No abstract

PsbK is a small membrane protein of the PSII core complex and is highly conserved from cyanobacteria to plants. Here, we studied its role in the thermophilic cyanobacterium, Thermosynechococcus elongatus BP-1, by focusing on a psbK disruptant with hexahistidine-tagged CP47. The psbK disruptant showed photoautotrophic growth comparable with that of the wild type under a wide range of light conditions. The mutant PSII complex retained the oxygen-evolving activity with a unique modification of the acceptor Q(B) site. N-terminal sequencing revealed that Ycf12 and PsbZ proteins were lost in the PSII complex prepared from the mutant. Immunoblotting detected reduced accumulation of PsbZ in the mutant thylakoid. These results suggest that PsbK is required not only for association of PsbZ and Ycf12 with the isolated PSII complex but also for the stabilization of PsbZ in the thylakoid membrane.

Fifty-six strains of Candida albicans (40 fresh human isolates, 10 laboratory strains, and 6 Candida stellatoidea strains), seven strains of other Candida species, and one strain of Saccharomyces cerevisiae were examined for a total of 182 biochemical and physiological characters. As 121 characters proved positive or negative in all of the strains, analysis of similarity values (simple matching coefficients) derived from the remaining 61 characters revealed that C. albicans strains could be discriminated from other species with similarity values of 70% or lower, and that the cluster of C. albicans strains with internal similarity values above 70% could be divided into two subclusters representing classical C. albicans and C. stellatoidea, with intergroup similarity of 70 to 85% and intragroup similarities of 85% or higher. No discernible difference was noted between isolates from pathological speciments and those from healthy individuals.The medically important opportunistic fungus Candida albicans has recently undergone a major taxonomic change, namely, the merger of C. albicans (hereafter referred to as classical C. albicans) and Candida stellatoidea to make the latter a synonym of the former [9, 10]. Although this change was made mainly on the basis of a DNA homology study involving a limited number of strains [9], more extensive experiments employing similar methodology performed in our laboratories fully supported this decision [3]. The coalition of the two species has also been corroborated by a study of the restriction cleavage patterns of their actin genes [8], although a similar study of another locus [6] and analysis of karyotypes [7] have revealed differences between them.Within the species C. albicans thus established, relevant intraspecies classification (subspecies, varieties or types) is still a matter worthy of investigation. At least two overlapping questions must be answered. First, is it possible to differentiate classical C. albicans from C. stellatoidea at a subspecies level? For example, the difference between the antigenic structures of C. albicans and C. stellatoidea is well known [ 16] and the classical and renewed observations that C. stellatoidea strains are less virulent

Genetic relatedness between strains of C. albicans and C. stellatoidea was studied by measuring G + C content and overall sequence homology. G + C contents determined by high-performance liquid chromatography were 32.6 to 34.2% for 26 strains of C. albicans and 33.0 to 33.9% for eight strains of C. stellatoidea. DNA-DNA hybridization with two C. albicans and two C. stellatoidea probes revealed that all 34 test strains formed a single cluster in which the extents of hybridization with the heterologous probes ranged between 77.9 and 105.6% of those with the homologous probes. These results give support to the unification of C. albicans and C. stellatoidea into a single species.

Two strains of Candida albicans were examined for a glucose effect on the catabolism of N-acetylglucosamine. It was shown that the induction of N-acetylglucosamine uptake capacity was almost completely blocked by glucose at 0.5% (w/v), whereas that of N-acetylglucosamine kinase was partially repressed.