Vitamin C Maintenance against Cell Growth Arrest and Reactive Oxygen Species Accumulation in the Presence of Redox Molecular Chaperone hslO Gene.

Chromosome damage combined with defective recombinase activity renders cells inviable, owing to deficient double-strand break repair. Despite this, recA polA cells grow well under either DNA damage response (SOS) conditions or catalase medium supplementation. Catalase treatments reduce intracellular reactive oxygen species (ROS) levels, suggesting that recA polA cells are susceptible to not only chronic chromosome damage but also ROS. In this study, we used a reducing agent, vitamin C, to confirm whether cell growth could be improved. Vitamin C reduced ROS levels and rescued colony formation in recAts polA cells under restrictive temperatures in the presence of hslO, the gene encoding a redox molecular chaperone. Subsequently, we investigated the role of hslO in the cell growth failure of recAts polA cells. The effects of vitamin C were observed in hslO+ cells; simultaneously, cells converged along several ploidies likely through a completion of replication, with the addition of vitamin C at restrictive temperatures. These results suggest that HslO could manage oxidative stress to an acceptable level, allowing for cell division as well as rescuing cell growth. Overall, ROS may regulate several processes, from damage response to cell division. Our results provide a basis for understanding the unsolved regulatory interplay of cellular processes.

Reactive oxygen species accumulation is synchronised with growth inhibition of temperature-sensitive recAts polA Escherichia coli.

When combined with recombinase defects, chromosome breakage and double-strand break repair deficiencies render cells inviable. However, cells are viable when an SOS response occurs in recAts polA cells in Escherichia coli. Here, we aimed to elucidate the underlying mechanisms of this process. Transposon mutagenesis revealed that the hslO gene, a redox chaperone Hsp33 involved in reactive oxidative species (ROS) metabolism, was required for the suppression of recAts polA lethality at a restricted temperature. Recently, it has been reported that lethal treatments trigger ROS accumulation. We also found that recAts polA cells accumulated ROS at the restricted temperature. A catalase addition to the medium alleviates the temperature sensitivity of recAts polA cells and decreases ROS accumulation. These results suggest that the SOS response and hslO manage oxidative insult to an acceptable level in cells with oxidative damage and rescue cell growth. Overall, ROS might regulate several cellular processes.

Vegetative and reproductive growth of Arabidopsis under microgravity conditions in space.

We have performed a seed-to-seed experiment in the cell biology experiment facility (CBEF) installed in the Kibo (Japanese Experiment Module) in the International Space Station. The CBEF has a 1 × g compartment on a centrifuge and a microgravity compartment, to investigate the effects of microgravity on the vegetative and reproductive growth of Arabidopsis thaliana (L.) Heynh. Seeds germinated irrespective of gravitational conditions after water supply on board. Thereafter, seedlings developed rosette leaves. The time of bolting was slightly earlier under microgravity than under space 1 × g. Microgravity enhanced the growth rate of peduncles as compared with space 1 × g or ground control. Plants developed flowers, siliques and seeds, completing their entire life cycle during 62-days cultivation. Although the flowering time was not significantly affected under microgravity, the number of flowers in a bolted plant significantly increased under microgravity as compared with space 1 × g or ground control. Microscopic analysis of reproductive organs revealed that the longitudinal length of anthers was significantly shorter under microgravity when compared with space 1 × g, while the length of pistils and filaments was not influenced by the gravitational conditions. Seed mass significantly increased under microgravity when compared with space 1 × g. In addition, seeds produced in space were found not to germinate on the ground. These results indicate that microgravity significantly influenced the reproductive development of Arabidopsis plants even though Earth's gravitational environment is not absolutely necessary for them to complete their life cycle.

Alteromonas gracilis sp. nov., a marine polysaccharide-producing bacterium.

A novel exopolysaccharide-producing bacterium, designated strain 9a2(T), was isolated from Pacific Ocean sediment. The strain was Gram-stain-negative, motile, strictly aerobic, oxidase- and catalase-positive, and required NaCl for growth. Its major isoprenoid quinone was ubiquinone-8 (Q-8), and its cellular fatty acid profile consisted mainly of C16 : 1ω7c, C18 : 1ω9c and C16 : 0. The DNA G+C content was 46.6 mol%. 16S rRNA gene sequence analysis suggested that strain 9a2(T) is a member of the genus Alteromonas . Strain 9a2(T) exhibited closest phylogenetic affinity to Alteromonas macleodii NBRC 102226(T) (99.3% 16S rRNA gene sequence similarity), A. marina SW-47(T) (99.3%), A. litorea TF-22(T) (99.0%), A. australica H17(T) (98.7%), A. simiduii BCRC 17572(T) (98.5%), A. stellipolaris LMG 21861(T) (98.3%) and A. hispanica F-32(T) (98.2%). The DNA-DNA reassociation values between strain 9a2(T) and A. macleodii JCM 20772(T), A. marina JCM 11804(T), A. litorea JCM 12188(T), A. australica CIP 109921(T), A. simiduii JCM 13896(T), A. stellipolaris LMG 21861(T) and A. hispanica LMG 22958(T) were below 70%. Strain 9a2(T) contained phosphatidylethanolamine, phosphatidylglycerol and an unidentified polar lipid. Owing to differences in phenotypic and chemotaxonomic characteristics, phylogenetic analysis based on 16S rRNA gene sequences and DNA-DNA relatedness data, the isolate merits classification as representing a novel species, for which the name Alteromonas gracilis sp. nov. is proposed. The type strain of this species is 9a2(T) ( =JCM 30236(T) =NCIMB 14947(T)).

Psychrobacter oceani sp. nov., isolated from marine sediment.

