Analysis of bacterial populations in a grassland soil according to rates of development on solid media

Abstract The process of colony formation by bacteria from grassland soil sampled in April, July and September was simulated by a colony-forming curve (CFC). The CFC was a super-imposition of several component curves (cCFC) given theoretically by the first order reaction (FOR) model [3,6]. The pattern of FOR model curves was not influenced by the time of sampling and four cCFCs were always recognized during an incubation period of 160 h. It was considered that the CFC describes an inherent property of the bacterial population of the field. Bacterial isolates were obtained from colonies produced in each of four cCFCs on agar plates. Isolates corresponding to one cCFC were classified as one group. The bacterial isolates were characterized by morphological and physiological tests and subsequently clustered. Few oligotrophic bacteria were obtained among bacteria which produced visible colonies within 63 h of incubation time. On the other hand, approx. 50% of bacteria which produced v colonies after 63 h were oligotrophic bacteria. The time required for the appearance of the first colony, t _r of the FOR model, was very similar in the isolates belonging to one group. A close linear relationship was observed between t _r value and doubling time of isolates.     

Morphology,physics, chemistry and biology of Lake Rara in West Nepal

A survey of oligotrophic Lake Rara, the biggest lake in Nepal, was carried out from 1982 till 1984. Mean depth is 100 m, and maximum depth is 167 m. The surface area covers 9.8 km², and the lake contains 0.98 km³ volume of water. Transparency was about 16 m, photoquantum yield decreased exponentially with depth below 5 m, and the extinction coefficient was 8.3 × 10⁻². The concentration of Chl.-a was in the range of 0.06–0.46 mg m⁻³, and total nitrogen was 18–30 μg 1⁻¹. The whole water column was well oxygenated. Primary productivity was extremely low. It has more than 30 inflowing brooks and one outlet. The water quality of the brooks changes drastically with their location. The pH, electrical conductivity, and EDTA hardness in the waters from a landslide area were high. In the waters from a rich pine forest they were extremely low. The zooplankton consisted of two species of protozoa, five species of rotifers, two species of Cladocera, and two species of Copepoda. The zooplankton density range was 6200–16200 individuals m⁻³. The minimum was on November 11th, 1983 and the maximum on August 19th, 1983.     

Evidence for involvement of tryptophan residue in the low-affinity saccharide binding site of ricin D

The nature of the saccharide-binding site of ricin D, which is a galactose- and N-acetylgalactosamine-specific lectin, was studied by chemical modification and spectroscopy. With excitation at 290 nm, ricin D displayed a fluorescence spectrum with a maximum at 335 nm. Upon binding of the specific saccharides, the spectrum shifted to shorter wavelength by 3 nm. However, binding of galactosamine and N-acetylgalactosamine failed to induce such a change in the fluorescence spectrum. The interaction of ricin D with its specific saccharides was analyzed in terms of the variation of the intensity at 320 nm as a function of saccharide concentration. The results indicate that the change in the fluorescence spectrum induced by saccharide binding is attributable to the binding of saccharide to the low-affinity (LA-) binding site of ricin D. The cytoagglutinating activity of ricin D decreased to 2% upon modification of two tryptophan residues/mol with N-bromosuccinimide at pH 4.0, but in the presence of galactose or lactose one tryptophan residue/mol remained unmodified, and a fairly high cytoagglutinating activity was retained. Galactosamine and N-acetylgalactosamine did not show such a protective effect. Spectroscopic analyses indicate that the decrease in the cytoagglutinating activity of ricin D upon tryptophan modification is principally due to the loss of the saccharide binding activity of the LA-binding site. The results suggest that one tryptophan residue is essential for saccharide binding at the LA-binding site, which can bind galactose and lactose but lacks the ability to bind N-acetylgalactosamine and galactosamine.     

IgE heavy chain constant region genes in atopic dermatitis and senile erythroderma patients

By Southern hybridization using a genomic DNA fragment carrying a human IgE heavy chain constant region gene (C ) as a probe, we analyzed the organization of human C genes and their flanking regions in 23 atopic dermatitis and 6 senile erythroderma patients with elevated serum IgE levels, and 6 atopic dermatitis patients with normal IgE levels. On Barn HI, Hind III, and Eco RI digestions, we detected three hybridizable fragments containing three human C genes, C 1, C 2, and C 3, respectively, in all leukocyte DNAs. These fragments were almost identical in size among patients and healthy donors. Pst I digestion generated a genetic polymorphism. We, however, could find no correlation between this polymorphism and the disorders. It was concluded that among the patients and healthy donors, there was no marked difference in the organization of the functional C gene and its flanking region containing a class switch region. Our conclusion cannot rule out the presence of genetic abnormalities of this region in some atopic dermatitis patients which are not resolvable by our method. In the course of this study, we found a novel C -like gene in placenta DNA which differs from the three C genes commonly present in normal human DNA.     

