A HIGH CELL-WALL NEGATIVE CHARGE IS NECESSARY FOR THE GROWTH OF THE ALKALIPHILE BACILLUS-LENTUS C-125 AT ELEVATED PH

The structural components in cell walls of three mutants of a facultat ive alkaliphile, Bacillus lentus C-125, defective in certain cell-wall components were characterized in detail. The cell walls of the wild-t ype C-125 were thick and increased in thickness when grown at high ph, Electron microscopy showed that triple layers developed when the bact eria were grown in an alkaline environment. In contrast, cell walls of teichuronopeptide (TUP)-defective mutants consisted of a single layer . For both the wild-type and mutants, the cell-wall concentrations of the acidic structural polymers teichuronic acid and TUP increased with respect to peptidoglycan as culture ph increased. For all four strain s, the anion content of their cell walls was the greatest at high pH. The cell-wall density of the negatively charged compounds (uronic acid s plus l-glutamic acid) was calculated as about 3 and 9 equivalents (l cell wall region)(-1) for C-125 cells grown at pH 7 and 10, respectiv ely. At high pH, the specific growth rates of the two TUP-defective mu tants were much lower than those of the wild-type. It is concluded tha t increased levels of acidic polymers in the cell walls of alkaliphili c bacteria may be a necessary adaptation for growth at elevated pH.