NORMAL GENOMIC

• Curtis NA, Eisenstadt RL, Turner KA, White AJ
• Inhibition of penicillin-binding protein 3 of Escherichia coli K-12. Effects upon growth, viability and outer membrane barrier function.
• J Antimicrob Chemother. 1985; 16: 287-96
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• A temperature-conditional, cell-division mutant of Escherichia coli K-12 possessing a thermolabile penicillin-binding protein (PBP) 3 was isolated. The mutant phenotype was due to a lesion in the pbpB gene. This mutant, and leu+ pbpB co-transductants of E. coli C600 grew as rods at 30 degrees C but were converted to filaments at 42 degrees C upon denaturation of PBP3 and concomitant cessation of cell division. These strains have been used to study the consequences of the specific inhibition of PBP3 of E. coli K-12 upon growth, viability and outer membrane integrity. Our results indicate that the singular inhibition of PBP3 is bactericidal in E. coli K-12, even though the turbidimetric response of the bacteria in broth culture suggests bacteriostasis. Furthermore, filament formation is accompanied by disruption of outer membrane barrier function, as witnessed by the rapid leakage of periplasmic beta-lactamase. This latter finding was confirmed by observing the lytic effect of a sub-inhibitory concentration of cefsulodin on filaments of E. coli K-12 induced by PBP3-specific beta-lactams. The impact of these results upon the testing of beta-lactam sensitivity of E. coli K-12 is discussed.

• Amanuma H, Strominger JL
• Trapping of the substrate-derived acyl enzyme intermediate of purified penicillin-binding protein 1a of Escherichia coli.
• J Bacteriol. 1984; 160: 824-5
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• Purified penicillin-binding protein 1a of Escherichia coli formed an acyl enzyme intermediate with the highly reactive synthetic substrate diacetyl-L-lysyl-D-alanyl-D-lactate at acid pH, although in extremely low yields.