Understanding the ant-bacteria symbiosis using chemical and genetic tools

Author(s)

Taise Tomie Hebihara Fukuda

• Document type: Doctoral Thesis
• Press: Ribeirão Preto.
• Institution: Universidade de São Paulo (USP). Faculdade de Ciências Farmacêuticas de Ribeirão Preto (PCARP/BC)
• Defense date: 2022-05-06

Examining board members

Monica Tallarico Pupo; Roberto Gomes de Souza Berlinck; Marcio Vinícius Bertacine Dias; Alessandra da Silva Eustaquio

• Advisor: Monica Tallarico Pupo

Abstract

This thesis was divided into three chapters, according to the symbiosis studied and the approaches used in such studies: Chapter I refers to the review on interactions between social insects and microorganisms mediated by chemical compounds; Chapter II refers to the chemical and evolutionary study of Pseudomonas spp. in the Cecropia-Azteca interaction; and Chapter III, to the study of Attine ants from a chemical and biogeographic point of view. Chapter I discusses the state of the art of natural products research guided by chemical ecology, focusing on the symbiosis between microbes and fungus-growing ants, stingless bees, termites and wasps. In Chapter II, we studied the Cecropia-Azteca symbiosis, in which the ant defends the plant from external aggressors and the plant provides shelter to the ant colony. A Pseudomonas isolate had its genome sequenced and analyzed. This strain carries a biosynthetic gene cluster (BGC) that encodes the production of a cyclic lipodepsipeptide. This BGC shows mutations that may be related to the loss of function of condensation domains that would also be responsible for the epimerization of the upstream amino acid in the assembly line. The determination of the specificity of adenylation domains through phylogenetic analysis does not have sufficient resolution for the prediction of the final peptide. Thus, the cyclic lipodepsipeptide was isolated and its structure was determined, corresponding to viscosinamide. The fact that this compound has antifungal activity added to the inhibitory profile of Pseudomonas strains suggests the ecological relevance of this genus of bacteria in the chemical defense of the Cecropia-Azteca symbiosis. In the third part, studies were carried out on fungus-growing ants collected in different places in Brazil, including the Amazon Forest, Atlantic Forest and Cerrado. The symbiosis between Attine ants and actinobacteria strains was studied. This study focuses on Pseudonocardia, which can produce metabolites used by the ants to defend themselves against specialized fungal pathogens. Metabolomic analysis (LC - MS) in several Pseudonocardia strains revealed that a significant number of strains produced a new compound named attinimicin. Its biosynthesis pathway was identified, which has an evolutionary relationship with other previously characterized non-ribosomal peptides. Furthermore, attinimicin shows potent in vivo antifungal activity, but insignificant activity in vitro. Its biological activity is restricted to the absence of iron. Thus, the constant of iron chelation was determined by calculating pFeIII and analyzes were carried out comparing the affinity for complexation with other metals, with attinimicin showing greater affinity towards iron. The geographic distribution of attinimicin, restricted only to the Brazilian territory, distinguishes it from other metabolites that were previously identified from this same system. (AU)

• FAPESP's process: 15/26349-5 - Chemical and ecological study of microorganisms associated with the symbiosis Cecropia-Azteca
• Grantee: Taise Tomie Hebihara Fukuda
• Support Opportunities: Scholarships in Brazil - Doctorate (Direct)