Hajime Kadota

Growth Patterns and Substrate Requirements of Naturally Occurring Obligate Oligotrophs

Eighteen strains of obligately oligotrophic bacteria that grow in a medium containing 1 mg of organic carbon per liter and do not grow in a rich medium (5 g/liter of nutrient) were isolated as dominant organisms from the oligotrophic water of Lake Biwa. The growth properties of these, especially of five strains, were examined. The maximum cell yield ranged from 8.5×104/ml to 2.3×106/ml, and their doubling times ranged from 6.6/h to 11.8/h in LT10−4 medium (0.5 mg trypticase and 0.05 mg yeast extract in 1 liter of filtered and aged lake water). They also showed good growth in lake water medium without adding nutrients. The optimum concentrations for their growth were 5 mg/1, 5–50 mg/1, 50 mg/1, or 500 mg/1, depending on the strains. They utilized glutamate, glycine, serine, and glycolate, but not acetate, proline, or leucine. Several properties were examined. Their growth properties were very different from those of oligotrophs or oligocarbophiles isolated by other researchers.

Growth and uptake kinetics of a facultatively oligotrophic bacterium at low nutrient concentrations.

In oligotrophic waters, not only community structure but also physiological properties of heterotrophic bacteria are influenced by the concentration of organic matter.The relationship between growth rate of two facultatively oligotrophic strains ofAeromonas sp. No. 6 andFlavobacterium sp. M1 was studied in comparison with that of two eutrophic strains ofEscherichia coli 7020 andFlavobacterium sp. M2. These strains had two or three different substrate constants (Ks values) depending on substrate concentrations: Ks values for the two former were remarkably lower than those for the two latter. For instance, Ks value forAeromonas sp. No. 6 was about 8.9μM when substrate concentration was greater than 53μM and about 1.1μM when substrate concentration was less man 53μM. InE. coli the Ks value was about 260μM at greater than 5600μM and about 47μM at less than 5600μM substrate concentration.Uptake kinetics ofAeromonas sp. grown in a medium containing 2.7 mM glutamate (H-cell) and 0.11μM glutamate (L-cell) have been determined for the intact cells. H-cell had two distinct values of Km for glutamate assimilation and respiration, and L-cell had three distinct values of Km for glutamate assimilation and respiration: In H-cell Km of assimilation was 2.8×10−7 M and 1.5×10−4 M, and Km of respiration was 2.3×10−7 M and 1.7×10−4 M; in L-cell Km of assimilation was 7.4×10−8 M, 8.3×10−6 M, and 1.3×10−4 M, and Km of respiration was 2.5×10−7, 8.9×10−6M, and 1.7×10−4 M. More than 60% of glutamate taken up by the H- and L-cells was respired when the substrate concentration was less than 10−6 M, although at greater than 10−6 M, 50% and 30% of glutamate was respired by H-cells and L-cells, respectively. These results suggest that the facultatively oligotrophic bacteria grow with high efficiency in environments with extremely low nutrient concentration, such as oligotrophic waters of lakes and ocean, as compared with in their growth in conditions of high nutrient concentraton, such as nutrient broth.

Germination-induced repair of single-strand breaks of DNA in irradiated Bacillus subtilis spores

Abstract The single-strand breaks produced in DNA of B. subtilis spores by ionizing radiation were repaired during germination in the absence of normal DNA synthesis. This repair did not occur unless the initial stage of germination was induced.

Isolation and Characterization of an Apurinic Endodeoxyribonuclease from the Anaerobic Thermophile Desulfotomaculum nigrificans

An endodeoxyribonuclease specific to apurinic sites in DNA was purified 12000-fold from vegetative cells of the anaerobic thermophilic bacterium, Desulfotomaculum nigrificans strain IFO 13698. The enzyme specifically hydrolyses phosphodiester bonds of apurinic double-stranded DNA, without action on normal, alkylated, or single-stranded depurinated DNA. The endodeoxyribonuclease has a molecular weight of about 18500 and a sedimentation value of 2.2S. The enzyme has an optimum pH of 7.5.80 and an optimum temperature of 55 °C. The half-life of purified enzyme is 55 min at 60 °C but it can be heated at 60 °C for at least 60 min without loss of activity in the presence of BSA. The purified enzyme has an absolute requirement for Mg2 + or Mn2+, and is inhibited by EDTA. Enzyme activity is completely inhibited by 0-5 M-NaCl or 1 mM-p-chloromercuribenzoate. All these properties differ from those of apurinic/apyrimidinic endodeoxyribonucleases isolated from Bacillus subtilis, Bacillus stearothermophilus. and Escherichia coli.

