Unexplored biosynthetic gene clusters in bacteria isolated from Brazilian stingless bee honey with activity against...

The emergence of new infectious diseases and the development of microbial resistance to existing drugs, accompanied by a decline in the discovery of new antibiotic classes through traditional approaches, highlight the urgent need for novel strategies and sources of bioactive compounds. We focused on a little explored environment for bioprospecting microorganisms with rich specialized metabolites: honey produced by native Brazilian stingless bees. We thus isolated 378 microorganisms from commercial honeys from 11 species of Brazilian bees. After microbial isolation, we screened for their antibiotic activity using the laboratory Escherichia coli DH5α strain. One hundred selected isolates were further tested against five ATCC strains including ampicillin-resistant E. coli (30% active), methicillin- and oxacillin-resistant Staphylococcus aureus (61%), and vancomycin-resistant Enterococcus faecalis (25%). Additional assays against Klebsiella pneumoniae, including the multidrug-resistant (MDR) strain BAA-2146, identified two isolates active against the most threatening pathogenic strain. We performed molecular identification of promising isolates, based on the partial sequence of the 16S rRNA gene region. Most of the isolates were identified as Bacillus spp., but Streptomyces and Aureimonas species were also among the prospected strains. We performed whole genome sequencing of the two isolates active against MDR K. pneumoniae: a potential new species Bacillus and a Shouchella rhizosphaerae M12-28. Through genome mining, we identified a variety of previously uncharacterized biosynthetic gene clusters, highlighting the potential of Brazilian stingless bees microbiota as a source of novel antibiotic compounds to address the global MDR crisis.