Suspension of Escherichia coli adsorbed on an anion-exchange resin, Dowex 1, was incubated in continuously flowing growth medium at D=1, the value being above a critical dilution rate. At D=1, it is possible to follow the growth of adsorbed cells separately from that of free cells since cells freely suspended in the liquid phase of culture are rapidly washed out from the system, though the latter population might be growing under the condition. Cell concentration in the liquid phase of culture at first increased stepwise with regular periodicity (first phase) and secondly kept a steady level in proportion to the initial number of adsorbed cells (second phase). Periodic change of cell concentration in the first phase is explained by division and detachment of new-born cells from the resin surface according to age distribution of adsorbed cells. The length of each period depends on the pH of the medium and reflects the generation time of adsorbed cells. From the level of cell concentration in the second phase, growth rate with adsorbed cells is calculated and it is concluded that the growth rate with adsorbed cells is considerably larger than that with free cells.
Twenty-two strains of Actinomyces bovis, Actinomyces israelii, Actinomycesnaeslundii, Actinomyces odontolyticus, Actinomyces viscosus, and Arachniapropionica were studied by whole cell infrared spectrophotometry. Different spectra were obtained with the cultures grown in brain heart infusion medium and those grown in glycerol Kelner-Morton medium under anaerobic condition. The spectra measured with the test organisms cultivated in glycerol Kelner-Morton medium were compared with those of Streptomyces (Actinomadura), Nocardia, andMycobacterium spp. described previously. All strains of microaerophilic actinomyces showed absorption pattern of Streptomyces (Type B) or Nocardia (Type C) in region I, and that of Streptomyces (Type A) in region II, and absorption pattern of Mycobacterium (Type E) in region IV. An absorption pattern specific to this group of organisms was observed in region III, 1460 to 1385cm-1.
Electrophoresis of the partially purified milk-clotting enzyme produced by Penicillium citrinum with 0.02M acetate buffer (pH 3.42) showed four protein components. Fractionation of the enzyme preparation with acetone led to individual isolation of the four electrophoretic components. The course of proteolysis in the first phase of enzymic action of each of the partially purified fungal enzymes and the four pure fractions was conducted and compared with those of trypsin and calf rennin. The fungal enzyme contained two rennin-like fractions constituting most of the milk-clotting activity with limited proteolysis and another two fractions with less clotting activity and more proteolysis. The macroglycopeptide isolated by the action of the fungal rennin-like enzyme fraction comprised 12 amino acids while its carbohydrate moiety consisted of galactose, galactosamine, and N-acetylneuraminic acid. Further studies on the most active rennin-like enzyme fraction showed that calcium chloride enhanced only the primary stage of the enzymic phase but near the end of this phase the rate of NPN release was very slow.
Taxonomic studies on 32 strains of Candida tropicalis and its allies revealed that they could be divided into two forms. C. tropicalis form I (24 strains) had a GC content of 34.1-34.9%, assimilated soluble starch, had an antigenic structure of 1, 2, 3, 4, 5, 6, and formed wrinkled colonies with hair when they aged. C. tropicalis form II (8 strains) had a GC content of 36.3-36.8%, did not assimilate soluble starch, had an antigenic structure of 1, 2, 3, 4, (5), (6), and formed smooth colonies without hair when they aged. These two forms are also differentiated by the proton magnetic resonance spectra of alkali-extracted mannans. Since taxonomic characteristics of strains of form I are identical with those of the standard description of C. tropicalis, the strains of form II should be represented as a new species. The name Candida subtropicalis is proposed for the strain of form II and the description of this species is given.
A new species Corynebacterium glycinophilum nov. sp. was isolated from a putrefied banana, which is resistant to a high concentration of glycine and has a prominent ability of producing L-serine from glycine. Among various substances supplemented to the medium used, nicotinamide was found to be effective for L-serine production. The L-serine production was in parallel with the consumption of glycine in the medium. Ferrous ion was found to depress L-serine production and to increase the assimilation of glycine added. Glycine was utilized as a nitrogen source in the presence of glucose, but was not utilized as a carbon source in the absence of glucose. The addition of inorganic nitrogen increased L-serine production. Glycine was not formed from L- serine. L-Threonine was formed with L-serine from glycine, probably by serine transhydroxymethylase.
A comparative study on Pichia dispora and Pichia saitoi was made and the results from this investigation seem to confirm them to be a different taxon. The two species differed in the mode of ascus formation, number of ascospores, nature of the ascus, and in the guanine-cytosine content in DNA but not in other biochemical characteristics. Such morphological characteristics in sexual reproduction are considered to be better keys for differentiating these two taxa than assimilability of ribitol in which a difference was formerly found between them.