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Cell wall lipopolysaccharide response to the ColIb plasmid mutants
Acta Microbiologica Polonica
|January 1, 1976
Summary
Colicin plasmids alter Salmonella lipopolysaccharide (LPS) O-side chain synthesis. Mutants reduced key sugars and repeating units, demonstrating plasmid control over LPS structure.
Area of Science:
- Microbiology
- Molecular Biology
- Biochemistry
Background:
- Lipopolysaccharides (LPS) are crucial outer membrane components of Gram-negative bacteria, influencing virulence and host interactions.
- Salmonella LPS O-side chains are highly variable and composed of repeating oligosaccharide units.
- Colicin plasmids are known to affect bacterial physiology, but their role in LPS modification is less understood.
Purpose of the Study:
- To investigate the impact of Colicin Ib (ColIb) plasmid mutants on the O-side chain synthesis of Salmonella lipopolysaccharides (LPS).
- To identify specific genetic elements on the plasmid responsible for altering LPS composition and structure.
- To understand the regulatory mechanisms by which plasmids influence bacterial surface antigen expression.
Main Methods:
- Bacterial culture and manipulation of Salmonella strains (S. typhimurium, S. enteritidis, S. meleagridis).
- Introduction of specific ColIb plasmid mutants (srd 25, drd2) into Salmonella.
- Biochemical analysis of LPS composition, including sugar content (rhamnose, mannose, abequose, tyvelose) and repeating unit number.
Main Results:
- The srd 25 plasmid mutant significantly reduced rhamnose and mannose content and eliminated abequose in S. typhimurium LPS.
- Introduction of srd 25 decreased the number of repeating units in the O-side chains.
- The drd2 plasmid mutant led to dideoxyhexose-defective O-side chains lacking abequose (S. typhimurium, S. enteritidis) or tyvelose (S. enteritidis).
- In S. meleagridis, dideoxyhexose-deficient mutants showed reduced rhamnose and mannose content.
- Plasmid genomes contained the information for these LPS alterations, with genes in wild-type plasmids being unexpressed.
Conclusions:
- ColIb plasmid mutants directly influence the synthesis and composition of Salmonella LPS O-side chains.
- Specific plasmid genes control the incorporation of sugars and the length of O-side chains.
- Unexpressed genes in wild-type plasmids suggest a regulatory mechanism controlling LPS modification in response to plasmid presence.