An algophorous amoeba, a species in the genus Nuclearia, was isolated from a eutrophic lake in Japan. The floating form with extremely fine radiating pseudopodia has a mean diameter of 12.5μm. The characteristic shape of this isolate is subspherical or flattened and no motile form was observed. The nucleus contains a lobed central nucleolus. Fourteen strains of bacteria, cyanobacteria and green algae were tested as prey for the isolated amoeba. There was considerable variation in the rates of their utilization. The high rates of predation by the amoeba suggest that it may be of importance in the food chains and nutrient recycling in aquatic habitat.
The inhibitory effects of aflatoxin B1 on growth, respiration and cell viability were studied in Escherichia coli, Salmonella typhi, L forms of S. typhi B-34-6 and protoplasts of E. coli and S. typhi. Tween-80 (0.05% v/v) or EDTA (0.05% w/v) accentuated the lethal effects of aflatoxin B1 in test organisms. The protoplasts and L forms were more sensitive than the parent strain to the inhibitory effects of aflatoxin B1. Cells from all growth phases were equally susceptible to the growth inhibition. The E. coli and S. typhi cells bound approximately 10-24% more aflatoxin B1 with Tween-80 (0.05%) or EDTA (0.05%) added than with aflatoxin B1 alone. Aflatoxin B1 caused a substantial decrease in oxygen uptake in test preparations and this decrease was greatest in the L forms of S. typhi, followed by protoplasts, protoplast membranes, whole cells and cell debris.
A description of a new nitrate-positive Cryptococcus species is given. The new yeast species is considered to be representative of the apparently related group of species comprising Cryptococcus terreus, Cryptococcushimalayensis and Cryptococcus elinovii. A new key is presented for the identification of all nitrate-positive Cryptococcus species described to date.
The rhodoquinone (RQ) composition was studied in representatives of 20 species of Rhodospirillaceae. Thin-layer chromatography, ultraviolet spectrophotometry, mass spectrometry, and high-performance liquid chromatography revealed that six of the 20 test species contained RQ as a major quinone in average amounts of 0.28 to 2.22μmol per g dry weight of cells. The predominant homologue of RQ in the six species was as follows: RQ-8-Rhodospirillum photometricum and an unknown species resembling Rhodocyclus gelatinosus; RQ-9+RQ-10-Rhodopila globiformis; RQ-10-Rhodospirillum rubrum, Rhodopseudomonas acidophila, and Rhodomicrobium vannielii. The taxonomic significance of RQ and other isoprenoid quinones is discussed in comparison with the new classification system for the phototrophic bacteria recently proposed by IMHOFF et al.
Ten strains designated as Planococcus halophilus, three strains of Planococcus sp. Group III, and an unidentified motile coccus were studied taxonomically. They all had meso-diaminopimelic acid in the cell wall, DNA base composition ranging between 43.9 to 46.6%, menaquinone systems with MK-7, and growth at a concentration of 20% of sodium chloride. These characteristics differ significantly from those of the type species (Planococcus citreus) of the genus Planococcus. Therefore, we regard these strains as belonging to a new genus, and propose the genus Marinococcus for such bacteria. Two species are recognized in this genus, Marinococcus albus sp. nov. and Marinococcus halophilus (Novitsky and Kushner) comb. nov. They differ from each other in colony pigmentation, oxidase, urease, extracellular DNase, nitrate reduction, hydrolysis of gelatin, casein and esculin, and production of acid from glucose and some other sugars. Marinococcus halophilus comb. nov. is the type species of the genus Marinococcus. Strain HK 718 (=CCM 2706, Czechoslovak Collection of Microorganisms, Brno, Czechoslovakia=IAM 12844, Institute of Applied Microbiology, University of Tokyo, Japan=JCM 2479, Japan Collection of Microorganisms, Wako, Japan) is the type strain of M. halophilus, and strain HK 733 (=CCM 3517=IAM 12845=JCM 2574) is the type strain of Marinococcus albus.
