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Comparative study of the events associated with colicin induction
Abstract:
Colicinogenic factors ColI and ColV, which have been shown to behave as sex factors, could not be induced with mitomycin C. In contrast, the ColE(1), ColE(2), and ColE(3) factors, which do not exhibit any fertility factor characteristics, are inducible by this agent. The induced production of colicins E(1), E(2), and E(3) was accompanied by a loss in viability at a concentration of mitomycin C which was bacteriostatic to noncolicinogenic cells or to cells carrying the ColV or ColI factors. The loss in viability accompanying the mitomycin C induction of the ColE(1), ColE(2), or ColE(3) factors also occurred when colicin synthesis was blocked by chloramphenicol or amino acid starvation. However, chloramphenicol was able to block the loss of viability of a recipient cell after mitomycin C induction of a newly acquired Col factor if the antibiotic was present throughout the mating period. No detectable internal colicin or colicin precursor could be demonstrated during the lag period prior to the appearance of colicin outside the cell 20 to 30 min after the addition of mitomycin C. If chloramphenicol was present during the lag period following the addition of mitomycin C, colicin synthesis began immediately after the removal of these antibiotics. The synthesis of tryptophan synthetase and induced beta-galactosidase proceeded normally throughout the lag period and well into the period of colicin production. Regulation of beta-galactosidase synthesis did not seem to be profoundly affected during the lag period subsequent to mitomycin C addition. Induced colicin synthesis, like bacterial or induced prophage protein synthesis, was subject to inhibition by virulent phage infection.
Insights
Mitomycin C induces colicin E production in certain bacteria, but not all. This induction leads to cell death, even when colicin synthesis is blocked.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- Colicinogenic factors (Col factors) are plasmids that confer colicin production.
- Some Col factors, like ColI and ColV, function as sex factors, while others, such as ColE1, ColE2, and ColE3, do not.
- Mitomycin C is known to induce prophages and certain plasmid-encoded functions.
Purpose of the Study:
- To investigate the inducibility of different colicinogenic factors by mitomycin C.
- To characterize the effects of mitomycin C induction on cell viability and colicin synthesis.
- To explore the regulatory mechanisms of colicin production.
Main Methods:
- Treatment of bacterial cells carrying different Col factors with mitomycin C.
- Assessment of colicin production and cell viability.
- Use of chloramphenicol and amino acid starvation to block colicin synthesis.
- Monitoring of other protein synthesis (tryptophan synthetase, beta-galactosidase) during induction.
- Evaluation of inhibition by virulent phage infection.
Main Results:
- ColE1, ColE2, and ColE3 factors were inducible by mitomycin C, unlike ColI and ColV.
- Mitomycin C induction of ColE factors resulted in a loss of cell viability, even at bacteriostatic concentrations.
- Cell death occurred independently of active colicin synthesis, persisting even when synthesis was blocked.
- A lag period of 20-30 minutes preceded detectable extracellular colicin.
- Synthesis of other proteins like tryptophan synthetase and beta-galactosidase was not significantly affected.
- Induced colicin synthesis was inhibited by virulent phage infection.
Conclusions:
- Colicinogenic factors lacking fertility characteristics are inducible by mitomycin C, leading to cell death.
- The mechanism of mitomycin C-induced cell death is linked to the induction process itself, not solely to colicin synthesis.
- Colicin production and regulation share some similarities with prophage induction and other protein synthesis pathways.