Reconstruction of Escherichia coli mrcA (PBP 1a) mutants lacking multiple combinations of penicillin binding proteins

Previously, we constructed a set of mutants from which eight penicillin bin ding protein (PBP) genes were deleted in 192 combinations from Escherichia coli (S. A. Denome, P. K. Elf, T. A. Henderson, D. E. Nelson, and K. D. You ng, J. Bacteriol. 181:3981-3993, 1999). Although these mutants were constru cted correctly as determined by restriction mapping and the absence of rele vant protein products, we recently discovered by PCR mapping that strains f rom which mrcA (PBP 1a) was deleted were also missing two neighboring genes of unknown function (yrfE and yrfF). We created a new deletion mutation in mrcA and reconstructed 63 strains lacking PBP 1a and other PBP mutant comb inations. The new mrcA mutants do not exhibit mucoidy, phage resistance, te mperature sensitivity, growth rate defects, or antibiotic resistance, sugge sting that these phenotypes require the loss of either yrfE or yrfF alone o r in combination with the absence of multiple PBPs.