The Biochemical Requirements for Bacterial Division

Abstract

We are searching for biochemical events related to the process of bacterial division. Data obtained with intact bacteria, using inhibitors primarily, suggest that protein synthesis must occur through most of the division cycle in order that a bacterium can divide a t the end of the cycle. Hence, one approach is to look for a protein that is made throughout the division cycle and whose production is related to ability of the bacteria to divide. Dr Masayori Inouye modifled the ability of the bacterium Escherichiu eoli to divide, using mutants, inhibitors or nutritional deficiencies, and then looked for alterations in the pattern formed by electrophoresis of membrane proteins on polyacrylamide gels. One protein peak on the gels was strongly increased whenever the cells were prevented from dividing. We named this protein "X" ; it has a molecular weight of about 50000.A role was sought for the protein made throughout the cycle but showing its effect only a t the end. Earlier observations by Dr HeleneSmith showed that brief heating of the bacteria (16 min a t 45 "C) produced synchronous cell division; heating delayed division in a way suggesting that a protein needed €or division had been damaged and must be resynthesized before division occurs. Damage to this protein causes the cells to swell; this swelling appears to be the prime basis for the delay of cell division, as shown recently by Dr Po Chi Wu. The swelling caused by an osmotic shift similarly delayed cell division; a result that is support for this hypothesis. A model is proposed for the role of the X protein as a sort of "girdle" that must be built up during the cycle, and that constricts the cells a t the time of division.The past twenty years or so have witnessed a shift in interest among biochemists from the elucidation of steps of metabolism to attempts to put these steps together into patterns. Eventually we want to understand the means by which the individual metabolic pathways are integrated into the functioning of the entire organism. Sir Hans Krebs, in whose honor this lecture was given, has been a pioneer in the organization of enzymological reactions into pathwayswitness the cycles of urea production and carboxylic acid oxidation that bear his name. More recently he has been a prime mover in attempts to understand the control of utilization of metabolities for energy production work that we present our effort to discover the coordinated biochemical events that bring about the complex process of cell division.I n our work we have started with studies of division of the bacterium Escherichiu coli. Bacteria divide, evidently. This phenomenon presents an obvious challenge to bacteriologists, being so fundamental to the evolutionary primary goal of bacteria to multiply their numbers. The problem has three appealing features for me as a biochemist with biological leanings. First, it is a problem of control in space and time. The consistent timing and partioning of the cell division apparatus (the cross wall) and of the DNA occurs smoothly under the mos...

Model for regulation of Escherichia coli DNA repair functions.

“…A correlation between production of protein X and inhibition of cell division was also noted (ref. 20; unpublished results), suggesting a possible role of protein X in cell division also. Only tim-i mutants make protein X at 410 and yet divide normally (manuscript in preparation).…”