Characterization of biofilm formation by clinical isolates of Mycobacterium avium

Carter, George; Wu, Martin; Drummond, Daryl C.; Bermudez, Luiz E.

doi:10.1099/jmm.0.05224-0

Cited by 153 publications

(156 citation statements)

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“…Although the in vivo formation of biofilms by M. tuberculosis remains a matter of debate (21), it is well established that Mycobacterium smegmatis and other environmental mycobacteria such as M. avium subsp. avium, M. fortuitum, M. chelonae, and M. marinum are capable of biofilm formation (7,14,40). These mycobacteria are normal inhabitants of a wide variety of environmental reservoirs, including natural and municipal waters.…”

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Roles of Lsr2 in Colony Morphology and Biofilm Formation ofMycobacterium smegmatis

et al. 2006

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The lipid-rich cell wall is a defining feature of Mycobacterium species. Individual cell wall components affect diverse mycobacterial phenotypes including colony morphology, biofilm formation, antibiotic resistance, and virulence. In this study, we describe a transposon insertion mutant of Mycobacterium smegmatis mc 2 155 that exhibits altered colony morphology and defects in biofilm formation. The mutation was localized to the lsr2 gene. First identified as an immunodominant T-cell antigen of Mycobacterium leprae, lsr2 orthologs have been identified in all sequenced mycobacterial genomes, and homologs are found in many actinomycetes. Although its precise function remains unknown, localization experiments indicate that Lsr2 is a cytosolic protein, and cross-linking experiments demonstrate that it exists as a dimer. Characterization of cell wall lipid components reveals that the M. smegmatis lsr2 mutant lacks two previously unidentified apolar lipids. Characterization by mass spectrometry and thin-layer chromatography indicate that these two apolar lipids are novel mycolatecontaining compounds, called mycolyl-diacylglycerols (MDAGs), in which a mycolic acid (␣-or ␣-mycolate) molecule is esterified to a glycerol. Upon complementation with an intact lsr2 gene, the mutant reverts to the parental phenotypes and MDAG production is restored. This study demonstrates that due to its impact on the biosynthesis of the hydrophobic MDAGs, Lsr2 plays an important role in the colony morphology and biofilm formation of M. smegmatis.The cell wall is a defining feature of mycobacteria. This complex, lipid-rich, hydrophobic structure is responsible for the acid-fast staining properties, distinctive colony morphology, and innate antibiotic resistance of Mycobacterium species (12,25,28). Among pathogens, including Mycobacterium tuberculosis, the causative agent of tuberculosis, cell wall components contribute to virulence, persistence within macrophages, and modulation of the host immune response (16, 45).The cell wall forms an asymmetric lipid bilayer (25,28). The inner leaflet is composed of mycolic acids that are covalently bound to arabinogalactan, which is further linked to peptidoglycan via a phosphodiester bridge (12). The outer leaflet contains a variety of lipid components (26,28). In total, lipids comprise 60% (wt/wt) of the cell wall (12, 25). In addition to mycolic acids, various types of complex lipids are present in the cell wall. These include lipoglycans (e.g., lipoarabinomannan [LAM]), trehalose-containing glycolipids, phthiocerol dimycocerosates, phenolic glycolipids, and glycopeptidolipids (GPLs) (12, 25). The distribution of these lipids varies among mycobacterial species (12). Triacylglycerols (TAGs) are also present in the mycobacterial cell wall (35) and are thought to fill the gap between the meromycolate arm and the shorter ␣-chain of mycolic acids (28). Different lipids appear to have different roles. For example, LAM from M. tuberculosis, but not the structurally distinct LAM of nonpathogenic mycobacteria,...

