Distributions of biogeochemical parameters in the pool and interstitial waters in sand bar system of the Kizu River

Distributions of biogeochemical parameters in temporary pools (TAMARI), riparian side arm of river (WANDO) and interstitial waters were investigated in the sand bars along the lower reaches of the Kizu River. Dissloved inorganic nitrogen (DIN) and phosphate (DIP) concentrations in TAMARI and WANDO waters varied greatly compared with those in river waters. Low concentrations of DIN and DIP were often observed simultaneously in TAMARI waters. The DIN concentrations of most intersitial waters were similar or high in comparison to those of river waters. Low concentrations of DIN and DIP were often observed separately in intersitial waters. Concentrations of biogeochemical constituents clearly varied greatly in the waters of sand bar systems, and the relationships between each biogeochemical constituents were different between surface water (TAMARI and WANDO) and subsurface (intersitial) waters of the Kizu River.Article信州大学山地水環境教育研究センター研究報告 2: 63-67(2004)departmental bulletin pape

Male-killing symbiont damages host's dosage-compensated sex chromosome to induce embryonic apoptosis

Some symbiotic bacteria are capable of interfering with host reproduction in selfish ways. How such bacteria can manipulate host's sex-related mechanisms is of fundamental interest encompassing cell, developmental and evolutionary biology. Here, we uncover the molecular and cellular mechanisms underlying Spiroplasma-induced embryonic male lethality in Drosophila melanogaster. Transcriptomic analysis reveals that many genes related to DNA damage and apoptosis are up-regulated specifically in infected male embryos. Detailed genetic and cytological analyses demonstrate that male-killing Spiroplasma causes DNA damage on the male X chromosome interacting with the male-specific lethal (MSL) complex. The damaged male X chromosome exhibits a chromatin bridge during mitosis, and bridge breakage triggers sex-specific abnormal apoptosis via p53-dependent pathways. Notably, the MSL complex is not only necessary but also sufficient for this cytotoxic process. These results highlight symbiont's sophisticated strategy to target host's sex chromosome and recruit host's molecular cascades toward massive apoptosis in a sex-specific manner

Basic limnological study in an alpine Lake Puma Yumco, the pre-Himalayas, China

Lake Puma Yumco is a typical alpine lake (altitude; 5,030m) located in the pre-Himalayas of Tibet, China. This study was the first limnologicak investigation. Puma Yumco (28°34'N,90°24'E) has the following morphometric properties: maximum length of 31 km; maximum width of 14 km; mean width of 9 km; shoreline of 90 km; surface area of 280 km²; shoreline development of 1.5. Transparency was approximately 10 m. Dissolved oxygen was l7 mg O₂ L⁻¹ and showed saturated values. Saljnity was 360 mg L⁻¹. The chemical type of the lake water was Mg-Ca-HCO₃-SO₄. Total nitrogenous nutrients and phosphate were extremely low at 1μM and 0.02 μM, respetively. Chlorophyll-a concentration was 0.2 mg chl.a m⁻³. Phytoplankton and zooplankton were dominated by Aphanocapsa. and Diaptomidae. The grain size of lake sediment was that of silt in most cases.Article信州大学山地水環境教育研究センター研究報告 2: 83-90(2004)departmental bulletin pape

Variable Incidence of Spiroplasma Infections in Natural Populations of Drosophila Species

Spiroplasma is widespread as a heritable bacterial symbiont in insects and some other invertebrates, in which it sometimes acts as a male-killer and causes female-biased sex ratios in hosts. Besides Wolbachia, it is the only heritable bacterium known from Drosophila, having been found in 16 of over 200 Drosophila species screened, based on samples of one or few individuals per species. To assess the extent to which Spiroplasma infection varies within and among species of Drosophila, intensive sampling consisting of 50–281 individuals per species was conducted for natural populations of 19 Drosophila species. Infection rates varied among species and among populations of the same species, and 12 of 19 species tested negative for all individuals. Spiroplasma infection never was fixed, and the highest infection rates were 60% in certain populations of D. hydei and 85% in certain populations of D. mojavensis. In infected species, infection rates were similar for males and females, indicating that these Spiroplasma infections do not confer a strong male-killing effect. These findings suggest that Spiroplasma has other effects on hosts that allow it to persist, and that environmental or host variation affects transmission or persistence leading to differences among populations in infection frequencies

Polynomorphs of Japanese Alpine Plants(3)

Article環境科学年報14:35-44(1992)research repor

Insect endosymbiont proliferation is limited by lipid availability

Spiroplasma poulsonii is a maternally transmitted bacterial endosymbiont that is naturally associated with Drosophila melanogaster. S. poulsonii resides extracellularly in the hemolymph, where it must acquire metabolites to sustain proliferation. In this study, we find that Spiroplasma proliferation specifically depletes host hemolymph diacylglyceride, the major lipid class transported by the lipoprotein, Lpp. RNAi-mediated knockdown of Lpp expression, which reduces the amount of circulating lipids, inhibits Spiroplasma proliferation demonstrating that bacterial proliferation requires hemolymph-lipids. Altogether, our study shows that an insect endosymbiont acquires specific lipidic metabolites from the transport lipoproteins in the hemolymph of its host. In addition, we show that the proliferation of this endosymbiont is limited by the availability of hemolymph lipids. This feature could limit endosymbiont over-proliferation under conditions of host nutrient limitation as lipid availability is strongly influenced by the nutritional state

Temperature Affects the Tripartite Interactions between Bacteriophage WO, Wolbachia, and Cytoplasmic Incompatibility

Wolbachia infections are a model for understanding intracellular, bacterial symbioses. While the symbiosis is often studied from a binary perspective of host and bacteria, it is increasingly apparent that additional trophic levels can influence the symbiosis. For example, Wolbachia in arthropods harbor a widespread temperate bacteriophage, termed WO, that forms virions and rampantly transfers between coinfections. Here we test the hypothesis that temperatures at the extreme edges of an insect's habitable range alter bacteriophage WO inducibility and in turn, Wolbachia densities and the penetrance of cytoplasmic incompatibility. We report four key findings using the model wasp, Nasonia vitripennis: First, both cold treatment at 18 C and heat treatment at 30 C reduce Wolbachia densities by as much as 74% relative to wasps reared at 25 C. Second, in all cases where Wolbachia densities decline due to temperature changes, phage WO densities increase and inversely associate with Wolbachia densities. Heat has a marked effect on phage WO, yielding phage densities that are 552% higher than the room temperature control. Third, there is a significant affect of insect family on phage WO and endoysmbiont densities. Fourth, at extreme temperatures, there was a temperature-mediated adjustment to the density threshold at which Wolbachia cause complete cytoplasmic incompatibility. Taken together, these results demonstrate that temperature simultaneously affects phage WO densities, endosymbiont densities, and the penetrance of cytoplasmic incompatibility. While temperature shock enhances bacteriophage inducibility and the ensuing bacterial mortality in a wide range of medically and industrially-important bacteria, this is the first investigation of the associations in an obligate intracellular bacteria. Implications to a SOS global sensing feedback mechanism in Wolbachia are discussed