Introduction of an active enzyme into permeable cells of Escherichia coli: acquisition of ultraviolet light resistance by uvr mutants on introduction of T4 endonuclease V.

Summary Plasmolysed cells of Escherichia coli N212 (uvrA recA) acquired ultraviolet resistance when the cells were exposed to high concentrations of T4 endonuclease V. With increasing concentrations of T4 enzyme, survivals of plasmolysed cells after ultraviolet irradiation increased while colony-forming ability of unirradiated plasmolysed cells was not significantly affected by the enzyme treatment. Under appropriate conditions more than 200 fold increase in survivals was observed. When plasmolysed cells were treated with a pre-heated enzyme preparation or enzyme fractions derived from T4v ₁(endonuclease V-deficient mutant)-infected cells, only little or no reactivation took place.Permeabilization of cells prior to the enzyme treatment was essential for the effective reactivation. Treatment of intact cells with the T4 enzyme did not cause any reactivation. Cells treated with 20 mM EGTA or 50 mM CaCl₂ in cold were reactivated to certain extents by the enzyme, but the extents of the reactivation were far less compared to those of plasmolysed cells.Plasmolysed cells of strains carrying a mutation in one of uvrA, uvrB and uvrC genes were reactivated by introduction of T4 endonuclease V, as was the uvrA recA double mutant. UvrD mutants were also reactivated, but rather slightly. However, wild type strain as well as strains having a mutation in recA or polA gene were not reactivated. From these results it was suggested that T4 endonuclease V, taken up into permeable cells, can function in vivo to replace defective functions, which are controlled by the uvr genes. The conditions established in the present study may be used for introduction of other proteins into viable bacterial cells.     

New clade of silicified bolidophytes that belong to Triparma (Bolidophyceae,Stramenopiles)

The small phytoplankton genus Triparma belongs to the class Bolidophyceae and contains two distinct forms: silicified species and naked flagellated species (formerly Bolidomonas). Recent studies showed that four silicified species/strains (Triparma laevis f. inornata, T. laevis f. longispina, T. strigata, and T. aff. verrucosa) belong to a single clade that is paraphyletic, because it also contains an unclassified flagellated strain, and is sister to a flagellated species, T. eleuthera. In this study, we isolated and characterized two new strains of silicified species to test the phylogenetic unity of silicified bolidophytes. The isolates were identified as T. retinervis strains because they possessed fine areolation on the cell wall. 18S rDNA and rbcL phylogenetic analyses demonstrated that T. retinervis formed a new silicified clade that is sister to the flagellated species T. pacifica. This reveals that there are at least two distinct clades including both silicified and flagellated Triparma species.     

Applications of second harmonic generation (SHG)/sum-frequency generation (SFG) imaging for biophysical characterization of the plasma membrane

The plasma membrane is a lipid bilayer of < 10 nm width that separates intra- and extra-cellular environments and serves as the site of cell-cell communication, as well as communication between cells and the extracellular environment. As such, biophysical phenomena at and around the plasma membrane play key roles in determining cellular physiology and pathophysiology. Thus, the selective visualization and characterization of the plasma membrane are crucial aspects of research in wide areas of biology and medicine. However, the specific characterization of the plasma membrane has been a challenge using conventional imaging techniques, which are unable to effectively distinguish between signals arising from the plasma membrane and those from intracellular lipid structures. In this regard, interface-specific second harmonic generation (SHG) and sum-frequency generation (SFG) imaging demonstrate great potential. When combined with exogenous SHG/SFG active dyes, SHG/SFG can specifically highlight the plasma membrane as the most prominent interface associated with cells. Furthermore, SHG/SFG imaging can be readily extended to multimodal multiphoton microscopy with simultaneous occurrence of other multiphoton phenomena, including multiphoton excitation and coherent Raman scattering, which shed light on the biophysical properties of the plasma membrane from different perspectives. Here, we review traditional and current applications, as well as the prospects of long-known but unexplored SHG/SFG imaging techniques in biophysics, with special focus on their use in the biophysical characterization of the plasma membrane.     

Drosophila big brain does not act as a water channel, but mediates cell adhesion

The neurogenic gene Drosophilabig brain (bib) has a high sequence homology to aquaporin-4. However, its cellular functions in Drosophila neurogenesis have remained elusive. Here we investigated cell adhesion, and the ion and water permeability of Bib. The adhesive function was examined by a cell aggregation assay using L cells. Bib-transfected L cells formed aggregated clusters, while control-L cells remained as a single cell suspension. Ion permeation was not confirmed in L cells stably expressing Bib. When expressed in COS7 cells, Bib exhibited limited water permeability. This newly found cell adhesive function of Bib may be important for Drosophila neurogenesis.     

Xylitol Production by an Enterobacter Species

A xylose-utilizing bacterial strain was isolated from soil.

The strain, No. 553, was identified as Enterobacter liquefaciens from the result of the taxonomical studies. This bacterium grew well on D-xylose as a sole carbon source and accumulated pentitol extracellularly in shaking culture.

Pentitol produced was isolated from the culture broth and identified as xylitol.

The xylitol production reached the maximum after the cessation of the cell growth with a yield of 33.3 mg per ml in a medium containing 10% D-xylose as a sole carbon source and no significant decline of the amount of xylitol was observed through the period of the cultivation.     

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.     

Structure of the summer under fast ice microbial community near Syowa Station,eastern Antarctica

Temporal variations in the microbial community structure of plankton, which is composed of autotrophic and heterotrophic pico-, nano- and microplankton, were investigated during the austral summer of 2005/2006 under fast ice near Syowa Station, eastern Antarctica. Autotrophic algal populations were composed almost entirely of diatoms followed by phytoflagellates such as autotrophic dinoflagellates and cryptophytes. Among the microbial community, heterotrophic biomass was dominated by heterotrophic dinoflagellates and naked ciliates and finally exceeded autotrophic biomass. Qualitative microscopic analysis revealed that heterotrophic dinoflagellates were ingesting large number of diatoms. Synchronizing fluctuation of naked ciliates with phytoflagellates suggested a predator–prey relationship between them. Our results suggest that the pelagic food webs under the extensive ice-covered areas in coastal Antarctic regions are not short but complex.