Relationship among cell wall composition, stage of growth, and virulence of Nocardia asteroides GUH-2.
The clearance and organ distribution of virulent Nocardia asteroides GUH-2P and the avirulent mutant GUH-2AI at different stages of growth was determined after intravenous inoculation into BALB/c mice. The mutant differed significantly from the parent strain in its ability to survive and grow within the murine host. Since the mutant GUH-2AI had a very different colonial morphology compared with GUH-2P, it was believed that cell surface components might be affected by the mutation that resulted in the loss of virulence. Therefore, cell walls of both GUH-2P and GUH-2AI at different stages of growth were prepared and their composition determined. There were growth-stage-dependent changes in the composition of the cell walls that appeared to correlate with concurrent alterations in virulence; however, the overall chemical composition of the cell wall of the mutant (GUH-2AI) was not significantly different from that of the parent strain (GUH-2P). Both strains demonstrated significant modifications in fatty and mycolic acid composition at different stages of growth. Furthermore, the specific composition of C54 mycolic acids was very different in virulent log-phase cells compared with less-virulent stationary-phase cells, and the avirulent mutant lacked a C54:3 mycolate that was prominent in the virulent log-phase GUH-2P. Thus, C54:3 mycolic acid represented 2.5% of the cell wall (dry weight) in log-phase GUH-2P, but it was undetectable in the walls of GUH-2AI at the stationary phase of growth. These results suggest that certain mycolic acids are associated with virulence.
Beaman
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BL
Department of Medical Microbiology and Immunology, University of California School of Medicine, Davis 95616.
Moring
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SE
D000596:Amino Acids / Q000032:analysis; D000818:Animals; D002455:Cell Division; D002473:Cell Wall / Q000032:analysis / Q000502:physiology*; D051379:Mice; D009005:Monosaccharides / Q000032:analysis; D009171:Mycolic Acids / Q000032:analysis; D009615:Nocardia / Q000166:cytology / Q000472:pathogenicity* / Q000502:physiology; D009617:Nocardia Infections / Q000382:microbiology
D000596:Amino Acids; D009005:Monosaccharides; D009171:Mycolic Acids