Potencial biotecnológico de actinobactérias do semiárido nordestino na busca por novos agentes antimicrobianos

Abstract

Actinobacteria constitute a group of filamentous microorganisms of significant ecological and biotechnological relevance, widely recognized for their ability to synthesize a vast array of secondary metabolites, including industrial enzymes and antimicrobial agents. Although the genus Streptomyces is the most prominent in the literature overall, the so-called rare actinobacteria comprising morphologically and phylogenetically distinct genera emerge as promising sources for the discovery of new bioactive compounds, as they are less explored and consequently may possess unknown mechanisms, such as biosynthetic pathways for metabolites with antimicrobial activity. In this context, the present study aimed to isolate and characterize the antimicrobial potential of 16 strains of rare actinobacteria, designated as AU (Ubajara Actinobacteria), originating from soil samples of the Caatinga biome in the semi-arid Northeast of Brazil. Initial antimicrobial screening conducted using the cross-streak technique against the pathogens Staphylococcus aureus (ATCC 25923), Salmonella enterica (ATCC 14028), and Klebsiella pneumoniae (ATCC 10031) revealed that four of these strains (AU-1, AU-2, AU-8, and AU-11), corresponding to 25% of the total, exhibited promising inhibitory profiles. These strains were then subjected to fermentation assays under standard conditions and in co-culture, followed by the collection of their cell-free supernatants (CFSs), obtained by centrifugation of the fermented broths. The collected CFSs were reassessed for their antimicrobial potential using the well diffusion method - a more specific step in which only strains AU-2 and AU-8 maintained their antimicrobial activity, with AU-2 demonstrating a notable broadening of its spectrum of action against the tested pathogens. The obtained results not only validate the biotechnological potential of the semi-arid microbiota but also highlight strain AU-2 as a particularly robust candidate for future studies aimed at identifying, purifying, and characterizing the bioactive compounds responsible for its activity, reinforcing the strategic importance of prospecting actinobacteria, especially rare ones, in unique biomes.