (P1 and P2) were collected in the mangrove swamp of the Botafogo River estuary, located in Itamaracá, Pernambuco, Brazil. This estuary has the worst mercury contamination rates recorded on the entire Brazilian coast, this pollution was caused by improper waste disposal from an old chlorine-soda factory installed in the region, named Brazilian agrochemical (Agroquímica do Brasil). Soil sample collection were analyzed in laboratory and provided results of pH levels, Eh (redox potential), Soil Organic Matter (SOM) and Granulometry. The purpose of the research is to isolate and morphologically characterize bacteria from soils contaminated with mercury (Hg) collected in the Botafogo River estuary. And, in addition, to test the resistance of these Bacterial isolation to different concentrations of inorganic mercury (Hg) in culture media. For this, the process of isolation of bacteria was adopted in selective rich medium with Hg, in the form of HgCl2, in doses 0; 2.5; 5; 10; 50 and 100 mg L-1. Luria-Bertani broth was adopted in this study. As a result, a total of 115 isolation were obtained, which were submitted to morphological and molecular characterization and gram stain. Bacterial strain resistant to a concentration of 100 mg L-1 of iHg in solid medium (11 isolation) were submitted to minimal inhibitory concentrations (MICs) tests, resulting in MICs between 50 and 100 mg L-1. The strains that showed the highest MICs were isolated from the soil sample with the highest Hg concentrations. The isolation most resistant to iHg were identified based on the 16S rRNA region and showed greater similarity to the genus Enterococcus, Bacillus and Pseudomonas.