Motile cells are released into liquid media from the aerial mycelia of Actinosynnema pretiosum subsp. auranticum strain N-1001 and from the substrate mycelia of its bald mutant N-1039. These cells are initially without flagella and are non-motile. Functional flagella of cells from the aerial mycelia develop after 60min of incubation at 28°; the cells then become motile. Substrate mycelia cells become motile after 45min of incubation. Flagella formation and cell motility in both aerial and substrate mycelia require exogenous amino acids; cells incubated with water alone rarely become motile. Rifampicin and chloramphenicol inhibit the formation of flagella in these cells. This suggests that the expression of genes involved in the flagella formation is triggered by aquatic environments with exogenous amino acids.
Two fragments from yeast mtDNA were cloned. One fragment had ARS activity and the other was devoid of it. These two fragments were sequenced. The ARS activity in the former was confined within the 151 bp sequence which is a neighbor of the ori/rep sequence. In spite of its ARS activity, this fragment lacked the consensus sequence A/TAAAPy-ATAAAT/A the same as the 186 bp sequence as we previously reported (J. Biochem., 95, 589-592, 1984). In contrast, the latter fragment had a consensus sequence but it lacked ARS activity. In comparing the two sequences, the necessary elements for yeast mitochondrial ARS are considered.
Two isozymes of NADP-specific isocitrate dehydrogenase (EC 188.8.131.52) were purified from the obligately psychrophilic marine bacterium Vibrio sp, strain ABE-1. Isozyme I purified by Blue-Sepharose column chromatography (Mr=about 85kDa) was proved to consist of two subunits (Mr=ca. 42kDa) by sodium dodecyl sulfate polyacrylamide gel electrophoresis and cross-linking with dimethyl suberimidate. Isozyme II purified by NADP-Sepharose column chromatography was a single large polypeptide (Mr=ca. 85kDa). This extremely thermolabile isozyme was easily inactivated above 15° and reactivated by chilling at 0° in the presence of 2-mercaptoethanol. Even when inactivated completely at 40° it could be renatured to about 40% of the original activity under the appropriate conditions. Isozyme I once denatured could not be renatured.
Auxotrophic mutants of an asporogenous yeast strain, Candida maltosa IAM12247, were selected after mutagenesis. In spite of our efforts to generate an array of auxotrophic mutants, only two groups of adenine. auxotrophs, histidine auxotrophs and leucine auxotrophs, were obtained. The nuclear DNA content of this species was measured by fluorescent microscope photometry. By this criterion and UV light irradiation inactivation experiments, C. maltosa was found to contain the same ploidy level as diploid strains of Saccharomyces cerevisiae. Unstable intraspecific and intergeneric prototrophic hybrids were obtained by the fusion between auxotrophic mutants of C. maltosa or between auxotrophic mutants of C. maltosa and S. cerevisiae. The stability and relative DNA content of these prototrophic hybrids are compared.
The enzymes in ammonia assimilation pathways have been examined in a strictly anaerobic bacterium Bacteroides fragilis. The activities of NADPH- and NADH-linked glutamate dehydrogenase and glutamine synthetase were demonstrated in extracts of cells, but very low activity of NADPH-dependent glutamate synthase and no activity of alanine dehydrogenase were demonstrated. Both activities of the glutamate dehydrogenase were not distinguished electrophoretically, indicating the presence of a dual pyridine nucleotide-specific enzyme. At low concentrations of ammonia in batch cultures and at low dilution rates of continuous flow cultures, higher activities of glutamate dehydrogenase were found in the cells. The values of Km of NADPH-linked glutamate dehydrogenase were 0.8mM, 0.15mM, and 7μM for ammonia, 2-oxoglutarate, and NADPH, respectively. Although glutamine synthetase activity was also higher in cultures with limited ammonia and at low dilution rates of continuous cultures, this enzyme may not be important for ammonia incorporation into amino acids, since cell growth was not affected by the addition to the culture of methionine sulfoximine, a glutamine synthetase inhibitor. This evidence suggests that ammonia assimilation is mainly carried out by the glutamate dehydrogenase in B. fragilis.
Two β-glucosidases from Candida wickerhamii were studied. One is parietal and exocellular, the other is endocellular. Both enzymes were purified by ion-exchange chromatography and gel filtration. They could hydrolyze glucosides with β(1-3), β(1-4) and β(1-6) configurations. The exocellular enzyme is active against soluble cellodextrins (D.P 3 to 6). This is responsible for the ability of the Candida wickerhamii strain to ferment soluble cellodextrins. Both enzymes were constitutive, but their biosynthesis was repressed by glucose.