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Inhibition of lipopolysaccharide O-antigen synthesis by colicin M
1Mikrobiologie II, Universität Tübingen, Federal Republic of Germany.
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.
Insights
Colicin M blocks bacterial cell wall and O-antigen synthesis by inhibiting the bactoprenyl lipid carrier. This crucial inhibition of essential biosynthesis leads to bacterial cell lysis.
Area of Science:
- Microbiology
- Molecular Biology
- Biochemistry
Background:
- Colicin M is known to inhibit peptidoglycan biosynthesis.
- Peptidoglycan and O-antigen biosynthesis share the bactoprenyl carrier lipid.
- The precise mechanism of colicin M's action on O-antigen synthesis was unclear.
Purpose of the Study:
- To investigate the effect of colicin M on O-antigen biosynthesis.
- To elucidate the shared mechanism of inhibition between peptidoglycan and O-antigen synthesis by colicin M.
Main Methods:
- Utilized a colicin-sensitive strain of Salmonella typhimurium.
- Quantified O-antigen intermediates using two distinct analytical methods.
- Measured levels of bactoprenyl phosphates in treated bacterial cultures.
Main Results:
- Colicin M significantly inhibited bactoprenyl-dependent O-antigen biosynthesis.
- Both O-antigen and peptidoglycan synthesis were rapidly inhibited post-colicin M addition.
- Accumulation of bactoprenyl pyrophosphate was observed, indicating impaired dephosphorylation.
Conclusions:
- Colicin M inhibits the dephosphorylation of the bactoprenyl lipid carrier.
- This inhibition disrupts the supply of essential precursors for both O-antigen and peptidoglycan synthesis.
- The findings explain the broad inhibitory effect of colicin M on bacterial cell envelope construction.