Abstract
Lipooligosaccharides are glycolipids found in the cell wall of many mycobacterial species including the opportunistic pathogen Mycobacterium kansasii. The genome of M. kansasii ATCC12478 contains a cluster with genes orthologous to Mycobacterium marinum LOS biosynthesis genes. To initiate a genetic dissection of this cluster and demonstrate its role in LOS biosynthesis in M. kansasii, we chose MKAN27435, a gene encoding a putative glycosyltransferase. Using Specialized Transduction, a phage-based gene knockout tool previously used to generate null mutants in other mycobacteria, we generated a MKAN27435 null mutant. The mutant strain was found to be defective in the biosynthesis of higher LOS subspecies, viz LOS-IV, LOS-V, LOS-VI and LOS-VII. Additionally, a range of low abundance species were detected in the mutant strain and mass spectroscopic analysis indicated that these were shunt products generated from LOS-III by the addition of up to six molecules of a pentose.
Highlights
Unique lipids found in the distinct cell wall of mycobacteria are important for integrity and some play a vital role in virulence [1,2]
By comparing the LOS biosynthesis gene cluster from M. marinum with the M. kansasii ATCC12478 genome sequence, we identified a potential LOS biosynthesis cluster in M. kansasii containing ORFs encoding putative proteins with domains found in glycosyl transferases (GTFs)
Compared to five LOS-associated glycosyl transferase (GTF) genes found in M. marinum, the M. kansasii LOS biosynthetic cluster contains eight genes encoding putative GTFs
Summary
Unique lipids found in the distinct cell wall of mycobacteria are important for integrity and some play a vital role in virulence [1,2]. Lipooligosaccharides (LOS’s) are cell wall associated glycolipids produced by many mycobacterial species including Mycobacterium canetti, the ‘smooth’ Mycobacterium tuberculosis complex (MTBC) strain [3]. Mycobacterium tuberculosis, a MTBC strain, does not produce LOSs but the genome of M. tuberculosis H37Rv does contain a ‘reduced’ LOS biosynthetic cluster representative of approximately a third of genes found in M. canetti [4]. Other LOS producers include the opportunistic pathogen Mycobacterium kansasii and poikilotherm pathogen Mycobacterium marinum [5,6]. M. kansasii causes chronic pulmonary and disseminated infections in humans and is the second most common cause of non-tuberculosis mycobacterial (NTM) infections after Mycobacterium avium complex (MAC) [7,8,9]. There are subtle differences in lung lesions caused by PLOS ONE | DOI:10.1371/journal.pone.0122804 April 20, 2015
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