Effect of glycine, threonine, and homoserine on the recovery of heat-injured spores of Bacillus subtilis

The spores of Bacillus subtilis which were injured by heat treatment at 90°C for 10min were not able to germinate in Demains minimal agar medium. The injured spores, however, underwent recovery and germinated when the medium was supplemented with glycine, threonine or homoserine. These auxotrophic characters were genetically inherited.

Effects of Some Postirradiation Treatments on the Survival of Bactria Irradiated with 60Co Gamma Rays-I

A fixed quantity of several of the food microorganisms and Escherichia coli were irradiated by means of cylindrically arranged 39 pieces of pencilled- shaped Co60 sources (2100 c) from 30 to 720 kr. The post-irradiation effects on the surviving bacteria are described. The results with respect to dose and pH varied with the different species. However, the effects generally decreased with an increase in the variety of nutritional substance required for bacteria.

Microbiological Studies on the Weakening of Fishing Nets-VIII

The present study is concerned with the taxonomy of marine cellulose-decomposing bacteria belonging to genus Cytophaga. A large number of crude cultures of marine cellulose-decomposing Cytophaga obtained from sea water, bottom mud, or fishing nets submerged in Maizuru Bay, were parely isolated by plating procedure. These isolated bacteria were differentiated to two species and one variety after detailed taxonomical studies. Of these, one species and one variety did not appear to have been described previously, the names Cytophaga rosea nov. sp. and Cytophaga haloflava var. nonreductans nov. var. were proposed. The remaining one species was Cytophaga haloflava which have already been described by the author in part III. Characteristics of Cytophaga rosea nov. sp. and Cytophaga haloflava nonredvctans nov. var. were described. By use of the primary characters listed, a new key to all known species of genus Cytophaga has been constructed.

Studies on the Agar-decomposing Enzyme of Vibrio purpureus

As for the agar-decomposing enzyme, previous works (Gran, 1902; Oshima, 1931; Mori, 19-39) have merely been concerned with the existence of such enzyme in some kinds of organisms, and, therefore, our knowledges of this matter are far from being satisfactorily unders tood. Such being the case, the present author attempted this study from various standpoints in order to clearly made out chemical behaviors of this enzyme in some extent. In the first place, factors affecting the activity of the enzyme of a kind of marine bacteria Vibrio purpureus were preliminarily studied in the following procedure: 1) A semifluid medium, 0.2 per cent agar, was incubated at 25°C after being inoculated with an active culture of Vibrio purpureus. Afer 96 hours, incubation the culture was filtered by Chamberands Filter and it was used as the crude preparation of the enzyme. 2) The effects of temperature and pH value on the activity of the crude enzyme preparation described above were studied by estimating the amount of reducing sugar produced or by measuring the decreasing rate of relative viscosity. The results obtained are illustrated in Fig. 1 and Fig. 2. From the data it seems very probable that the optimum temperature is at around 40°C and the optimum pH value is approximately 6.0 3) The decomposing process of agar-agar by the crude enzyme preparation was observed by the following method: Reducing sugar and relative viscosity of the reaction mixture (0.3 per cent agar solution 40 Occ+McIlvaines buffer solution of pH 6.0 200cc) were determined after various period of reaction at 40°C. The results obtained are shown in Fig. 3. The velocity constant of the reacton calculated from this results by using the monomolecular equation was shown in Table I. From this table it is obvious that the rate process obeys the monomolecular reaction within a certain limited range. 4) The effect of NaCI upon the activity of the enzyme solution which had previously been dialysed in running water for five days dy using the collodion membrane was observed by the usual method. The results obtained are illustrated in Fig. 4. From the data it was found that the optimum concentration of NaCI for the actvity of the enzyme is nearly 3.5 per cent.