Mode of Bactericidal Action of Silver Zeolite and Its Comparison with That of Silver Nitrate

The properties of the bactericidal action of silver zeolite as affected by inorganic salts and ion chelators were similar to those of silver nitrate. The results suggest that the contact of the bacterial cell with silver zeolite, the consequent transfer of silver ion to the cell, and the generation of reactive oxygen species in the cell are involved in the bactericidal activity of silver zeolite.     

Protection against influenza virus infection in polymeric Ig receptor knockout mice immunized intranasally with adjuvant-combined vaccines

The role of secretory IgA in conferring cross-protective immunity was examined in polymeric (p)IgR knockout (KO) mice immunized intranasally with different inactivated vaccines prepared from A/PR/8/34 (H1N1), A/Yamagata/120/86 (H1N1), A/Beijing/262/95 (H1N1), and B/Ibaraki/2/85 viruses and infected with the A/PR/8/34 virus in the upper respiratory tract (RT)-restricting volume. In wild-type mice, immunization with A/PR/8/34 or its variant (A/Yamagata/120/86 and A/Beijing/262/95) vaccines conferred complete protection or partial cross-protection against infection, while the B-type virus vaccine failed to provide protection. The protection or cross-protection was accompanied by an increase in the nasal A/PR/8/34 hemagglutinin-reactive IgA concentration, which was estimated to be >30 times the serum IgA concentration and much higher than the nasal IgG concentration. In contrast, the blockade of transepithelial transport of dimeric IgA in pIgR-KO mice reduced the degree of protection or cross-protection, in parallel with the marked increase in serum IgA concentration and the decrease in nasal IgA concentration (about 20 and 0.3 times those in wild-type mice, respectively). The degree of the reduction of protection or cross-protection was moderately reversed by the low but non-negligible level of nasal IgA, transudates from the accumulated serum IgA. These results, together with the absence of the IgA-dependent cross-protection in the lower RT and the unaltered level of nasal or serum IgG in wild-type and pIgR-KO mice, confirm that the actively secreted IgA plays an important role in cross-protection against variant virus infection in the upper RT, which cannot be substituted by serum IgG.     

Dimethyl sulfoxide-induced high enantioselectivity of subtilisin Carlsberg for hydrolysis of ethyl 2-(4-substituted phenoxy)propionates

The enantioselectivity for subtilisin-catalyzed hydrolysis of ethyl 2-(4-substituted phenoxy)propionates in an aqueous buffer solution was improved by addition of DMSO (54–56% v/v). On the basis of the conformational change of subtilisin Carlsberg observed for FT-IR and CD spectra, the high enantioselectivity for subtilisin-catalyzed hydrolysis of racemic ethyl 2-(4-ethylphenoxy)propionate could be related to a partial decrease of the tertiary structure of the enzyme protein arising from an increase of the ratio of DMSO in the reaction medium. This mechanistic model for the enantiorecognition can also be supported by the discussion based on the value of the Michaelis constant (K _m) obtained for each enantiomer of the substrate.     

Localization of fluorescent substances in the cellular slime moldDictyostelium discoideum cells during growth and development

The localization of fluorescent substance was observed microscopically in livingDictyostelium discoideum cells. The fluorescence was localized in the vacuoles of the vegetative cells. The fluorescent vacuoles were not observed in the dead cells. The fluorescent vacuoles in the cytoplasm were lost in starved cells which are able to form an aggregate and to differentiate. The fluorescent vacuoles were not lost but decreased slightly in the cytoplasm of full grown cells and of cells grown in liquid nutrient medium for an extended period of time (stationary phase cells). On a solid substratum, fluorescent vacuoles were also lost from the cells, where the vegetative cells aggregate and form a slug-shaped mass of cells. The whole slug showed homogeneous fluorescence. In a finally constructed fruiting body, the spore mass showed fluorescence. In a spore mass, the fluorescence was not observed in the spores but in the interspore space of the spore mass. It is suggested that vegetative cells secrete fluorescent substance into the inter-cellular space in the mass of cells during development.     

Gain and loss of an intron in a protein-coding gene in Archaea: the case of an archaeal RNA pseudouridine synthase gene

Background  

We previously found the first examples of splicing of archaeal pre-mRNAs for homologs of the eukaryotic CBF5 protein (also known as dyskerin in humans) in Aeropyrum pernix, Sulfolobus solfataricus, S. tokodaii, and S. acidocaldarirus, and also showed that crenarchaeal species in orders Desulfurococcales and Sulfolobales, except for Hyperthermus butylicus, Pyrodictium occultum, Pyrolobus fumarii, and Ignicoccus islandicus, contain the (putative) cbf5 intron. However, the exact timing of the intron insertion was not determined and verification of the putative secondary loss of the intron in some lineages was not performed.     

