The zoonotic pathogen Leptospira interrogans mitigates environmental stress through cyclic-di-GMP-controlled biofilm production

Roman Thibeaux,Marie-Estelle Soupé-Gilbert,Mathieu Picardeau,Cyrille Goarant,Nicolas Eskenazi,Heike Bähre,Joëlle Vinh,Emilie Bierque,Anthony Douyère,Dominique Girault,Julien Fernandes,Malia Kainiu

doi:10.1038/s41522-020-0134-1

Abstract

The zoonotic bacterium Leptospira interrogans is the aetiological agent of leptospirosis, a re-emerging infectious disease that is a growing public health concern. Most human cases of leptospirosis result from environmental infection. Biofilm formation and its contribution to the persistence of virulent leptospires in the environment or in the host have scarcely been addressed. Here, we examined spatial and time-domain changes in biofilm production by L. interrogans. Our observations showed that biofilm formation in L. interrogans is a highly dynamic process and leads to a polarized architecture. We notably found that the biofilm matrix is composed of extracellular DNA, which enhances the biofilm’s cohesiveness. By studying L. interrogans mutants with defective diguanylate cyclase and phosphodiesterase genes, we show that biofilm production is regulated by intracellular levels of bis-(3′–5′)-cyclic dimeric guanosine monophosphate (c-di-GMP) and underpins the bacterium’s ability to withstand a wide variety of simulated environmental stresses. Our present results show how the c-di-GMP pathway regulates biofilm formation by L. interrogans, provide insights into the environmental persistence of L. interrogans and, more generally, highlight leptospirosis as an environment-borne threat to human health.

Highlights

Pathogenic species of bacteria from the genus Leptospira cause leptospirosis, a zoonosis that has been observed worldwide but is especially prevalent in tropical low-income countries[1]
The c-di-GMP pathway is known to be regulated during biofilm formation by Leptospira biflexa[43]
By pathogenic L. interrogans to create resilient biofilms and synthesis or degradation, we demonstrated that impaired c-diprotect itself against extracellular stresses

Summary

INTRODUCTION

Pathogenic species of bacteria from the genus Leptospira cause leptospirosis, a zoonosis that has been observed worldwide but is especially prevalent in tropical low-income countries[1]. Studies of reservoir mammals have highlighted the presence of bacterial aggregates within the lumen of proximal renal tubules[12,13]. These aggregates share some morphological features with biofilms, which might explain why Leptospira are so persistent and why antibiotic treatments fail to clear the bacteria from the kidneys[14]. C-di-GMP is produced by diguanylate cyclases (DGCs) and degraded by phosphodiesterases (PDEs)[25,26] Production of this intracellular signalling molecule is low in motile cells whereas its elevation in the cytoplasm triggers biofilm formation[27,28].

RESULTS

Weeks c 80

DISCUSSION

Findings

METHODS