COPPER HOMEOSTASIS IN Mycobacterium africanum L6: THE ROLE OF mymT AND bglS GENES

• Grant number: 25/15102-0
• Support Opportunities: Scholarships abroad - Research Internship - Doctorate (Direct)
• Start date: January 05, 2026
• End date: November 29, 2026
• Field of knowledge: Biological Sciences - Microbiology - Biology and Physiology of Microorganisms
• Principal Investigator: Ana Marcia de Sá Guimarães
• Grantee: Kevim Bordignon Guterres
• Supervisor: Katerina Heran Darwin
• Host Institution: Instituto de Ciências Biomédicas (ICB). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Institution abroad: New York University, United States
• Associated to the scholarship: 23/07582-7 - Influence of copper on the appearance of antimicrobial persistence or tolerance in Mycobacterium tuberculosis and Mycobacterium africanum, BP.DD

Abstract

Tuberculosis (TB) remains one of the leading causes of morbidity and mortality worldwide. While most cases are caused by Mycobacterium tuberculosis (Mtb), up to 50% of TB infections in West Africa are attributed to Mycobacterium africanum (Maf), particularly lineage 6 (MafL6). This lineage is characterized by slow growth, reduced virulence, and attenuated immune responses, in addition to specific metabolic features that distinguish it from Mtb. However, the genetic mechanisms underlying these differences remain poorly understood.The Region of Difference 702 (RD702), which is present in Mtb and other lineages but absent in MafL6, affects two adjacent genes: mymT and bglS. The mymT gene encodes a metallothionein involved in copper (Cu) homeostasis, a key factor in resistance to metal-induced toxicity during infection. The bglS gene encodes a putative ¿-glucosidase, whose function remains unclear, but may be related to adaptation to environmental stress and cell wall integrity.Previous transcriptomic data from our group demonstrated that MafL6 displays a copper stress response even at Cu concentrations that are non-toxic to Mtb. In vitro phenotypic assays confirmed that MafL6 is significantly more sensitive to Cu than both Mtb and MafL5, showing distinct alterations in the lipid composition of the cell envelope upon exposure to the metal. It is hypothesized that the RD702 deletion and the resulting functional loss of mymT and bglS are directly associated with this phenotype.This project aims to elucidate the role of mymT and bglS genes in copper resistance and the virulence of MafL6. To this end, we propose to restore these genes-individually and in combination-using the integrative plasmid pMC1s, with and without their native promoters. Recombinant strains will be evaluated for copper sensitivity under various concentrations using solid media assays.Additionally, the strains exhibiting the highest copper resistance will be selected for evaluation in a murine model of chronic TB infection (C57BL/6 mice), assessing bacterial burden, lung histopathology, cytokine profiles, and immune cell composition via flow cytometry. It is expected that the reintroduction of mymT and/or bglS will lead to a phenotype more similar to Mtb, with enhanced copper resistance and modulation of the host immune response.This study will contribute significantly to the understanding of MafL6 pathophysiology by providing insights into metal stress adaptation mechanisms and potential virulence determinants specific to this lineage.