PHYSIOLOGICAL, MORPHOLOGIC AND BEHAVIORAL-RESPONSES OF PERPETUAL CULTURES OF CAULOBACTER-CRESCENTUS TO CARBON, NITROGEN AND PHOSPHORUS LIMITATIONS

Perpetual cultures of Caulobacter crescentus were maintained in a chem ostat and provided with media that provided glucose, glutamate, ammoni um chloride, and Na/K phosphate as sources, respectively, of C, of C a nd N, of N and of P. All cultures were maintained at the same relative flow rate, fN, so that reproductive rate was constant, As the C:N:P r atio was shifted from a balanced ratio of 100 mu g C: 9-10 mu g N: 1 m u g P, the cells modulated their rates of uptake, reducing the rates o f uptake of excess element-sources and accelerating the uptake of pote ntial sources of the limiting element, The change in N-limited cells w as the greatest, resulting in a nearly 150-fold increase in rate of up take of amino acids. Poly-beta-hydroxybutyrate or polyphosphate was st ored whenever C or P, respectively, was not the limiting element, Dire ct measurement of cell and stalk surface areas on purified peptidoglyc an sacculi of beta-limited cells revealed that the surface of both swa rmer and stalked cells, as well as the stalk surface, participated in the accelerated rate of phosphate uptake, Swarmers from W-limited popu lations were the only cells that exhibited chemotactic responsiveness- to methionine, NH4Cl and glutamate, but not to glucose or phosphate-su fficient to be detectable in a microcapillary assay, In populations th at were C-limited and provided with ammonium ions as the principal sou rce of N, morphogenesis and reproduction deteriorated and a steady sta te could not be maintained, Generally, the responses of C. crescentus were appropriate to manage unbalanced nutrient supplies, but this olig oheterotrophic organism did not tolerate excesses of inorganic nutrien ts when limited for its sources of C, of energy, and of ammonium accep tor.