COMPARATIVE ULTRASTRUCTURE OF ZOOSPORES WITH PARALLEL BASAL BODIES FROM THE GREEN ALGAE DICTYOCHLORIS FRAGRANS AND BRACTEACOCCUS SP.

The chlorococcalean algae Dictyochloris fragrans and Bracteacoccus sp. produce naked zoospores with two unequal flagella and parallel basal bodies. Ultrastructural features of the flagellar apparatus of these zoospores are basically identical and include a banded distal fiber, two proximal fibers, and four cruciately arranged microtubular rootlets with only one microtubule in each dexter rootlet. In D. fragrans, each proximal fiber is composed of two subfibers, one striated and one nonstriated, and each sinister rootlet is composed of five microtubules (4/1), decreasing to four away from the basal bodies. In Bracteacoccus sp., each proximal fiber is a single unit, the sinister rootlets are four (3/1) or rarely five (4/1) microtubules, and each basal body is associated with an unusual curved structure. The basic features of the flagellar apparatus of the zoospores of these two algae resemble those of Heterochlamydomonas rather than most other chlorococcalean algae that have equal length flagella, basal bodies in the V-shape arrangement, and clockwise absolute orientation. It is proposed that these algae with unequal flagella and parallel basal bodies have a shared common ancestry within the green algae.     

Screening of Korean herbal medicines used to improve cognitive function for anti-cholinesterase activity.

Methanolic extracts of seven herbs (Acorus calamus, Acorus gramineus, Bupleurm facaltum, Dioscorea batatas, Epimedium koreanum, Poria cocos and Zizyphi jujuba) used in traditional Korean medicine for improvement of memory and cognition in old age were tested for cholinesterase inhibitory properties using the Ellman colorimetric method. Significant inhibition of the enzyme at 200 microg/ml was observed for extracts from A. calamus and E. koreanum. The possible bases for the reputation of these and the other herbs tested are discussed in the light of previous investigations into their chemistry and biological activity.     

An Improved Enrichment Broth for Isolation of Escherichia coli O157, with Specific Reference to Starved Cells, from Radish Sprouts

An enrichment broth was developed for the efficient isolation of Escherichia coli O157 from radish sprouts. The broth was buffered peptone water containing 0.5% sodium thioglycolate (STG-BPW), which was designed to allow growth of E. coli O157 in starved and unstarved states. However, this medium suppressed the growth of non-carbohydrate-fermenting obligate aerobes whose colonial appearance on sorbitol MacConkey agar containing cefixime and tellurite (CT-SMAC) resembled that of E. coli O157. Both starved and unstarved cells of E. coli O157 experimentally inoculated into radish sprouts were successfully recovered with STG-BPW enrichment in all cases, most of which showed marked disappearance of E. coli O157-like colonies on CT-SMAC.     

Cell separation from high cell density broths of Alcaligenes eutrophus by using a coagulant

Summary Alcaligenes eutrophus was successfully recovered from high cell density broths by pre-treatment with polyaluminium hydroxide chloride silicate as a coagulant at 36–90 mg Al/l. The optimum pH range for cell coagulation was 10–12. Subsequent centrifugation (45×g) and filtration (pore size 0.5 mm) gave a cell recovery of higher than 90%. The energy demand for cell recovery with the coagulant was only 3–11% of that without it.     

Parietochloris incisa comb. nov. (Trebouxiophyceae, Chlorophyta)

A coccoid green alga, Myrmecia incisa Reisigl, was isolated from the soil of Mt Tateyama, Japan. Electronmicroscopy revealed that the organism has pyrenoids sparsely covered with starch segments and traversed by many parallel thylakoid membranes, and zoo-spores with counterclockwise basal body orientation. Due to the presence of these features, we have proposed a reclassification of M. incisa into the genus Parietochloris, Trebouxiophyceae.     

The stability of L-ATC hydrolase participating in L-cysteine production

Summary In the production of L-cysteine from D,L-ATC stability of the relevant enzymes produced byPseudomonas sp. was tested, and strategies to improve the stability of L-ATC hydrolase were investigated in view of water activity and ionic strength. Among the three enzymes which participate in L-cysteine production, i.e., ATC racemase, L-ATC hydrolase, and S-carbamyl-L-cysteine hydrolase, L-ATC hydrolase is the least stable. Various mixtures of salts and sorbitol were added to adjust the water activities of the tested solutions. As water activity decreased from 0.93 to 0.80, the stability of L-ATC hydrolase was sharply enhanced. In the absence of sorbitol the stability of L-ATC hydrolase increased in proportion to ionic strength. Even though enzyme stability was not good at a low ionic strength, it was enhanced by lowering water activity with addition of sorbitol. The half life of L-ATC hydrolase in sorbitol-salt mixtures increased by tenfold to twentyfold compared to that of a control.     

A kinetic model for the deactivation of pyruvate decarboxylase (PDC) by benzaldehyde

To provide further understanding of the biotransformation of benzaldehyde to L-phenylacetyl carbinol (L-PAC), an intermediate in L-ephedrine production, a kinetic model has been developed for the deactivation of pyruvate decarboxylase (PDC) by benzaldehyde. The model confirms that deactivation is first order with respect to benzaldehyde concentration and exhibits a square root dependency on time. The model covers the range of benzaldehyde concentrations 100–300 mM, as it has been shown previously that 200 mM benzaldehyde can produce L-PAC concentrations up to 190 mM (28.6 g/L) using partially purified PDC from Candida utilis.     

Overexpression of the yeast MCK1 protein kinase suppresses conditional mutations in centromere-binding protein genes CBF2 and CBF5

We find that overexpression in yeast of the yeast MCK1 gene, which encodes a meiosis and centromere regulatory kinase, suppresses the temperature-sensitive phenotype of certain mutations in essential centromere binding protein genes CBF2 and CBF5. Since Mck1p is a known serine/threonine protein kinase, this suppression is postulated to be due to Mck1p-catalyzed in vivo phosphorylation of centromere binding proteins. Evidence in support of this model was provided by the finding that purified Mck1p phosphorylates in vitro the 110 kDa subunit (Cbf2p) of the multimeric centromere binding factor CBF3. This phosphorylation occurs on both serine and threonine residues in Cbf2p.