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Ultralong C100 mycolic acids support the assignment of Segniliparus as a new bacterial genus.

Hong S, Cheng TY, Layre E, Sweet L, Young DC, Posey JE, Butler WR, Moody DB - PLoS ONE (2012)

Bottom Line: 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.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.

View Article: PubMed Central - PubMed

Affiliation: Division of Rheumatology, Immunology and Allergy, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, United States of America.

ABSTRACT
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.

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Electron micrographs.Scanning electron micrographs of S. rotundus (A) and S. rugosus (B). (C) Transmission electron micrograph of S. rugosus. The bands are labeled as indicated. MOM stands for mycolate outer membrane and CM stands for cytoplasmic membrane.
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pone-0039017-g001: Electron micrographs.Scanning electron micrographs of S. rotundus (A) and S. rugosus (B). (C) Transmission electron micrograph of S. rugosus. The bands are labeled as indicated. MOM stands for mycolate outer membrane and CM stands for cytoplasmic membrane.

Mentions: S. rotundus and S. rugosus show differing smooth and rough colony forms, and display somewhat distinct appearance by electron microscopy (Fig. 1) [10]. Transmission electron microscopy (TEM) identified two layers showing the characteristic appearance of formed lipid membranes: triple bands composed of alternating electron dense and light regions. The ultrathin TEM images for Segniliparus rugosus are interpreted as an electron transparent periplasmic space, enclosed by a triple-layer of alternating dense and transparent bands typical of a mycolate membrane and surrounded by a less electron dense outermost capsule layer. The capsular layer was irregularly shaped and was present in S. rugosus but not in S. rotundus. The multilayered appearance of the Segniliparus envelope recapitulated most known aspects of mycobacterial structures.


Ultralong C100 mycolic acids support the assignment of Segniliparus as a new bacterial genus.

Hong S, Cheng TY, Layre E, Sweet L, Young DC, Posey JE, Butler WR, Moody DB - PLoS ONE (2012)

Electron micrographs.Scanning electron micrographs of S. rotundus (A) and S. rugosus (B). (C) Transmission electron micrograph of S. rugosus. The bands are labeled as indicated. MOM stands for mycolate outer membrane and CM stands for cytoplasmic membrane.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3375245&req=5

pone-0039017-g001: Electron micrographs.Scanning electron micrographs of S. rotundus (A) and S. rugosus (B). (C) Transmission electron micrograph of S. rugosus. The bands are labeled as indicated. MOM stands for mycolate outer membrane and CM stands for cytoplasmic membrane.
Mentions: S. rotundus and S. rugosus show differing smooth and rough colony forms, and display somewhat distinct appearance by electron microscopy (Fig. 1) [10]. Transmission electron microscopy (TEM) identified two layers showing the characteristic appearance of formed lipid membranes: triple bands composed of alternating electron dense and light regions. The ultrathin TEM images for Segniliparus rugosus are interpreted as an electron transparent periplasmic space, enclosed by a triple-layer of alternating dense and transparent bands typical of a mycolate membrane and surrounded by a less electron dense outermost capsule layer. The capsular layer was irregularly shaped and was present in S. rugosus but not in S. rotundus. The multilayered appearance of the Segniliparus envelope recapitulated most known aspects of mycobacterial structures.

Bottom Line: 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.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.

View Article: PubMed Central - PubMed

Affiliation: Division of Rheumatology, Immunology and Allergy, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, United States of America.

ABSTRACT
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.

Show MeSH
Related in: MedlinePlus