The cell surface-exposed glycopeptidolipids confer a selective advantage to the smooth variants ofMycobacterium smegmatis in vitro

Abstract

The cell surface of mycobacteria is quite rich in lipids. Glycopeptidolipids, surface-exposed lipids that typify some mycobacterial species, have been associated with a phenotypic switch between rough and smooth colony morphotypes. This conversion in Mycobacterium smegmatis is correlated with the absence/presence of glycopeptidolipids on the cell surface and is due to insertion sequence mobility. Here, we show that the occurrence of a high amount of glycopeptidolipids in the smooth variant leads to lower invasion abilities and lower internalization by macrophages. We further show that the high production of glycopeptidolipids on the cell surface can confer a selective advantage to the smooth variant when grown in vitro. This higher fitness under the laboratory condition might explain the selection of smooth variants in several independent laboratories. The implications of these findings are discussed.

Identification and characterization of the genetic changes responsible for the characteristic smooth‐to‐rough morphotype alterations of clinically persistent Mycobacterium abscessus

“…After validating the integrity of the insert in the resulting construct, named pAP‐GPL, by comparative restriction profiling, PCR and sequence analyses, highly concentrated, dialized plasmid DNA preparations were transformed in parallel into M. abscessus 19977‐IP‐R and M. smegmatis mc 2 155 electrocompetent cells in repeated assays. It is noteworthy that the used M. smegmatis strain showed a rough colony type, apparently due to relatively low GPL synthesis (Kocincova et al ., ). Electroporation efficiency was drastically different between M. abscessus and M. smegmatis electrocompetent cells, i.e.…”

“…Attempts to isolate M. abscessus from natural environment or from water supply systems are often not successful (Bryant et al ., ), and might need particular decontamination procedures and the use of liquid media (Thomson et al ., 2013b; 2013a). As our data indicate that R morphotype mutants of M. abscessus have lost the ability to produce GPL due to small genetic changes interrupting the expression or translation of genes in the mps locus, we speculate that the presence of GPLs in the wild‐type variants of M. abscessus with characteristic S morphology, might help to establish infection (Kocincova et al ., ), whereas in a more long‐term host‐pathogen relation the loss of GPLs seems to favour chronic infection. So far, R forms of M. abscessus have mainly been cultivated from human samples or samples in direct contact with humans, but very rarely from any non‐patient related environmental sources (Kapoor and Yadav, ), similar to the situation observed for the mucoid forms of Pseudomonas aeruginosa that are exclusively found in conjunction with CF chronic lung infections (Deretic et al ., ).…”

The distinct fate of smooth and roughMycobacterium abscessusvariants inside macrophages

“…Mycobacterium smegmatis mc 2 155 strain, which derives originally from the ATCC 607 strain [69], expresses less triglycosylated GPL than M. abscessus or M . chelonae [67].…”

A Monoacylglycerol Lipase from Mycobacterium smegmatis Involved in Bacterial Cell Interaction

“…Previous authors have attributed this kind of change to an alteration in the lipid composition of the mycobacterium cell envelope having an impact on cell hydrophobicity (2,11,18,30,34). The conversion from a rough to a smooth appearance may be due to an overproduction of glycopeptidolipids on the cell surface (22) or a lack of trehalose dimycolate (30). Contrary to our expectations, the Ms⌬0220 cell envelope exhibited the same GPL, mycolic acid, and polar and apolar lipid contents as the M. smegmatis wild-type and ComMs⌬0220 cell envelopes.…”