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Roles of Lsr2 in Colony Morphology and Biofilm Formation ofMycobacterium smegmatis

et al. 2006

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“…Mycobacterium smegmatis, as well as M. avium, has been shown to produce a biofilm or a biofilm-like structure (6,19). The outermost layers of the M. smegmatis and M. avium cell walls contain glycopeptidolipid (GPL), whereas the outermost layer of M. tuberculosis is made of phenolic glycolipids, dimycocerosate, and lipo-oligosaccharides (24).…”

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Mycobacterium aviumGenes Associated with the Ability To Form a Biofilm

Yamazaki¹,

Danelishvili²,

Wu³

et al. 2006

Appl Environ Microbiol

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114

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Mycobacterium avium is widely distributed in the environment, and it is chiefly found in water and soil. M. avium, as well as Mycobacterium smegmatis, has been recognized to produce a biofilm or biofilm-like structure. We screened an M. avium green fluorescent protein (GFP) promoter library in M. smegmatis for genes involved in biofilm formation on polyvinyl chloride (PVC) plates. Clones associated with increased GFP expression >2.0-fold over the baseline were sequenced. Seventeen genes, most encoding proteins of the tricarboxylic acid (TCA) cycle and GDP-mannose and fatty acid biosynthesis, were identified. Their regulation in M. avium was confirmed by examining the expression of a set of genes by real-time PCR after incubation on PVC plates. In addition, screening of 2,000 clones of a transposon mutant bank constructed using M. avium strain A5, a mycobacterial strain with the ability to produce large amounts of biofilm, revealed four mutants with an impaired ability to form biofilm. Genes interrupted by transposons were homologues of M. tuberculosis 6-oxodehydrogenase (sucA), enzymes of the TCA cycle, protein synthetase (pstB), enzymes of glycopeptidolipid (GPL) synthesis, and Rv1565c (a hypothetical membrane protein). In conclusion, it appears that GPL biosynthesis, including the GDP-mannose biosynthesis pathway, is the most important pathway involved in the production of M. avium biofilm.Mycobacterium avium complex is widely distributed in the environment, such as in water and soil, and is a chief component of many natural aquatic biofilms (8). M. avium is also known to cause chronic pulmonary infection in patients with predisposing lung disease, such as previous tuberculosis and chronic obstructive pulmonary disease (28). Urban water systems contain organisms of the M. avium complex in biofilm or a biofilm-like structure, and individuals can potentially be exposed to the bacterium, either by inhalation of aerosol particles or ingestion of contaminated water. Studies have established an association between M. avium in urban water and the development of disseminated disease in individuals with AIDS (36).Mycobacterium smegmatis, as well as M. avium, has been shown to produce a biofilm or a biofilm-like structure (6, 19). The outermost layers of the M. smegmatis and M. avium cell walls contain glycopeptidolipid (GPL), whereas the outermost layer of M. tuberculosis is made of phenolic glycolipids, dimycocerosate, and lipo-oligosaccharides (24). Recent studies suggest that the M. smegmatis biofilm is associated with a GPL present on the cell wall, and indirect evidence indicates a similar role in M. avium (6). Aspects of biofilm formation have begun to be examined with M. smegmatis. Transposon inactivation of the GPL gene clusters in M. smegmatis decreased the production of biofilm, and the deletion of the genes tmtp and mps revealed their involvement in biofilm formation upon seeding of the bacterium on polyvinyl chloride (PVC) plates (19,26). The tmtp gene is highly conserved between M. smegmatis and M. avium, ...

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“…Interestingly, such growth pattern of mycobacteria have frequently been noted in the literature as aggregation of cells driven by their surface hydrophobicity, and largely been ignored ever since Dubos and colleagues reported a method to grow dispersed culture of tubercle bacilli without diminishing their virulence (Dubos et al, 1946). However, the emerging concept of microbial persistence in biofilms have recently led several groups to investigate the detergent-free in vitro growth of mycobacterial species from the perspective of organized multicellular structures (Hall-Stoodley & Lappin-Scott, 1998, Carter et al, 2003. In one of the first genetic studies of surface associated growth of mycobacteria, Kolter and colleagues observed that an M. smemgatis mutant deficient in biosynthesis of acetylated glycopeptidolipid was also unable to attach and grow on an abiotic surface, thus demonstrating a specific genetic requirement for surface-associate mycobacterial growth (Recht & Kolter, 2001).…”

Section: Could M Tuberculosis Infections Persist As Biofilms?mentioning

confidence: 99%