Novel ecological niche of Cetobacterium somerae, an anaerobic bacterium in the intestinal tracts of freshwater fish

AIMS: This study was conducted to clarify the taxonomic status of Bacteroides type A strains with high vitamin B(12)-producing ability that is widely distributed in the intestinal tracts of freshwater fish. METHODS AND RESULTS: Seventeen strains of Bacteroides type A isolated from five fish species were all rod-shaped and gram-negative. The strains were positive for esculin hydrolysis, nitrate reduction, resistance to bile, acid phosphatase, and negative for the production of catalase and urease and the susceptibility to vancomycin. The G+C content of DNA from the 17 strains was 29 x 1-31 x 9 mol%, and 16S rDNA sequence analysis revealed a close phylogenetic relationship between Bacteroides type A strains and Cetobacterium somerae sharing 99 x 7-100% sequence similarity. In addition, strains were capable of producing vitamin B(12) at a rate of 1 x 82-13 x 98 ng ml(-1) in 48 h. CONCLUSION: Phenotypic and phylogenetic characteristics indicated that all isolates previously classified as Bacteroides type A strains belong to C. someare. SIGNIFICANCE AND IMPACT OF THE STUDY: This study provided the important finding of novel niche of vancomycin-resistant bacteria such as C. somerae in the intestinal tract of freshwater fish.     

Identification of QTLs for resistance to powdery mildew and SSR markers diagnostic for powdery mildew resistance genes in melon (Cucumis melo L.)

Powdery mildew caused by Podosphaera xanthii is an important foliar disease in melon. To find molecular markers for marker-assisted selection, we constructed a genetic linkage map of melon based on a population of 93 recombinant inbred lines derived from crosses between highly resistant AR 5 and susceptible ‘Earl’s Favourite (Harukei 3)’. The map spans 877 cM and consists of 167 markers, comprising 157 simple sequence repeats (SSRs), 7 sequence characterized amplified region/cleavage amplified polymorphic sequence markers and 3 phenotypic markers segregating into 20 linkage groups. Among them, 37 SSRs and 6 other markers were common to previous maps. Quantitative trait locus (QTL) analysis identified two loci for resistance to powdery mildew. The effects of these QTLs varied depending on strain and plant stage. The percentage of phenotypic variance explained for resistance to the pxA strain was similar between QTLs (R ² = 22–28%). For resistance to pxB strain, the QTL on linkage group (LG) XII was responsible for much more of the variance (41–46%) than that on LG IIA (12–13%). The QTL on LG IIA was located between two SSR markers. Using an independent population, we demonstrated the effectiveness of these markers. This is the first report of universal and effective markers linked to a gene for powdery mildew resistance in melon.     

The use of poly-L-lysine to facilitate examination of sperm entry into pelagic, non-adhesive fish eggs

The fish egg is surrounded by a thick envelope called the chorion. The fertilizing spermatozoon enters the egg through a canal-like structure in the chorion, the micropyle. Examination of micropyle at fertilization is difficult if eggs are large and have no distinct landmarks surrounding the micropyle, or if they are positively buoyant in water. Eggs of many commercially important fishes (e.g., flounder, sea bream and eel) are buoyant in water or only slightly adhere to solid objects (e.g., sands, rock and water plants), which makes observation of spermatozoa at fertilization difficult. Here, we report that such eggs can be firmly attached to plastic and glass dishes that have been previously coated with poly-L-lysine. These adhering eggs can be fertilized and develop normally on the dishes. Observations of micropyles of three fish species, before and after sperm entry are presented.     

Detailed analysis of formation of chicken pituitary primordium in early embryonic development

The primordium of the mammalian adenohypophysis derived from Rathke's pouch (RP) is known to be formed by oral ectoderm invagination. However, in the early phase of pituitary development, the detailed process by which the oral ectoderm develops into the adenohypophysis remains largely unknown. Using high-resolution non-radiolabeled in situ hybridization and the BrdU and TUNEL methods, we have examined the detailed expression pattern of factors involved in the formation of RP of chicken and the changes in the mitotic and apoptotic cell regions in RP. In the chicken embryo, Sonic hedgehog (Shh) mRNA was initially expressed in the stomodeal plate but not in the oral ectoderm. After prospective diencephalon had detached from the oral ectoderm, another Shh-expressing region appeared in the most rostral part of the recess. LIM homeobox gene 3 (Lhx3) mRNA first appeared in the anterior area of Rathke's recess, and expression then spread to the caudal region. alphaGSU mRNA-expressing cells were observed at both ends of the Lhx3-expressing region, and thereafter the expression area moved to the posterior region. Furthermore, a close overlap was found between the proliferating region and Lhx3 mRNA-expressing area, and TUNEL-positive cells appeared in Seessel's pouch derived from the foregut. Thus, the primordium of the pituitary gland corresponding to the Lhx3-expressing region is surrounded by the Shh-expressing region, which appears in two steps, and the mass growth and invagination of RP of chicken result from the coordination of the dorsal extension of the anterior region and the ventral extension of the posterior region of RP.     

