SUMMARY: It is argued that the average motility of bacterial populations should be identified with a diffusivity parameter. A simple capillary assay for quantifying this parameter is described, and some results obtained by using this procedure are presented. It is concluded that the assay combines speed and simplicity of operation with sufficient accuracy to make it a valuable tool in the assessment of motility.
SUMMARY: Six strains of Haemophilus species, pathogenic to chickens, required 1.0 to 1.5% (w/v) NaC1 for optimum growth. The requirement was for Na+ rather than NaCl. A sodium salt buffer influenced the optimum NaCl requirement and enhanced growth. Each strain required a different concentration of NADH for an optimum rate of growth.
SUMMARY: Myxamoebae of Dictyostelium discoideum strain Ax-2 were adapted to growth in a medium containing B vitamins, a vitamin-free tryptic digest of casein, soluble starch and inorganic salts. Omission of vitamins from this medium confirmed that D-biotin, thiamin, folate and a-lipoate are essential for myxamoebal growth and showed that riboflavin or flavin mononucleotide is also required. No requirement for other vitamins or growth factors could be detected. A defined medium was developed by replacement of the tryptic digest of casein with a mixture of 20 L-amino acids and addition of Tween 80. Tween 80 caused starch precipitation in the medium and this seemed essential for stimulating growth of the myxamoebae.
SUMMARY: Germination of Syncephalastrum racemosum sporangiospores was studied in shake flask and batch fermenter cultures. In the presence of glucose, spore swelling preceded outgrowth of germ tubes; dry weight increased markedly only at the time of germ tube emergence. Glucose was essential for initiation of these events. Both swelling and germ tube emergence quickly ceased when glucose-grown cultures were shifted down to non-permissive glucose-free medium. Spore swelling was not a prerequisite for germ tube emergence. Analysis of size distributions within populations of partially germinated spores indicated that larger spores germinated first.
SUMMARY: In the presence of K+, Na+ enhanced respiration and activated cellular motility and transport of K+, amino acids and phosphate in Pseudomonas stutzeri. Inorganic phosphate taken up was rapidly esterified to nucleoside triphosphates and diphosphates. Respiration and phosphate transport showed cooperative responses to Na+ which increased with temperature. Respiration was more sensitive to polymyxin B in the presence of Na+. Dinitrophenol and carbonyl cyanide p-trifluoromethoxy-phenylhydrazone stimulated respiration when either Na+ or K+ was absent, but not in the presence of both cations. Therefore, Na+ is essential for the cytoplasmic membrane of P. stutzeri to perform energy-linked functions coupled to respiration.
SUMMARY: The rate of accumulation of ammonium ion in cultures of Ureaplasma urealyti-cum was independent of the growth rate and of the initial urea concentration above 0.025% in the medium, although the quantity of ammonium ion accumulating did depend on the initial urea concentration. Ammonium ions accumulated at a similar rate in U. urealyticum cultures of both rapidly and slowly growing organisms. Viable but non-growing ureaplasmas also produced ammonia in complete medium at a lower temperature than usual (25°) or in an inadequate growth medium at 37 °. The rate of ammonium ion accumulation in a dying culture depended on the number of viable organisms present; this is relevant to diagnostic methods for ureaplasmas which depend on detecting ammonia colorimetrically.