Abstract
Colicin M inhibits peptidoglycan biosynthesis at the level of the bactoprenyl carrier lipid. Since the synthesis of O-antigen also requires bactoprenyl carrier lipid, the effect of colicin M on O-antigen biosynthesis was studied using a colicin-sensitive strain of Salmonella typhimurium. Determination of O-antigen intermediates by two different methods showed that bactoprenyl-dependent O-antigen biosynthesis was inhibited by colicin M. Synthesis of both O-antigen and peptidoglycan was almost immediately inhibited following colicin addition. This was followed some 20 min later by cell lysis. The only known common step between O-antigen and peptidoglycan synthesis is formation of bactoprenyl phosphate by dephosphorylation of bactoprenyl pyrophosphate. Determination of bactoprenyl phosphates showed an accumulation of bactoprenyl pyrophosphate in colicin-treated cultures. It was concluded that dephosphorylation of the bactoprenyl lipid carrier was inhibited by colicin M, and this in turn prevented both O-antigen and peptidoglycan synthesis.
Highlights
RESULTS@-AntigenSynthesis-Cultures of strain RstlG(pHSC212) were incubated and treated with colicin M as described above under
Colicins recognize specific cell surface receptor proteins prior to being internalized by sensitive cells
Typhimur~umr,endered colicin “sensitive by the presence of Bacteriocins, toxins produced by bacteria which are active against related bacterial species, exert their lethal effects by a broad range of mechanisms (e.g.formation of ion-permeable pores in the target cell’s membrane, degradation of DNA or RNA, acting as phospholipases) (Konisky, 1982)
Summary
@-AntigenSynthesis-Cultures of strain RstlG(pHSC212) were incubated and treated with colicin M as described above under. The total amount of radioactive galact,ose incorporated by the cells was determined by adding an equal volume of cold 10%trichloroacetic acid to one of the duplicate samples. This sample was kept on ice for 30 min prior to filtration nitrocellulose filters, 0.45-pm pore size). RstlG(pHSC212) cultures to alkaline hydrolysis and trichloroacetic acid precipitation it was possible to quantitate 0polymer synthesisin the presence and absence of added colicin M. Fbdioactivity associated with peptidoglycan and lipid intermediate fractions in the pulse-labeled cell samples were separatbeydpaper chromatography and quantitated by determiningtheradioactivityintheindicatedfractionsasdescribed under "Exoerimental Procedures,"
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