Isolation, characterization, and action of colicin M

Area of Science:

• Microbiology
• Molecular Biology
• Biochemistry

Background:

• Colicins are bacteriocins produced by bacteria.
• Colicin M is known to be toxic to susceptible bacteria.

Purpose of the Study:

• To characterize Colicin M and elucidate its mechanism of action on Escherichia coli.
• To investigate the role of sucrose in protecting bacterial cells from Colicin M.

Main Methods:

• Isolation and purification of Colicin M.
• Polyacrylamide gel electrophoresis (PAGE) with sodium dodecyl sulfate (SDS) for molecular weight determination.
• Phase contrast and electron microscopy to observe cell lysis and spheroplast formation.
• Viability assays and protein release measurements.

Main Results:

• Purified Colicin M has a molecular weight of 27,000 and contains phosphatidyl ethanolamine.
• The polypeptide chain molecular weight is 18,000.
• Colicin M integrates into the producing cell membrane and causes rapid lysis of susceptible E. coli.
• Lysis involves cell envelope bulging, cytoplasmic membrane retraction, and protein release.
• Sucrose protects cells from lysis, especially when cells are pre-grown in its presence.

Conclusions:

• Colicin M acts on the bacterial cell membrane, leading to cell death.
• Sucrose pre-treatment enhances bacterial resistance to Colicin M-induced lysis.