Dominant effects of litter substrate quality on the difference between leaf and root decomposition process above- and belowground

Initial decomposition rates, changes in organic chemical components (acid-insoluble fraction, holocellulose, polyphenols, soluble carbohydrates) and nutrient dynamics (K, Mg, Ca, P, N) were examined for fine roots and leaves of Japanese cypress (Chamaecyparis obtusa). Litterbag experiments designed to evaluate the relative effects of litter type and position of litter supply in the soil were carried out, considering that root and leaf litter typically occupy different locations and have different substrate qualities. Litterbags of roots and leaves were placed at two positions (on the soil surface and in the humus layer), and collected every 3 months over one year. The mass loss rate and N release were slower during root decomposition in the humus layer than during leaf decomposition on the soil surface. These differences between root and leaf decomposition were mainly caused by the litter type, and the effect of the position on decomposition was relatively small. Root litter was less influenced by position related effects, such as differences in humidity, than leaf litter, and this recalcitrant trait to environmental effects may be responsible for the slower mass loss rate and N release in root decomposition. The results of the present study suggest that fine roots are persistent in the soil and serve an important role in N retention in forest ecosystems because of their litter substrate quality.     

Isolation and characterization of microorganisms capable of hydrolysing the herbicide mefenacet

Three strains—Nocardioides sp. MFC-A, Rhodococcus rhodochrous MFC-B, and Stenotrophomonas sp. MFC-C—were newly isolated from rice soil or bark compost as microorganisms capable of cometabolically degrading mefenacet (2-benzothiazol-2-yloxy-N-methyl-acetanilide). Several other species belonging to the genera Nocardioides, Rhodococcus, and Stenotrophomonas were also capable of degrading mefenacet, suggesting that the ability is not specific to these isolates, but common at least in these genera. N-methylaniline and 2-benzothiazoloxy acetic acid were identified as the metabolites by liquid chromatography-mass spectrometry. Besides mefenacet, the isolates could degrade one or more other amide pesticides, such as flutolanil, mepronil, metolachlor, and pretilachlor. These results indicate that the strains Nocardioides sp. MFC-A, Rhodococcus rhodochrous MFC-B, and Stenotrophomonas sp. MFC-C degrade mefenacet via hydrolysis of the amide bond, but their substrate specificities differ.     

Expression and properties of two types of protein kinase C: alternative splicing from a single gene

Two complementary DNA's, encoding the complete sequences of 671 and 673 amino acids for subspecies of rat brain protein kinase C, were expressed in COS 7 cells. The complementary DNA sequence analysis predicted that the two enzymes are derived from different ways of splicing and differ from each other only in the short ranges of their carboxyl-terminal regions. Both enzymes showed typical characteristics of protein kinase C that responded to Ca2+, phospholipid, and diacylglycerol. The enzymes showed practically identical physical and kinetic properties and were indistinguishable from one of the several subspecies of protein kinase C that occurs in rat brain but not in untransfected COS 7 cells. Partial analysis of the genomic structure confirmed that these two subspecies of protein kinase C resulted indeed from alternative splicing of a single gene.     

Experimental dual infection of pigs with an H1N1 swine influenza virus (A/Sw/Hok/2/81) and Mycoplasma hyopneumoniae

Dual infection of pigs with swine influenza virus (SIV) and Mycoplasma hyopneumoniae was carried out to compare the clinical and pathological effects of dual infection in caesarian derived and colostrums deprived (CDCD) pigs, with that of a single infection with M. hyopneumoniae. In Experiment 1, 40-day-old CDCD pigs were inoculated only with SIV (A/Sw/Hok/2/81, H1N1). The virus was isolated from nasal swabs for 5-6 days. None of these pigs showed clinical signs of infection throughout the experimental period. These results suggested that this strain can infect pigs but is only slightly pathogenic when it is inoculated singly to a CDCD pig. In Experiment 2, 60-day-old CDCD pigs were inoculated with M. hyopneumoniae and then were inoculated with SIV (A/Sw/Hok/2/81) at 1 week (MHYO-7d-SIV-7d group) or 3 weeks (MHYO-21d-SIV-7d group) after M. hyopneumoniae inoculation. Macroscopically, dark red-to-purple lung lesions were observed in all of pigs at 14 or 28 days post-inoculation. Percentages of dark red-to-purple lung lesions in dual infection groups (MHYO-7d-SIV-7d group: 18.7 +/- 4.2%, MHYO-21d-SIV-7d group: 23.0 +/- 8.0%) were significantly (P < 0.05) increased compared to those of each control group in which pigs were inoculated only with M. hyopneumoniae (MHYO-14d group: 4.7 +/- 2.9%, MHYO-28 group: 3.3 +/- 2.4%). Microscopically, bronchial epithelial lesions (epithelial disruption, degeneration, hyperplasia and formation of microabscess) were frequently observed in dark red-to-purple lung lesions of only the dual infection groups. These results demonstrate that the lung lesion of pigs inoculated with M. hyopneumoniae and SIV is more severe than that of pigs inoculated only with M. hyopneumoniae.     

Primary cardiac fibrosarcoma in a dog

A primary cardiac fibrosarcoma in the right atrium of a 6-year-old Chihuahua dog is described. At necropsy, there was a firm, whitish and spherical mass in the right atrium. Histopathologically, the mass had moderate cellularity composed of spindle-shaped cells with scattered multinucleated giant cells. The tumor cells were arranged in interwoven bundles and sheets in the collagenous stroma. No metastases were observed. Ultrastructurally, the tumor cells mainly consisted of fibroblasts. Multinucleated giant cells did not have any certain organelles that would indicate a higher order of differentiation. Primary cardiac sarcomas in dogs are extremely rare.     

Population size and specific nitrification potential of soil ammonia-oxidizing bacteria under long-term fertilizer management

Population size of soil ammonia-oxidizing bacteria (AOB) was quantified by real-time PCR in a long-term (16 years) field experiment under different fertilizer managements. AOB population sizes in mineral nitrogen-fertilized soils and organic manure-fertilized soil were 10.3 and 3.1 times, respectively, that of the control, while phosphorus and potassium fertilization had no significant effect. On the other hand, the AOB specific nitrification potential (soil nitrification potential per AOB cell) was significantly higher (P < 0.05) in organic manure-fertilized soil than in mineral-fertilized soils and the control, indicating that AOB was likely more metabolically active in organic manure-fertilized soils than in mineral nitrogen-fertilized soils after long-term application.     

Contributions of the lipopolysaccharide outer core oligosaccharide region on the cell surface properties of Pseudomonas aeruginosa

We have characterized the cell surface properties of three mutant series of Pseudomonas aeruginosa that show various defects in their lipopolysaccharide (LPS) core region. The deepest rough mutants of each series used in this study lacked completely rhamnose and glucose, and contained only galactosamine and alanine as LPS outer core constituents. However, rough mutants other than the deepest rough mutants showed high cell surface hydrophobicity compared to the corresponding parental strains, the deepest rough mutants showed less hydrophobicity than other rough mutants. The reactivity of an anti-lipid A monoclonal antibody with the deepest rough mutants was markedly higher than that with other counterparts. The deepest rough mutants tended to be more susceptible to antibiotics, such as gentamicin and polymyxin B, than the corresponding parental strains and other rough mutants. The above evidence indicates that neutral sugar, namely rhamnose and glucose, residues of the LPS outer core region play a critical role in the cell surface properties of P. aeruginosa.