Dinâmica de quorum sensing e produção de violaceína em cocultivos de Chromobacterium subtsugae e Bacillus

Abstract

Microbial communication plays a critical role in regulating collective behaviors, such as the production of secondary metabolites, including pigments with bioactive properties. In Chromobacterium subtsugae, violacein synthesis is regulated by quorum sensing (QS) mechanisms that modulate gene expression in response to bacterial population density. This communication can be influenced by interspecies interactions, such as cocultivation with other bacterial species, which may act as inducers or inhibitors of QS-related gene expression. In this context, the influence of microbial interactions on violacein synthesis was investigated, beginning with a systematic literature review followed by experimental coculture assays. The first chapter, through the systematic review, identified the key genes involved, notably cviI, cviR, and the vioABCDE operon, and showed molecules and quorum sensing interference strategies, highlighting their potential biotechnological applications. In the second chapter, experimental assays demonstrated modulation of violacein production in C. subtsugae ATCC31532 when cocultured with various Bacillus species, particularly B. thuringiensis subsp. kurstaki. Interspecies microbial competition influenced pigment biosynthesis. Scanning electron microscopy revealed morphological changes and the presence of Cry crystals in cocultures with B. thuringiensis, indicating competitive responses. Four cultivation conditions were tested: isolated C. subtsugae (CS), sequential coculture first inoculated with C. subtsugae followed by B. thuringiensis subsp. kurstaki after 24 hours (CS + BTK), inverse coculture with initial inoculation of B. thuringiensis subsp. kurstaki followed by C. subtsugae (BTK + CS), and simultaneous coculture of both species (CB). The CS + BTK treatment showed the highest increase in violacein production compared to monoculture, while the BTK + CS and CB conditions yielded levels similar to the control. These findings suggest that the temporal dynamics of bacterial interactions directly influence quorum sensing modulation and secondary metabolite biosynthesis, providing a foundation for developing strategies to optimize the production of bioactive compounds with pharmaceutical and industrial relevance.