Lack of UV-induced respiration shutoff in a recF strain of Escherichia coli: temperature conditional suppression at 30 degrees C by the sfrA mutation.

A mutation in the recF gene of Escherichia coli results in a radiation-sensitive strain. The RecF pathway and the RecBC pathway account for nearly all of the conjugative recombination occurring in E. coli. recBC cells are radiation-sensitive and carry only out a small amount of recombination but these deficiencies are suppressed by an sbcB as recombination is shunted to the RecF pathway. A recBC sbcB recF strain is very radiation-sensitive and is devoid of recombination ability. These deficiencies are suppressed by the srfA mutation; srfA is a recA allele. UV-induced respiration shutoff is a recA+, lexA+ and recBC+ dependent. We report in this paper that respiration does not shutoff in a recF strain at 37 and 30 degrees C. an srfA mutation suppresses this lack of respiration shutoff effect in a recF srfA mutant at 30 degrees C but not at 37 degrees C; no suppression by this mutation occurs at either temperature in a recF recBC sbcB strain. An srfA strain also does not shut off its respiration at 37 degrees C and shows a temperature conditional UV-induced respiration shutoff response at 30 degrees C. The srfA mutation is thought to cause an altered RecA protein to be produced and we suggest that at 37 degrees This altered protein is temperature sensitive. We conclude from the results in this paper that the recF gene product is required for UV-induced respiration shutoff and that the RecA protein plays a special role in the induction process.