Vibrio sp. strain ABE-1 has two types of NADP+-isocitrate dehydrogenase (IDH-I and -II: EC 22.214.171.124). A mutant defective in IDH-I was isolated by N-methyl-N′-nitro-N-nitrosoguanidine treatment and a new convenient screening method which can directly detect the IDH-I activity of colonies on the screening plates. The direct detection of the enzyme activity was accomplished by coating the colonies with calcium phosphate gel then dehydrogenating in two steps with different tetrazolium salts. An isolate, strain YF-83, completely lacked IDH-I activity, but retained IDH- II activity at a level similar to the parent strain. Strain YF-83 had the same growth characteristics as the parent strain with regard to nutrient requirements and growth temperatures. Therefore, it was concluded that IDH-I is not essential for the growth of strain ABE-1.
Extracellular proteinase activities produced by 36 strains in the genus Monascus were determined at various pHs using casein and Azocoll as substrates. These strains were grouped into three types (A, B, and C) according to the pH-activity profiles of their proteinases. Type A was characterized by only acid proteinases with an optimal pH around 3 and was found in eight strains of six species of Monascus (i.e., M. araneosus, M. fuliginosus, M. kaoliang, M. pilosus, M. pubigerus, and M. vitreus). Type B was characterized by only alkaline proteinases with an optimal pH about 8-9 and was found in 24 strains of nine species and two varieties of Monascus (i.e., M. albidus, M. albidus var. glaber, M. anka, M. anka var. rubellus, M. araneosus, M. kaoliang, M. major, M. purpureus, M. ruber, M. rubiginosus, and M. serorubescens). Type C was characterized by the two kinds of proteinases observed in types A and B and was found in three strains of one species of Monascus (i.e., M. kaoliang). It was revealed in this study that Monascus spp. secreted extracellular alkaline proteinases. However, there was not any considerable correlation between the classification system of the genus Monascus and the type of proteinase produced.
Previously, we demonstrated that nitrate respiration increases the synthesis of iron-containing superoxide dismutase (Fe SOD) in anaerobically grown Escherichia coli cells. In this study, we developed a system with which the anaerobic induction of Fe SOD by nitrate respiration in E. coli was separated from the induction of the nitrate respiration system. The anaerobic induction of Fe SOD required the presence of both nitrate and an electron donor, and the induction of Fe SOD by nitrate respiration was inhibited by chloramphenicol or riphampicin. When glucose was used as the electron donor, carbonyl cyanide p-trifluoro-methoxyphenyl-hydrazone (FCCP) but not N, N′-dicyclohexylcarbodiimide (DCCD) inhibited the induction of Fe SOD by nitrate respiration, but when formate was used as the donor, both FCCP and DCCD inhibited the induction of Fe SOD by nitrate respiration.
Yeast spheroplasts were cultured in several sporulation media, each containing different kinds of inhibitors which affected meiosis, and the morphology of the mitochondrial nucleoids (mt-nucleoids) was examined using the DNA-binding fluorescent dye, 4′, 6-diamidino-2-phenylindole. Adding inhibitors which completely blocked meiosis and sporulation caused the mt-nucleoids to form two distinct morphological types. In the presence of actinomycin D, cycloheximide, methyl 2-benzimidazole carbamate and 2-(4-thiazolyl)-1H-benzimidazole, the mt-nucleoids fused with each other and showed a marked string-like appearance, as did the mt- nucleoids observed in normal sporulation process. In the presence of ethidium bromide, antimycin A, olygomycin, carbonyl cyanide m- chlorophenylhydrazone, mt-nucleoids appeared as fluorescent particles scattered in the cytoplasm. However, adding glucose to the sporulation medium containing antimycin A gave rise to a marked string-like appearance of mt-nucleoids in spite of strong inhibition of respiration. These results indicated that the morphology of mt-nucleoids was not directly associated with respiration itself, but that the preservation of complete mitochondrial DNAs and some metabolic activities related to respiration were required for the formation of string-like mt-nucleoids in sporulation media.
The taxonomic position of a yeast strain Y-128 formerly identified as Torulopsis candida, which effectively assimilates crude palm oil, was reinvestigated. A DNA-DNA hybridization study revealed that this yeast belongs to a hitherto undescribed species. It is described as Candidapalmioleophila Nakase et Itoh sp. nov. The high maximum growth temperature of 41-42°C is a characteristic of this species which differentiates it from Candida famata and Candida saitoana (=Torulopsiscandida).