Eleven strains of yeasts, isolated from galleries of ambrosia beetles in Japan, formerly identified as Pichia acaciae were found to have different sequences in the D1/D2 domain of the large subunit (LSU) rRNA gene. After detailed taxonomic studies including a DNA–DNA reassociation experiment, 11 strains were found to represent a novel species of the genus Pichia. It is described as Pichia porticicola sp. nov. (type strain NBRC 100302T = CBS 11715T). The eleven strains were isolated from various samples associated with different kinds of insects and trees which were collected in 11 prefectures, from the north to the south of Japan. This species might be a common species in galleries of ambrosia beetles in Japan.
Fifteen strains of anamorphic yeasts isolated from various natural substrates collected in various places in Thailand were found to represent two novel species of anamorphic yeast genus Candida based on the sequence analysis of the D1/D2 domain of the large subunit rRNA genes, chemotaxonomic and conventional properties used for the classification of yeasts. These strains are located in the clade including Candida etchellsii and Candida magnoliae. Fourteen strains represented by ST-490T (BCC 15176T=NBRC 106439T= CBS 11674T) are closely related to Candida sorbosivorans in the D1/D2 sequences but 11 nucleotides (2.4%) were substituted. The remaining strain, ST-594T (=BCC 15278T=NBRC 106446T=CBS 11673T) showed a close relationship to Candida geochares but 21 nucleotides (4.7%) were substituted. Apparently, these strains represent two novel Candida species of the Starmerella clade. The two species are described as Candida potacharoeniae sp. nov. and Candida spenceri sp. nov. in the present paper. Like the most species of this clade, the two species contain galactose in the cells in addition to glucose and mannose and have high mol% G + C of 54.4–55.9 and 54.9, respectively.
Variants of bottom-fermenting brewer’s yeast that grew at high temperatures and showed poor proliferation and fermentation at low temperatures were isolated. Similar variants of laboratory yeast were also isolated and found to be incapable of mating. The KEX2 gene was cloned by complementation. It was shown to be responsible for these traits, because a KEX2 disruptant of Saccharomyces cerevisiae (S. cerevisiae) laboratory yeast grew poorly at low temperatures and was resistant to high temperatures. In addition, a Saccharomyces bayanus (S. bayanus)-type KEX2 (Sb-KEX2) disruptant of bottom-fermenting brewer’s yeast grew poorly at low temperatures and was resistant to high temperatures. The KEX2 gene product plays an important role in proliferation of yeast at low temperatures, which is an important trait of bottom-fermenting brewer’s yeast. These findings advance our understanding of the proliferation of yeast at low temperatures, especially that of bottom-fermenting brewer’s yeast.
Strain JA430T is a Gram-negative, vibrioid to spiral shaped phototrophic purple sulfur bacterium isolated from anoxic sediment of a saltern at Kanyakumari in a mineral salts medium that contained 2% NaCl (w/v). Strain JA430T grows optimally at 5−6% NaCl and tolerates up to 12% NaCl. Intracellular photosynthetic membranes were of the lamellar type. Bacteriochlorophyll a and carotenoids of the spirilloxanthin series are present as photosynthetic pigments. Major cellular fatty acids are C18:1ω7c, C16:0, C19:0cycloω8c and C16:1ω7c/C16:1ω6c. Strain JA430T exhibits photoorganoheterotrophy and chemoorganoheterotrophy and requires para-aminobenzoic acid, pantothenate and pyridoxal phosphate for growth. Phylogenetic analysis on the basis of 16S rRNA gene sequence analysis showed that strain JA430T forms monophyletic group in the genus Ectothiorhodospira. The highest sequence similarity for strain JA430T was found with the type strains of Ectothiorhodospira variabilis DSM 21381T (96.1%) and Ectothiorhodospira haloalkaliphila ATCC 51935T (96.2%). Morphological and physiological characteristics discriminate strain JA430T from other species of the genus Ectothiorhodospira, for which we describe this as a novel species, Ectothiorhodospira salini sp. nov. ( = NBRC 105915T = KCTC 5805T).
A dimorphic transition from the yeast form to filamentous one in Candida tropicalis pK233 is triggered by the addition of ethanol into the glucose semi-defined liquid medium and the process of filamentation accompanies temporal depolarization of yeast cells. The transition is completely prevented by further supplementation of myo-inositol at the start of cultivation. The addition of ethanol caused an increase in membrane fluidity during the process of depolarization, and then fluidity was gradually lowered to the level equivalent with that of the stationary-phase yeast cells in accordance with filamentation. The increase in membrane fluidity of ethanol-induced cells appeared parallel with reduction in the content of membrane phosphatidylinositol, which was rich in saturated palmitic acid. Introduction of exogenous myo-inositol or 1 M sorbitol into the ethanol-supplemented culture at the start of cultivation restored yeast growth and the reduction of membrane fluidity occurred, coupled with the recovery of the phosphatidylinositol content.
Ethylene inhibits the establishment of symbiosis between rhizobia and legumes. Several rhizobia species express the enzyme ACC deaminase, which degrades the ethylene precursor 1-cyclopropane-1-carboxilate (ACC), leading to reductions in the amount of ethylene evolved by the plant. M. loti has a gene encoding ACC deaminase, but this gene is under the activity of the NifA-RpoN-dependent promoter; thus, it is only expressed inside the nodule. The M. loti structural gene ACC deaminase (acdS) was integrated into the M. loti chromosome under a constitutive promoter activity. The resulting strain induced the formation of a higher number of nodules and was more competitive than the wild-type strain on Lotus japonicus and L. tenuis. These results suggest that the introduction of the ACC deaminase activity within M. loti in a constitutive way could be a novel strategy to increase nodulation competitiveness of the bacteria, which could be useful for the forage inoculants industry.