Abstract
Mycobacterium smegmatis has been widely used as a mycobacterial infection model. Unlike the M. smegmatis mc2155 strain, M. smegmatis J15cs strain has the advantage of surviving for one week in murine macrophages. In our previous report, we clarified that the J15cs strain has deleted apolar glycopeptidolipids (GPLs) in the cell wall, which may affect its morphology and survival in host cells. In this study, the gene causing the GPL deletion in the J15cs strain was identified. The mps1-2 gene (MSMEG_0400-0402) correlated with GPL biosynthesis. The J15cs strain had 18 bps deleted in the mps1 gene compared to that of the mc2155 strain. The mps1-complemented J15cs mutant restored the expression of GPLs. Although the J15cs strain produces a rough and dry colony, the colony morphology of this mps1-complement was smooth like the mc2155 strain. The length in the mps1-complemented J15cs mutant was shortened by the expression of GPLs. In addition, the GPL-restored J15cs mutant did not survive as long as the parent J15cs strain in the murine macrophage cell line J774.1 cells. The results are direct evidence that the deletion of GPLs in the J15cs strain affects bacterial size, morphology, and survival in host cells.
Highlights
Tuberculosis is an infectious disease worldwide, and the causative agent, Mycobacterium tuberculosis, is a slow-growing intracellular pathogen
It is necessary to clarify the mechanisms of host–pathogen interactions and how the pathogen survives in host cells
We previously reported that the J15cs strain replicated our original vector, pYT923, and survived in host cells longer than the mc2155 strain [1]
Summary
Tuberculosis is an infectious disease worldwide, and the causative agent, Mycobacterium tuberculosis, is a slow-growing intracellular pathogen. It is necessary to clarify the mechanisms of host–pathogen interactions and how the pathogen survives in host cells. The M. smegmatis mc2155 strain is widely used because of its high rate of transformation. We screened another M. smegmatis strain, J15cs, and constructed a convenient and safe host-vector system of a mycobacterial model. The J15cs strain lacks glycopeptidolipids (GPLs) on the cell surface, and this may affect its morphology and survival in host cells [2]. GPL, called C-mycoside, is produced in the outer layer of some non-tuberculous mycobacteria, including Mycobacterium avium, M. intracellulare, M. scrofulaceum, M. abscessus, M. chelonae, and M. smegmatis. Recovery of the GPLs affected colony morphology and survival in host cells
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