Mycobacterial Biofilm Formation and Drug Tolerance

Mycobacterial biofilms are multicellular communities in which bacilli embed themselves within a self-produced extracellular matrix, leading to increased tolerance to frontline antibiotics. This matrix comprises a complex mixture of lipids, polysaccharides (notably cellulose), extracellular DNA and proteins, forming a physical barrier that impedes drug penetration and fosters phenotypic heterogeneity. Within these biofilms, subpopulations of metabolically slowed or non-replicating bacilli persist despite prolonged chemotherapy, contributing to treatment failure and disease relapse. Regulatory pathways involving second messengers such as cyclic di-GMP and nucleoid-associated factors orchestrate the switch from planktonic growth to biofilm lifestyle, promoting synthesis of specialised cell-wall lipids like keto-mycolic acids. Environmental cues including reductive stress further trigger polysaccharide-rich biofilm assembly. Understanding the molecular underpinnings of mycobacterial biofilm formation and its direct link to drug tolerance is essential to devise strategies that shorten therapy duration and improve global tuberculosis control.

Research from Nature Portfolio

Recent studies have demonstrated that cyclic di-GMP binds directly to the regulatory protein Lsr2, activating the expression of enzymes responsible for keto-mycolic acid synthesis and thereby reinforcing lipid-rich biofilm matrices. A pivotal investigation detected cellulose-containing biofilms of Mycobacterium tuberculosis in infected lungs of animal models and clinical specimens, establishing a clear association between in vivo biofilm formation, evasion of host immunity and phenotypic drug tolerance; adjunctive treatment with nebulised cellulase enhanced the efficacy of isoniazid and rifampicin in murine infection. Foundational research has also shown that intracellular thiol reductive stress induces the rapid assembly of cellulose-anchored biofilms harbouring metabolically active yet antibiotic-tolerant bacilli, with minimal global transcriptional remodelling required for biofilm establishment.

Mycobacterial Biofilm Formation and Drug Tolerance publication trend

The graph below shows the total number of articles in mycobacterial biofilm formation and drug tolerance across all publications each year (not limited to Nature Index journals).

Technical terms

Biofilm: A structured community of bacterial cells embedded in an extracellular matrix that adheres to surfaces or interfaces.

Extracellular polymeric substance (EPS): The mixture of polysaccharides, proteins, lipids and nucleic acids that forms the biofilm matrix.

Phenotypic drug tolerance: A transient state in which bacteria survive antibiotic exposure without genetic resistance mechanisms.

Cyclic di-GMP: A bacterial second messenger that regulates biofilm formation and cell-wall lipid synthesis.

Nucleoid-associated protein Lsr2: A DNA-binding protein that senses cyclic di-GMP and controls expression of genes involved in lipid-mediated biofilm assembly.

Cellulose: A linear polysaccharide component of the biofilm matrix that contributes to structural integrity and antibiotic barrier function.

References

1. Lsr2 acts as a cyclic di-GMP receptor that promotes keto-mycolic acid synthesis and biofilm formation in mycobacteria. Nature Communications (2024).
2. Biofilm formation in the lung contributes to virulence and drug tolerance of Mycobacterium tuberculosis. Nature Communications (2021).
3. Thiol reductive stress induces cellulose-anchored biofilm formation in Mycobacterium tuberculosis. Nature Communications (2016).
4. In vitro and ex vivo proteomics of Mycobacterium marinum biofilms and the development of biofilm-binding synthetic nanobodies. mSystems (2023).
5. Synergistic antibacterial effects of ultrasound combined nanoparticles encapsulated with cellulase and levofloxacin on Bacillus Calmette-Guérin biofilms. Frontiers in Microbiology (2023).
6. Media component bovine serum albumin facilitates the formation of mycobacterial biofilms in response to reductive stress. BMC Microbiology (2023).