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Strain-specific variation in the protein and lipopolysaccharide composition of the group B meningococcal outer
Abstract:
Variation in the protein and lipopolysaccharide composition of the meningococcal outer membrane may be due to either serotype differences or to changes in cultural conditions. There are 12 antigenically distinct serotypes of group B meningococci, and these are associated with distinct major outer membrane protein patterns on sodium dodecyl sulfate-polyacrylamide gels. In most strains the predominant outer membrane protein carries the serotype-specific determinant. Certain strains, when grown under similar conditions in different media showed an altered membrane composition. The type 2 strain, M986, grown in modified Frantz medium-A, had a reduced amount of the major 41,000-dalton protein while a 28,000-dalton protein predominated. The altered protein composition may be related to changes in cell metabolism as reflected by the pH of the medium after growth. Growth of the organism in Frantz medium-B caused a negligible drop in pH and the 41,000-dalton protein remained predominant. There was also variation associated with changes in the growth rate. Increasing the aeration caused a concomitant increase in growth rate and cell yield. We observed two quantitative changes in outer membrane proteins in four of seven strains examined: (i) where only a single major protein changed (three strains), and (ii) where an increase in one protein component was associated with a decrease in another protein (one strain). When the strains were grown in tryptic soy broth (Difco Laboratories, Detroit, Mich.) with either high or low aeration, the total protein in the outer membrane remained constant. In contrast, with high aeration there was a significant increase in lipopolysaccharide. These studies suggest that the cell surface proteins may be altered by the organism to meet a variety of environmental conditions.
Insights
Environmental conditions significantly alter the outer membrane composition of meningococci (Neisseria meningitidis). Changes in growth media and aeration affect protein and lipopolysaccharide levels, influencing bacterial adaptation.
Area of Science:
- Microbiology
- Bacterial Pathogenesis
- Molecular Biology
Background:
- Neisseria meningitidis (meningococcus) outer membrane composition varies, influenced by serotype and growth conditions.
- Twelve distinct serotypes of group B meningococci exist, each with unique outer membrane protein patterns.
- The predominant outer membrane protein often carries serotype-specific determinants.
Purpose of the Study:
- To investigate how environmental factors, specifically cultural conditions, impact meningococcal outer membrane protein and lipopolysaccharide composition.
- To determine the relationship between altered membrane composition, cell metabolism, growth rate, and environmental cues.
Main Methods:
- Analysis of outer membrane protein and lipopolysaccharide profiles using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE).
- Cultivation of meningococcal strains (including type 2 strain M986) in various media (modified Frantz medium-A, Frantz medium-B, tryptic soy broth) under different aeration levels.
- Monitoring of growth rate, cell yield, and medium pH changes.
Main Results:
- Altered growth media significantly changed outer membrane composition; modified Frantz medium-A reduced a 41,000-dalton protein and increased a 28,000-dalton protein in strain M986.
- Growth conditions affecting pH influenced protein profiles, with negligible pH drop in Frantz medium-B maintaining the 41,000-dalton protein.
- Increased aeration enhanced growth rate and cell yield, leading to quantitative changes in outer membrane proteins in some strains and increased lipopolysaccharide in tryptic soy broth.
Conclusions:
- Meningococcal outer membrane protein and lipopolysaccharide composition are plastic and responsive to environmental changes.
- Cell metabolism and growth rate are linked to alterations in outer membrane structure.
- These adaptive changes in cell surface proteins suggest a mechanism for the organism to respond to diverse environmental conditions.