3 years ago

Defining a temporal order of genetic requirements for development of mycobacterial biofilms

Defining a temporal order of genetic requirements for development of mycobacterial biofilms
Catherine Vilchèze, Joseph Thomas, Keith M. Derbyshire, Anil K. Ojha, William R. Jacobs, Yunlong Li, Yong Yang
Most mycobacterial species spontaneously form biofilms, inducing unique growth physiologies and reducing drug sensitivity. Biofilm growth progresses through three genetically programmed stages: substratum attachment, intercellular aggregation and architecture maturation. Growth of Mycobacterium smegmatis biofilms requires multiple factors including a chaperonin (GroEL1) and a nucleoid-associated protein (Lsr2), although how their activities are linked remains unclear. Here it is shown that Lsr2 participates in intercellular aggregation, but substratum attachment of Lsr2 mutants is unaffected, thereby genetically distinguishing these developmental stages. Further, a suppressor mutation in a glycopeptidolipid synthesis gene (mps) that results in hyperaggregation of cells and fully restores the form and functions of Δlsr2 mutant biofilms was identified. Suppression by the mps mutation is specific to Δlsr2; it does not rescue the maturation-deficient biofilms of a ΔgroEL1 mutant, thereby differentiating the process of aggregation from maturation. Gene expression analysis supports a stepwise process of maturation, highlighted by temporally separated, transient inductions of iron and nitrogen import genes. Furthermore, GroEL1 activity is required for induction of nitrogen, but not iron, import genes. Together, the findings begin to define molecular checkpoints during development of mycobacterial biofilms. This study exploits a fortuitously discovered suppressor of a biofilm-defective mutant, lsr2, to map the temporal order of genetic activities during biofilm development in mycobacteria. Genes involved in substratum attachment, intercellular aggregation and maturation are distinguished. Comparison of transcriptomes of lsr2 mutant with its suppressor redefines the role of Lsr2 and glycopeptidolipids in biofilm development, and also identifies genes, which are induced upon intercellular aggregation and play important role in maturation.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1111/mmi.13734

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