Alternative forms of lethality in mitomycin C-induced bacteria carrying ColE1 plasmids

Area of Science:

• Molecular Biology
• Cell Biology
• Genetics

Background:

• Colicin E1 plasmids encode colicin, immunity, and a mitomycin C-inducible lethality (kil) gene.
• The kil gene's location relative to colicin (cea) and immunity (imm) genes influences cellular response to mitomycin C.

Purpose of the Study:

• To investigate the physiological effects of mitomycin C induction on cells harboring ColE1 plasmids with varying gene configurations.
• To differentiate the roles of the kil gene and endogenous colicin in mitomycin C-induced cell death and damage.

Main Methods:

• Utilized ColE1 plasmids with modified cea, kil, and imm gene arrangements.
• Induced cells with mitomycin C and monitored physiological changes including cell viability, macromolecular synthesis, nutrient transport, and membrane permeability.
• Assessed damage in cells with varying plasmid constructs, including those lacking kil or imm functions.

Main Results:

• Mitomycin C induction of plasmids with cea(+)kil(+) or cea(-)kil(+)imm(+) resulted in >90% cell death, cessation of synthesis, loss of transport, and altered membrane permeability.
• Damage was attributed to the kil function, not colicin presence, as cea(+)kil(-)imm(+) cells showed different damage patterns.
• Cells with cea(+)kil(-)imm(-) plasmids were killed by endogenous colicin, exhibiting enhanced alpha-methyl glucoside uptake and efflux, distinct from kil-induced damage.

Conclusions:

• The kil gene is the primary determinant of mitomycin C-induced lethality and associated physiological damage in ColE1 plasmid-carrying cells.
• Endogenous colicin can also induce cell death in non-immune cells, but with distinct physiological consequences compared to kil-mediated death.
• Cellular damage originates internally, independent of external factors like trypsin or tolerance to exogenous colicin.