Insetos e microrganismos : interações positivas e negativas como abordagem para a prospecção de produtos biotecnológicos

Abstract

Insects, bacteria and fungi are megadiverse groups that interact in practically all terrestrial environments, with implications to human life. We start from positive and negative interactions between insects and microbes to prospect for microorganisms with biotechnological applications. Approaching negative interactions, we prospect Bacillus bacteria able to kill Aedes aegypti mosquito larvae. We obtained four isolates (Bacillus safensis BacI67, Bacillus paranthracis C21, Bacillus velezensis B15 and B64a) producing supernatants and lipopeptides toxic to the larva but safe to model organisms such as Caenorhabditis elegans, Galleria mellonella, Tetrahymena pyriformis and Chlorella vulgaris. We assembled and mined the genomes of the four bacteria and found clusters for lipopeptides, terpenes, and other molecules that may be accountable for the larvicidal action. Approaching positive interactions, we studied the intestinal microbiota of the larva of a Rutelinae beetle - Pelidnota luridipes - that lives in decomposing wood by dependent and independent cultivation methods. We isolated 272 and 29 bacterial isolates and yeasts identified in 57 and 7 species, respectively. Using metabarcoding, we found 1,481 and 267 OTUs of bacteria and fungi, respectively. Microbiota of midgut and hindgut is distinguished by the composition and abundance of bacteria and fungi, with a tendency for greater richness and diversity of yeasts in the anterior chamber, and the opposite for bacterial communities. We isolated microbes able to produce several enzymes - which can help the insect to survive on a nutritionally weak diet. Among the isolates, Apiotrichum siamense L29A and Bacillus sp. BL17B hadprobiotic and antibacterial activity in vitro and protected Galleria mellonella moth larvae against infection by the pathogens Listeria monocytogenes ATCC19111 and Pseudomonas aeruginosa ATCC 9027. This is the first work with the larval microbiota Rutelini, demonstrating its diversity and potential for prospection of microbial products like probiotics. This work shows that the interactions between microorganisms and insects are an important starting point for the search and development of biotechnological products.