Abstract
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.
Highlights
In recent decades, new challenges have arisen for the pharmaceutical and food industries regarding the fight against pathogenic microorganisms and spoilage
The sequence of the 16S rRNA gene was compared with sequences similar to those of reference microorganisms, using the National Center for Biotechnology Information (NCBI) Basic Local Alignment Search Tool (BLAST)
The gene sequence of Bacillus sp. sed 1.4 was submitted to Standard Nucleotide BLAST with the access code MH666076
Summary
New challenges have arisen for the pharmaceutical and food industries regarding the fight against pathogenic microorganisms and spoilage. The challenges are even greater due to the emergence of antimicrobial resistance, which due to selective pressure, causes microorganisms to no longer respond to the usual antimicrobial drugs (Devatkal et al 2014, Choi et al 2019) In this view, exploring new antimicrobial substances has become an object of intensive investigation. The sporulation and rapid growth, which are characteristic of the genus Bacillus, mean significant advantages in terms of survival in different habitats This is the reason for the research on their ability to produce bioactive substances (Ebrahimipour et al 2014, Dimkic et al 2017, Beltran et al 2018, Zhao et al 2018). Bacillus has industrial applications due to its easy genetic manipulation, favorable cultivation characteristics on a large scale and the ability to secrete GRAS status proteins (“Generally Recognized As Safe”) (Zhang et al 2020)
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