Identification of a stress-induced factor of Corynebacterineae that is involved in the regulation of the outer membrane lipid composition.
Corynebacterineae are gram-positive bacteria that possess a true outer membrane composed of mycolic acids and other lipids. Little is known concerning the modulation of mycolic acid composition and content in response to changes in the bacterial environment, especially temperature variations. To address this question, we investigated the function of the Rv3802c gene, a gene conserved in Corynebacterineae and located within a gene cluster involved in mycolic acid biosynthesis. We showed that the Rv3802 ortholog is essential in Mycobacterium smegmatis, while its Corynebacterium glutamicum ortholog, NCgl2775, is not. We provided evidence that the NCgl2775 gene is transcriptionally induced under heat stress conditions, and while the corresponding protein has no detectable activity under normal growth conditions, the increase in its expression triggers an increase in mycolic acid biosynthesis concomitant with a decrease in phospholipid content. We demonstrated that these lipid modifications are part of a larger outer membrane remodeling that occurs in response to exposure to a moderately elevated temperature (42 degrees C). In addition to showing an increase in the ratio of saturated corynomycolates to unsaturated corynomycolates, our results strongly suggested that the balance between mycolic acids and phospholipids is modified inside the outer membrane following a heat challenge. Furthermore, we showed that these lipid modifications help the bacteria to protect against heat damage. The NCgl2775 protein and its orthologs thus appear to be a protein family that plays a role in the regulation of the outer membrane lipid composition of Corynebacterineae under stress conditions. We therefore propose to name this protein family the envelope lipids regulation factor (ElrF) family.
Centre National de la Recherche Scientifique (CNRS), Institut de Pharmacologie et de Biologie Structurale (IPBS), Département Mécanismes Moléculaires des Infections Mycobactériennes, Toulouse, France.
Xavier
X
Meniche
Cécile
C
Labarre
Célia
C
de Sousa-d'Auria
Emilie
E
Huc
Françoise
F
Laval
Marielle
M
Tropis
Nicolas
N
Bayan
Damien
D
Portevin
Christophe
C
Guilhot
Mamadou
M
Daffé
Christine
C
Houssin
D001426:Bacterial Proteins / Q000235:genetics / Q000502:physiology*; D048230:Corynebacterium glutamicum / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial / Q000235:genetics / Q000502:physiology; D050356:Lipid Metabolism / Q000235:genetics / Q000502:physiology*; D008563:Membrane Lipids / Q000235:genetics / Q000378:metabolism*; D020102:Mycobacterium smegmatis / Q000235:genetics / Q000378:metabolism; D009169:Mycobacterium tuberculosis / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013696:Temperature
D001426:Bacterial Proteins; D008563:Membrane Lipids