Characterization of the antimicrobial activity produced by Bacillus sp. isolated from wetland sediment.

Bacteria of the genus Bacillus sp. present the potential for inhibiting various pathogens, making them a promising starting point in the search for new antimicrobial substances. In this study, bacteria were isolated from sediment samples from humid areas of a Natural Conservation Unit in the state of Rio Grande do Sul, Brazil. The isolate Bacillus sp. sed 1.4 was selected for production of antimicrobial activity, and was characterized by MALDI-TOF and 16S rDNA sequencing. Phylogenetic analysis showed that Bacillus sed 1.4 was closely related to Bacillus altitudinis and Bacillus pumilus. The cell-free supernatant was partially purified using ammonium sulfate precipitation, gel filtration chromatography (Sephadex G-200) and an ultrafiltration membrane. Partial purification resulted in specific activity of 769.23 AU/mg, with a molecular mass of approximately 148 kDa. This antimicrobial substance showed stability at 100°C for 5 min, and was inactivated by proteolytic enzymes. An antimicrobial effect against Listeria species was observed. Considering the importance of the Listeria genus in the area of food safety, this antimicrobial activity should be further explored, specifically in the field of dairy products and with a focus on food biopreservation studies.

Biological activity of bacteria isolated from wetland sediments collected from a conservation unit in the southern region of Brazil.

Wetlands are ecosystems rich in biodiversity and their ecological importance is recognized worldwide. Sediment samples were subjected to physical-chemical analysis and organic carbon content varied from 3.0% to 4.8%, the clay between 32 and 40%, silt with 41% and 43%, sand coarse varied between 6 and 11% and fine sand between 7 and 16%. The nitrogen values ​​varied from 0.25% to 0.48%, the pH from 5.4 to 7.5 and the humidity ​​varied from 44 to 56%. The selected isolates were evaluated for enzymatic properties and 64% showed positive results for amylase, 16% for gelatinase, 37% for lipase, 91% for protease and 2.7% for inulinase. Six bacterial isolates were selected for the overlapping assay and Bacillus sp. sed 2.2 showed inhibitory activity against Corynebacterium fimi NCTC 7547, and the antimicrobial substance was partially purified. The characterization of the substance was carried and the substance was stable at 100° C for up to 10 minutes and sensitive to the enzymes papain and trypsin. This substance was active against some species of Listeria, including Listeria monocytogenes ATCC 7644. The microorganims obtained from sediment samples were important sources of bioactive compounds, including enzymes and peptides, being a source of bioactive compounds to be studied.