Physiological Characterization of an Anaerobic Ammonium-Oxidizing Bacterium Belonging to the “Candidatus Scalindua” Group

The phylogenetic affiliation and physiological characteristics (e.g., K_s and maximum specific growth rate [μ_max]) of an anaerobic ammonium oxidation (anammox) bacterium, “Candidatus Scalindua sp.,” enriched from the marine sediment of Hiroshima Bay, Japan, were investigated. “Candidatus Scalindua sp.” exhibits higher affinity for nitrite and a lower growth rate and yield than the known anammox species.     

Exploring the effects of immunity and life history on the dynamics of an endogenous retrovirus

Mammalian DNA is littered with the signatures of past retroviral infections. For example, at least 8% of the human genome can be attributed to endogenous retroviruses (ERVs). We take a single-locus approach to develop a simple susceptible–infected–recovered model to investigate the circumstances under which a disease-causing retrovirus can become incorporated into the host genome and spread through the host population if it were to confer an immunological advantage. In the absence of any fitness benefit provided by the long terminal repeat (LTR), we conclude that signatures of ERVs are likely to go to fixation within a population when the probability of evolving cellular/humoral immunity to a related exogenous version of the virus is extremely small. We extend this model to examine whether changing the speed of the host life history influences the likelihood that an exogenous retrovirus will incorporate and spread to fixation. Our results reveal the parameter space under which incorporation of exogenous retroviruses into a host genome may be beneficial to the host. In our final model, we find that the likelihood of an LTR reaching fixation in a host population is not strongly affected by host life history.     

The First and Second Dissociation Constants of Subtilisin BPN′-Plasminostreptin Complex Determined by a Polarographic Method,and the Effects of pH on Them

A polarographic method based on the Brdi?ka current (the polarographic catalytic hydrogen evolution current produced by proteins in the presence of cobalt salts) was applied to direct titration of subtilisin BPN′ (S.BPIST) with plasminostreptin (PS) at a concentration level of 10”⁸ m. The first and second dissociation constants of the S.BPN-PS complex were determined by fitting theoretical curves to the titration data, in which the multiple equilibria involving microscopically distinct forms of S.BPN-PS complex were taken into account. The intrinsic free energy change in the first binding of S.BPN′ to dimeric PS was larger than that in the second binding. The dependence of the microscopic dissociation constants of S.BPN′-PS complex on pH indicates the participation of ionizable groups of pK_a 8.0 and 9.4 in the complex formation. The repulsive effect between negatively charged molecules of S.BPN′ and PS in the complex formation at elevated pH is suggested.     

Metabolic stability and inhibitory effect of O-methylated theaflavins on H2O2-induced oxidative damage in human HepG2 cells

Seven new O-methylated theaflavins (TFs) were synthesized by using O-methyltransferase from an edible mushroom. Using TFs and O-methylated TFs, metabolic stability in pooled human liver S9 fractions and inhibitory effect on H₂O₂-induced oxidative damage in human HepG2 cells were investigated. In O-methylation of theaflavin 3′-O-gallate (TF3′G), metabolic stability was potentiated by an increase in the number of introduced methyl groups. O-methylation of TF3,3′G did not affect metabolic stability, which was likely because of a remaining 3-O-galloyl group. The inhibitory effect on oxidative damage was assessed by measuring the viability of H₂O₂-damaged HepG2 cells treated with TFs and O-methylated TFs. TF3,3′G and O-methylated TFs increased cell viabilities significantly compared with DMSO, which was the compound vehicle (p?<?0.05), and improved to approximately 100%. Only TF3′G did not significantly increase cell viability. It was suggested that the inhibitory effect on H₂O₂-induced oxidative damage was potentiated by O-methylation or O-galloylation of TFs.     

Innate immune cells are dispensable for regenerative growth of imaginal discs

Following tissue damage the immune response, including inflammation, has been considered an inevitable condition to build the host defense against invading pathogens. The recruitment of innate immune leukocytes to injured tissue is observed in both vertebrates and invertebrates. However, it is still not conclusive whether the inflammatory response is also indispensable for the wound healing process by itself, in addition to its role in microbial clearance. In this study we determine the requirement of innate immune cells, both hemocytes and fat body cells, in Drosophila imaginal disc regeneration. We investigate wound healing and regenerative cell proliferation of damaged imaginal discs under immunodeficient conditions. To delay development of Drosophila at matured third instar larval stage we used a sterol-mutant erg2 knock-out yeast strain in the medium. This dietary-controlled developmental arrest allowed us to generate larvae free of immune cells without interfering with their larval development. In addition, this approach allowed uncoupling regenerative cell proliferation of damaged discs from their normal developmental growth. We furthermore examined the regenerative cell proliferation of fragmented imaginal discs by transplantation into host flies deficient of immune cells. We demonstrate that the damaged/fragmented discs in immune cells deficient conditions still exhibit regenerative cell proliferation comparable to those of control samples. These results suggest that recruitment of immune cells is not a prerequisite for the regenerative growth of damaged imaginal discs.     

Population genetic structure of Bryde’s whales (<Emphasis Type="Italic">Balaenoptera brydei</Emphasis>) at the inter-oceanic and trans-equatorial levels

Bryde’s whales (Balaenoptera brydei) differ from other typical baleen whale species because they are restricted to tropical and warm temperate waters in major oceans, and frequent trans-equatorial movement has been suggested for the species. We tested this hypothesis by analyzing genetic variation at 17 microsatellite loci (N = 508) and 299 bp of mitochondrial DNA (mtDNA) control region sequences (N = 472) in individuals obtained from the western North Pacific, South Pacific, and eastern Indian Ocean. Combined use of microsatellite and mtDNA markers allowed us to distinguish between contemporary gene flow and ancestral polymorphism and to describe sex-specific philopatry. A high level of genetic diversity was found within the samples. Both nuclear and mtDNA markers displayed similar population structure, indicating a lack of sex-specific philopatry. Spatial structuring was detected using both frequency-based population parameters and individual-based Bayesian approaches. Whales in the samples from different oceanic regions came from genetically distinct populations with evidence of limited gene flow. We observed low mtDNA sequence divergence among populations and a lack of concordance between geographic and phylogenetic position of mtDNA haplotypes, suggesting recent separation of populations rather than frequent trans-equatorial and inter-oceanic movement. We conclude that current gene flow between Bryde’s whale populations is low and that effective management actions should treat them as separate entities to ensure continued existence of the species.