The Escherichia coli cytochrome b556 gene, cybA, is assignable as sdhC in the succinate dehydrogenase gene cluster

Abstract The cytochrome b556 -deficient mutant Escherichia coli K12 strain TK3D11 [7] could not grow with succinate as the sole carbon source, but could grow well on dl -lactate. This finding suggested that cytochrome b556 is primarily responsible for oxidative metabolism and utilization of succinate. 24 Amino acid residues at the amino-terminal of purified cytochrome b556 were determined. This sequence coincided completely with amino acid residues 4 to 27, predicted from the DNA sequence of the sdhC gene, one of the unassigned open reading frames of the sdh gene cluster recently reported by Wood et al. [16]. Based on these and other results, we concluded that cybA , the gene for cytochrome b556 , is assignable as sdhC .     

Binding and cytotoxicity of Ricinus communis lectins to HeLa cells, Sarcoma 180 ascites tumor cells and erythrocytes

The binding of Ricinus communis lectins to HeLa cells, Sarcoma 180 ascites tumor cells and human erythrocytes was studied in detail. Scatchard plots of binding of 125I-lectins to these cells gave biphasic lines except for HeLa cells at 0 degree C. The association constants of lectins for the three cell types at 37 degrees C were lower than those at 0 degree C. The numbers of total binding sites were estimated to be 7 to 16 X 10(7) per HeLa cell, 3 to 4 X 10(7) per Sarcoma 180 ascites tumor cell and 0.4 to 1 X 10(6) per erythrocyte. A fraction, 16 to 27% of the total amount of cell-bound lectin at 37 degrees C, appeared to be bound irreversibly as judged by non-removal on washing with 0.1 M lactose, whereas no lectin was irreversibly bound at 0 degree C. In the case of erythrocytes, no lectin became irreversibly bound even at 37 degrees C. The toxicity of lectins on HeLa cells and Sarcoma 180 ascites tumor cells was investigated. The toxicity of ricin D was 50 times for Sarcoma 180 ascites tumor cells and 140 times for HeLa cells as much as that for castor bean hemagglutinin. As to the sensitivities of both cell types to these lectins, it became apparent that Sarcoma 180 ascites tumor cells were more susceptible than HeLa cells.     

Differences in Ca2+ mobilization induced by alpha-adrenergic agonist and phosphatidic acid in cultured hepatocytes

In an attempt to elucidate the relationship between phosphatidylinositol breakdown and alpha-adrenergic responses, effects of phosphatidic acid and phosphatidylinositol related metabolites on Ca²⁺ mobilization and glucose output in cultured hepatocytes were examined. Norepinephrine induced the net ⁴⁵Ca²⁺ efflux from preloaded cells and stimulated glucose output via alpha-adrenergic receptor stimulation, whereas phosphatidic acid caused ⁴⁵Ca²⁺ uptake to cells and did not stimulate glucose output. Myo-inositol-monophosphate, diglyceride and arachidonic acid, which are released by phosphatidylinositol breakdown, had no effect on ⁴⁵Ca²⁺ efflux and glucose output in cells. These results suggest that phosphatidic acid and phosphatidylinositol related metabolites can not mimic the alpha-adrenergic actions in cultured hepatocytes.     

Influence of predation on species coexistence in Volterra models

The possibility of predator-mediated coexistence of all species in model ecosystems of the Volterra type is discussed, that is, asymptotic behaviors of systems of two competing species are analyzed when one or two predators are added. All species in the communities can coexist in two distinct ways mathematically, that is, the species may coexist at equilibrium or may coexist in persistent oscillations. The stability of all species at equilibrium increases when one or two predators are added. The conditions for oscillatory coexistence in limit cycles or in chaotic behaviors of two-predator systems are more complicated than in those of one-predator systems. It is concluded that predator-mediated coexistence can be promoted by an intimate relationship between the competitive ability of the prey and the diet preference of the predators.     

Chromosomal location of the Escherichia coli cytochrome b556 gene, cybA

Summary The amounts of cytochrome b556 in the cytoplasmic membranes of several Escherichia coli K12 strains having F-prime factors and a lambda transducing phage were determined. The amount was amplified about two-fold in strains having F100-12 and F152, but not in strains having F100-11, F8 and psu ⁺ 2glnS ⁺. The strain TK3D11, which lacks the kdp-gltA region (deletion D-01) of the E. coli chromosome, did not synthesize cytochrome b556 at all. From these results, the gene cybA encoding cytochrome b556 was located in the kdp-gltA region.In the cytochrome b556-deficient mutant, a novel b type cytochrome, cytochrome b561 which is a product of the gene cybB, was identified. It seems to function as a physiological electron transferring cytochrome in place of cytochrome b556 in this mutant.Abbeviations HPLC high performance liquid chromatography - EDTA ethylenediamine tetraacetic acid - SDS sodium dodecyl sulfate - NADH reduced form of nicotinamide adenine dinucleotide