Toxicity of the aphid Aulacorthum magnoliae to the predator Harmonia axyridis (Coleoptera: Coccinellidae) and genetic variance in the assimilation of the toxic aphids in H. axyridis larvae

Larvae of the ladybird Harmonia axyridis are reported to suffer high mortality when they are fed with the aphid Aulacorthum magnoliae associated with the elder Sambucus sieboldiana. In the present study we first examined whether aphid toxicity to H. axyridis was altered when the aphids were reared on different host plants, and second whether some ladybird families could adapt specially to the toxic aphids. Ladybird larvae from each egg batch were divided into two groups; one group was fed with A. magnoliae reared on potato, and the other group was fed with A. magnoliae reared on elder. The ladybird larvae fed with elder aphids suffered significantly higher mortality and grew more slowly than did larvae fed with potato aphids. This result indicates that A. magnoliae aphids absorbed toxic substances or their precursors from S. sieboldiana. We suggest that host association of A. magnoliae with the primary host plant S. sieboldiana has been maintained because of the advantage of deterring predation. Significant and positive correlation was detected across H. axyridis sib families between the mean weight of larvae fed with elder aphids and the mean weight of larvae fed with potato aphids. The hypothesis that some ladybird families adapt specially to the toxic aphids was not supported. However, the available evidence showed that a large amount of genetic variance in performance is maintained in a wild population of the ladybird H. axyridis.     

Detection of marine birnavirus in the Japanese pearl oyster Pinctada fucata and seawater from different depths

This study examines the seasonal changes of marine birnavirus (MABV) in seawater and the Japanese pearl oyster Pinctada fucata reared at different depths (2 and 15 m). Oysters and seawater were collected in 1998, and a 2-step PCR was carried out to detect MABV. Virus isolation was performed on the PCR-positive samples in the oyster. The detection rate of the MABV genome in the oyster was low during June, but increased after July at both 2 and 15 m depths. MABV was not isolated until after September, when isolation rates of 10 to 28.6% were recorded. The results suggest that growth of MABV in the oyster is similar at 2 and 15 m depth. In contrast, the MABV genome in seawater was present through the year at 15 m depth, but was not detected in summer at 2 m. This suggests that the virus is destroyed by UV and/or other factors at 2 m in summer, but is stable in deeper waters.     

Genome-resolved viral and cellular metagenomes revealed potential key virus-host interactions in a deep freshwater lake

Metagenomics has dramatically expanded the known virosphere, but freshwater viral diversity and their ecological interaction with hosts remain poorly understood. Here, we conducted a metagenomic exploration of planktonic dsDNA prokaryotic viruses by sequencing both virion (<0.22 μm) and cellular (0.22–5.0 μm) fractions collected spatiotemporally from a deep freshwater lake (Lake Biwa, Japan). This simultaneously reconstructed 183 complete (i.e., circular) viral genomes and 57 bacterioplankton metagenome-assembled genomes. Analysis of metagenomic read coverage revealed vertical partitioning of the viral community analogous to the vertically stratified bacterioplankton community. The hypolimnetic community was generally stable during stratification, but occasionally shifted abruptly, presumably due to lysogenic induction. Genes involved in assimilatory sulfate reduction were encoded in 20 (10.9%) viral genomes, including those of dominant viruses, and may aid viral propagation in sulfur-limited freshwater systems. Hosts were predicted for 40 (21.9%) viral genomes, encompassing 10 phyla (or classes of Proteobacteria) including ubiquitous freshwater bacterioplankton lineages (e.g., Ca. Fonsibacter and Ca. Nitrosoarchaeum). Comparison with viral genomes derived from published metagenomes revealed viral phylogeographic connectivity in geographically isolated habitats. Notably, analogous to their hosts, actinobacterial viruses were among the most diverse, ubiquitous and abundant viral groups in freshwater systems, with potential high lytic activity in surface waters.     

Feeding stimulant in Cinnamomum camphora for the common bluebottle, Graphium sarpedon nipponum (Lepidoptera: Papilionidae)

The acceptance of camphor tree (Cinnamomum camphora) as a host plant for the larvae of common bluebottle (Graphium sarpedon nipponum) was explained by the presence of feeding stimulants in the leaves. When the active methanol extract of C. camphora leaves was separated into hexane and water layers, both layers showed high feeding activities for the larvae of G. sarpedon nipponum. Bioassay-guided fractionation of the hexane layer resulted in the isolation of a highly active compound, which was identified as a-linolenic acid by nuclear magnetic resonance spectrometry and gas chromatography-mass spectrometry.