Ultralong C100 mycolic acids support the assignment of Segniliparus as a new bacterial genus.
Mycolic acid-producing bacteria isolated from the respiratory tract of human and non-human mammals were recently assigned as a distinct genus, Segniliparus, because they diverge from rhodococci and mycobacteria in genetic and chemical features. Using high accuracy mass spectrometry, we determined the chemical composition of 65 homologous mycolic acids in two Segniliparus species and separately analyzed the three subclasses to measure relative chain length, number and stereochemistry of unsaturations and cyclopropyl groups within each class. Whereas mycobacterial mycolate subclasses are distinguished from one another by R groups on the meromycolate chain, Segniliparus species synthesize solely non-oxygenated α-mycolates with high levels of cis unsaturation. Unexpectedly Segniliparus α-mycolates diverge into three subclasses based on large differences in carbon chain length with one bacterial culture producing mycolates that range from C58 to C100. Both the overall chain length (C100) and the chain length diversity (C42) are larger than previously seen for mycolic acid-producing organisms and provide direct chemical evidence for assignment of Segniliparus as a distinct genus. Yet, electron microscopy shows that the long and diverse mycolates pack into a typical appearing membrane. Therefore, these new and unexpected extremes of mycolic acid chemical structure raise questions about the modes of mycolic acid packing and folding into a membrane.
Division of Rheumatology, Immunology and Allergy, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, United States of America.
Sunhee
S
Hong
Tan-Yun
TY
Cheng
Emilie
E
Layre
Lindsay
L
Sweet
David C
DC
Young
James E
JE
Posey
W Ray
WR
Butler
D Branch
DB
Moody
D000192:Actinomycetales / Q000145:classification / Q000378:metabolism*; D002853:Chromatography, Liquid; D002855:Chromatography, Thin Layer; D013058:Mass Spectrometry; D008745:Methylation; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D009171:Mycolic Acids / Q000378:metabolism*; D019906:Nuclear Magnetic Resonance, Biomolecular; D021241:Spectrometry, Mass, Electrospray Ionization
D009171:Mycolic Acids