The growth and morphogenesis of bacteria depend upon the ability of bacteria to regulate the synthesis and shape of their murein sacculus (cell wall). This same ability to regulate murein synthesis is reflected in the sensitivity of bacteria to B-lactams antibiotics; bacteria which are not growing are resistant to most penicillin and cephalosporins and conversely bacteria are most sensitive to B-lactams when they are dividing (forming a septum) and synthesizing murein most rapidly. Thus an understanding of how bacteria regulate the enzymes which form their murein sacculus is not only important in understanding their ability to regulate their shape, but also in understanding their sensitivity and resistance to B-lactams. E. coli and its relatives possess a central growth zone where most of the new murein is added to the sacculus and where morphogenesis of the cell takes place. In this region both the murein polymerases and murein hydrolases are most active. The objectives of this study are (1) to determine how the bacterium inhibits the activity of these enzymes outside the central growth zone (2) and to discover how the growth and morphogenesis of the sacculus is controlled within the growth zone: (1) Recently evidence has been accumulating that the murein outside the growth zone is altered in its chemistry making it resistant to the murein hydrolases and polymerases; examination of this murein with infrared, x-rays and murein hydrolases should reveal some of the bases of the resistance. (2) According to current theories of cell wall growth new murein should be added to the inner surface of the sacculus, and then intercalated into the outer stress-bearing layer of the sacculus; at this point it should become stretched as it comes to bear the stress of osmotic pressure. Using the oligopeptide permease of E. coli the murein of these bacteria can be specifically labelled with deuterated cell wall peptides. With the aid of neutron scattering, these peptides can then be used as probes to study whether this sequence, causing the nascent murein to bear stress prematurely, and help explain the morphogenetic effects of these antibiotics. Chloramphenicol, which prevents growth of the cell and expansion of the sacculus, should have the opposite effect and delay or prevent this transition.