Unique ethylene-regulated touch responses of Arabidopsis thaliana roots to physical hardness

Although touch responses of plant roots are an important adaptive behavior, the molecular mechanism remains unclear. We have developed a bioassay for measuring root-bending responses to physical hardness in Arabidopsis thaliana seedlings. Our test requires a two-layer solid medium. Primary roots growing downward through an upper layer of 0.3% phytagel either penetrate the lower layer or bend along an interface between the upper and lower layers with different concentrations (0.2–0.5%, corresponding to 1.57–6.79 gw mm⁻² in hardness). In proportion to increasing hardness of the lower layer, we found that the percentage of bending roots increased and ethylene production decreased, suggesting an inverse relationship between the root-bending response and ethylene production. Studies with ethylene biosynthesis modulators and mutants also suggested that bending and non-bending responses of roots to medium hardness depend, respectively, on decreased and increased ethylene biosynthesis. In addition, the degrees of root-tip softening and differential root-cell growth, both possible factors determining root-bending response, were enhanced and attenuated by decreased and increased amounts of ethylene, respectively—also in bending roots and non-bending roots. Our findings indicate that ethylene regulates root touch responses, probably through a combination of root-tip softening (or hardening) and differential root-cell growth.     

Structural elucidation and synthesis of 3-hydroxybenzene-1,2-dicarbaldehyde from astigmatid mites.

The structure of a novel aromatic compound contained in the unidentified Rhizoglyhus mite (Acaridae: Astigmata) was elucidated, without its isolation, to be 3-hydroxybenzene-1,2-dicarbaldehyde (tentatively named gamma-acaridial) by a combination of GC/MS and GC/FT-IR together with knowledge of related mite compounds. The structure was confirmed by a 5-step synthesis, starting from methyl 3-hydroxybenzoate, in a 15% overall yield. The compound is widely distributed not only among Astigmata but also among Oribatida, although its biological function is obscure at present.     

Analysis of Petal Anthocyanins to Investigate Flower Coloration of Zhongyuan (Chinese) and Daikon Island (Japanese) Tree Peony Cultivars

Pn, Pg; Pn, Pg > Cy ; Pn, Cy and Pn, Cy > Pg groups. Each group consequently specified significant features among CIELAB color notation and petal pigmentation, being adequate to characterize tree peony flowers as similar between Zhongyuan and Daikon Island cultivars, thus the cultivars of the two areas are suggested to be related to one another. Received 25 April 2000/ Accepted in revised form 21 December 2000     

Protective Effect of External Ca2+ on Elongation and the Intracellular Concentration of K+ in Intact Mung Bean Roots under High NaCl Stress

The effects of Ca²⁺ in the external medium on intact mung beanroots under high NaCl stress were investigated. With increasingexternal concentrations of NaCl, mung bean roots showed suppressionof elongation and a decrease in the intracellular concentrationof K⁺. Addition of Ca²⁺ to the external medium alleviated theinhibition of root elongation under the high NaCl stress andmaintained a high intracellular concentration of K⁺ in the elongatingregion of the roots. This counter effect of Ca²⁺ against theNaCl stress on roots was correlated with the ratio of [Ca²⁺]/[Na⁺]²in the external medium. A value above 5.0 ? 10^–4 mM^–1resulted in almost complete recovery of root elongation undervarious high concentrations of NaCl. Root elongation for 24h under NaCl stress was correlated with the extent to whichthe intracellular concentration of K⁺ was in excess of 10 mM.Maintenance of an adequate concentration of K⁺ in root cellsis essential for root elongation under salt stress. These findingsindicate that Ca²⁺ prevents the leakage of intracellular K⁺and thereby supports the elongation of roots under salt stress. (Received November 13, 1989; Accepted June 5, 1990)