A Thermosensitive Mutant of Escherichia Coli With a Defect in the Process of Cell Division

Abstract

A thermosensitive mutant of Escherichia coli (E. coli strain ts612) was isolated by the transduction of polA+ as a selective marker with phage Plc which had been mutagenized with hydroxylamine. The mutation was mapped between ilv (74.7 min) and metE (75.5 min). When the incubation temperature of this mutant was shifted from 30° to 42°, the cell division was interrupted immediately after the shift of temperature, although the optical density at 660 nm of the culture continued to increase for 90 min. The mutant did not support the multiplications of phages T4 and lambda at 42°, while it allowed the growth of phage T7. Electrophoretic analysis of membrane proteins of the mutant suggested that a part of the membrane protein was diminished when the mutant was incubated at the restrictive temperature.Specialized mutations in Escherichia coli can be induced by means of transduction with mutagenized phage P1. When an appropriate genetic marker was transduced with mutagenized phage particles, the transductants would involve a mutant which had a mutation closely linked to the selected marker. By this means it is possible to induce mutation in the specific region of the chromosome. Several mutants of Salmonella typhimurium were isolated by a similar method using a mutagenized phage P22 (1).With the intention of obtaining a new class of mutants having defects (2, 3) in the machinery of DNA synthesis, transduction of E. coli polA was made with the mutagenized phage Plc. Several thermosensitive mutants were isolated among the polA+ transductants and were characterized. Since one of these thermosensitive mutants seemed to have various interesting properties concerning the cell division and phage growth, the characterization of the mutant was performed which is described in this report.

Correlation of Biosynthesis and Shape-Determining Properties of the Peptidoglycan and Cell Division in Temperature-Sensitive Mutants of Escherichia Coli

“…Relationship between PG synthesis and cell division When E. coli mutants, TS for cell division, are placed at their non-permissive growth temperature, cell division will stop, either immediately or after some time (18)(19)(20)(21)(22)(23). The basis for a particular cell division pattern has often been attributed to the role of the TS phenotype(s) and the function that they affect in the cell division sequence.…”

“…Several of these mutants appear to accumulate division potential and upon recovery they divide at a fast rate. This feature appears in many other cell division mutants of E. coli (18)(19)(20)(21)(22)(23)27) and is due to cell division of a filamentous bacterial cell into many smaller sized single cells. Such cell division mutants showed an ability to undergo recovery in the presence of CAM.…”