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Colonial opacity variation in Mycoplasma pulmonis
Abstract:
Colonial size and opacity variation were observed in four independently isolated strains of the murine pathogen Mycoplasma pulmonis. Selecting colonial opacity variants of similar size, we identified opaque and transparent stable variants. Opaque colony-derived broth cultures shed transparent colonies at a rate of about 1.2 X 10(-8) per CFU per generation. The reverse conversion was about two orders of magnitude less frequent. Appearance of opacity and plating efficiency of each pure culture were altered by changing the serum source used to supplement the growth medium. Horse or sheep serum was most efficient at accentuating visualization of opacity differences. Fetal bovine serum was least efficient. In two M. pulmonis strains, each opacity variant showed a distinctive polypeptide profile, as displayed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. In the same strains, distinctive intrastrain differences were found by agarose gel electrophoresis to display the DNA fragments produced after digestion by several endonucleases. Each pure culture variant retained these differences in DNA even when grown in a medium supplemented with a serum which did not accentuate visualization of the opacity phenotype. Characterization of variants in 30 other M. pulmonis strains is in progress.
Insights
Mycoplasma pulmonis exhibits colonial opacity variation, with transparent variants arising from opaque cultures. Serum type influences opacity visualization and growth, while DNA and protein profiles distinguish variants.
Area of Science:
- Microbiology
- Bacteriology
- Pathogen Research
Background:
- Mycoplasma pulmonis is a significant murine pathogen.
- Colonial morphology, including opacity, can vary within bacterial populations.
Purpose of the Study:
- To investigate and characterize colonial opacity variants in Mycoplasma pulmonis.
- To determine the stability and interconversion rates of these variants.
- To explore factors influencing opacity expression and underlying molecular differences.
Main Methods:
- Isolation and selection of stable opaque and transparent colonial variants.
- Cultivation in media supplemented with different serum types (horse, sheep, fetal bovine).
- Analysis of protein profiles using SDS-PAGE.
- Analysis of DNA fragment patterns using agarose gel electrophoresis after endonuclease digestion.
Main Results:
- Stable opaque and transparent variants of Mycoplasma pulmonis were identified.
- Transparent variants arose from opaque cultures at a rate of 1.2 x 10(-8) per CFU per generation.
- Serum source significantly impacted opacity visualization and plating efficiency.
- Distinct polypeptide profiles and DNA fragment patterns differentiated variants within specific strains.
- These molecular differences were stable across different serum supplements.
Conclusions:
- Colonial opacity in Mycoplasma pulmonis is a heritable trait with distinct molecular underpinnings.
- Environmental factors, such as serum composition, modulate phenotype expression.
- Opaque and transparent variants possess stable genetic and proteomic differences.