Cpn60.1 (GroEL1) Contributes to Mycobacterial Crabtree Effect: Implications for Biofilm Formation.

Sheng Zeng,Dong Yang,Alain Baulard,Ruddy Wattiez,Mamadou Daffé,Philippe Lefèvre,Patricia Constant,Véronique Fontaine

doi:10.3389/fmicb.2019.01149

Abstract

Biofilm formation is a survival strategy for microorganisms facing a hostile environment. Under biofilm, bacteria are better protected against antibacterial drugs and the immune response, increasing treatment difficulty, as persistent populations recalcitrant to chemotherapy are promoted. Deciphering mechanisms leading to biofilms could, thus, be beneficial to obtain new antibacterial drug candidates. Here, we show that mycobacterial biofilm formation is linked to excess glycerol adaptation and the concomitant establishment of the Crabtree effect. This effect is characterized by respiratory reprogramming, ATP downregulation, and secretion of various metabolites including pyruvate, acetate, succinate, and glutamate. Interestingly, the Crabtree effect was abnormal in a mycobacterial strain deficient for Cpn60.1 (GroEL1). Indeed, this mutant strain had a compromised ability to downregulate ATP and secreted more pyruvate, acetate, succinate, and glutamate in the culture medium. Importantly, the mutant strain had higher intracellular pyruvate and produced more toxic methylglyoxal, suggesting a glycolytic stress leading to growth stasis and consequently biofilm failure. This study demonstrates, for the first time, the link between mycobacterial biofilm formation and the Crabtree effect.

Highlights

Bacterial biofilms are multicellular communities comprising inhabitant cells and surrounding extracellular matrix (Hassanov et al, 2018)
The role of Cpn60.1 on mycobacterial biofilm growth was mainly established in M. smegmatis (Ojha et al, 2005)
Loss of only phthiocerol dimycocerosates (PDIM) had a negligible effect on mycobacterial biofilm formation, absence of both lipids reduced the biofilm maturation (Figure 1B). These results suggested a role for PDIM/phenolic glycolipids (PGL) in mycobacterial biofilm maturation

Summary

Introduction

Bacterial biofilms are multicellular communities comprising inhabitant cells and surrounding extracellular matrix (Hassanov et al, 2018). The biofilm-inhabiting bacteria are believed to be heterogeneous with regard to their physiology and metabolism, contributing to the survival of the biofilm community under challenging external stresses such as antibiotics (Stewart and Franklin, 2008; Moormeier et al, 2013; Liu et al, 2015; Hassanov et al, 2018). As a result of metabolic adaptations, bacteria may produce some metabolites that can subsequently function as biofilm-regulating metabolic signals This is illustrated, for example, in Pseudomonas aeruginosa biofilms requiring pyruvate fermentation to produce lactate (Petrova et al, 2012) and by the fact that acetic acid was shown to act as a biofilm-stimulating volatile metabolite in Bacillus subtilis (Chen et al, 2015). A better understanding of these metabolic shifts could help to identify vulnerable targets

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