Biofilms of the non-tuberculous form an extracellular matrix and display distinct expression patterns.

is an environmental, non-tuberculous mycobacterial species, capable of causing infections in humans. Biofilm formation is a key strategy used by in colonising niches in the environment and in the host. We studied a water-air interface (pellicle) biofilm of using a wide array of approaches to outline the molecular structure and composition of the biofilm. Scanning electron micrographs showed that biofilms produced an extracellular matrix. Using a combination of biochemical analysis, Raman spectroscopy, and fluorescence microscopy, we showed the matrix to consist of proteins, carbohydrates, lipids and eDNA. Glucose was the predominant sugar present in the biofilm matrix, and its relative abundance decreased in late (established) biofilms. RNA-seq analysis of the biofilms showed upregulation of genes involved in redox metabolism. Additionally, genes involved in mycolic acid, other lipid and glyoxylate metabolism were also upregulated in the early biofilms.