A novel marine bacterium, designated strain 4k5(T), was isolated from a sediment sample of the Pacific Ocean. The strain was Gram-stain-negative, strictly aerobic, non-motile, oxidase-positive and catalase-positive and required Na(+) for growth. Its major isoprenoid quinone was ubiquinone 8 (Q-8), and its cellular fatty acid profile consisted mainly of C18 : 1v9c (71.4%), C16 : 1v7c (9.1%) and C18 : 0. The DNA G+C content was 45.3 mol%. 16S rRNA gene sequence analysis suggested that strain 4k5(T) is a member of the genus Psychrobacter . Strain 4k5(T) exhibited the closely phylogenetic affinity to Psychrobacter pacificensis IFO 16270(T) (99.4% 16S rRNA gene sequence similarity), P. piscatorii T-3-2(T) (97.7%), P. nivimaris 88/2-7(T) (97.7%), P. celer SW-238(T) (97.7%), P. aestuarii SC35(T) (97.6%) and P. vallis CMS39(T) (97.6%). DNA-DNA hybridization between strain 4k5(T) and P. pacificensis NBRC 103191(T), P. piscatorii JCM 15603(T). P. nivimaris DSM 16093(T), P. celer JCM 12601(T), P. aestuarii JCM 16343(T) and P. vallis DSM 15337(T) was 42.5, 47.0, 38.1, 23.7, 9.0 and 27.4%, respectively. Owing to the significant differences in phenotypic and chemotaxonomic characteristics, phylogenetic analysis based on the 16S rRNA gene sequence and DNA-DNA relatedness data, the isolate merits classification within a novel species, for which the name Psychrobacter oceani sp. nov. is proposed. The type strain is 4k5(T) ( = JCM 30235(T) =NCIMB 14948(T)).

Pseudoalteromonas shioyasakiensis sp. nov., a marine polysaccharide-producing bacterium.

A novel exopolysaccharide-producing bacterium, designated strain SE3(T), was isolated from Pacific Ocean sediment. The strain was Gram-stain-negative, motile, strictly aerobic, oxidase-positive and catalase-positive, and required Na(+) for growth. Its major isoprenoid quinone was ubiquinone-8 (Q-8), and its cellular fatty acid profile mainly consisted of C16 : 1ω7c, C16 : 0 and C18 : 1ω7c. The DNA G+C content was 46.9 mol%. 16S rRNA gene sequence analysis suggested that strain SE3(T) is a member of the genus Pseudoalteromonas. Strain SE3(T) exhibited close phylogenetic affinity to Pseudoalteromonas arabiensis JCM 17292(T) (99.0 % 16S rRNA gene sequence similarity), Pseudoalteromonas lipolytica LMEB 39(T) (98.39 %) and Pseudoalteromonas donghaensis HJ51(T) (97.65 %). The DNA-DNA reassociation values between strain SE3(T) and P. arabiensis JCM 17292(T), P. lipolytica JCM 15903(T) and P. donghaensis LMG 24469(T) were 31, 26 and 44 %, respectively. Owing to the significant differences in phenotypic and chemotaxonomic characteristics, phylogenetic analysis based on 16S rRNA gene sequences and DNA-DNA relatedness data, the new isolate merits classification as a representative of novel species, for which the name Pseudoalteromonas shioyasakiensis is proposed. The type strain is SE3(T) ( = JCM 18891(T) = NCIMB 14852(T)).

Pseudoalteromonas arabiensis sp. nov., a marine polysaccharide-producing bacterium.

A novel exopolysaccharide-producing bacterium, designated strain k53(T), was isolated from sediment from the Arabia Sea, Indian Ocean. The strain was Gram-negative, motile, strictly aerobic, oxidase-positive and catalase-positive, and required Na(+) for growth. Its major isoprenoid quinone was ubiquinone-8 (Q-8), and its cellular fatty acid profile mainly consisted of C16 : 1ω7c, C16 : 0 and C18 : 1ω7c. The DNA G+C content was 43 mol%. 16S rRNA gene sequence analysis suggested that strain k53(T) is a member of the genus Pseudoalteromonas. Strain k53(T) exhibited close phylogenetic affinity to Pseudoalteromonas lipolytica LMEB 39(T) (98.0% 16S rRNA gene sequence similarity) and Pseudoalteromonas donghaensis HJ51(T) (97.3 %).The DNA-DNA reassociation values between strain k53(T) and P. lipolytica JCM 15903(T) and P. donghaensis LMG 24469(T) were 17 % and 12 %, respectively. Owing to the significant differences in phenotypic and chemotaxonomic characteristics, and phylogenetic analysis based on the 16S rRNA gene sequence and DNA-DNA relatedness data, the isolate merits classification as a representative of a novel species, for which the name Pseudoalteromonas arabiensis is proposed. The type strain of this species is k53(T) ( = JCM 17292(T) = NCIMB 14688(T)).

Effects of ultraviolet-B irradiation on the cuticular wax of cucumber (Cucumis sativus) cotyledons.

Cucumber seedlings were grown under three doses of supplemental ultraviolet-B (UV-B) irradiation to examine the effects on the surface structure of the cotyledons. Medium and high doses of irradiation induced glazing (formation of translucent, glossy layers) on the adaxial surfaces of cotyledons, especially those exposed to a high dose of UV-B. Observation with a scanning electron microscope revealed that the adaxial surfaces of cotyledons exposed to a medium dose of UV-B and controls became rough in appearance, but unevenness of the surface was not apparent in cotyledons irradiated with a high dose of UV-B. UV-B irradiation affected the types and amounts of alkanes and primary alcohols, the main components of cucumber cuticular wax. Based on cotyledon area, the amounts of these components were significantly higher in cotyledons irradiated with a medium dose of UV-B than in controls. This effect could be a consequence of small cotyledon area and constant wax production in the cotyledons irradiated with a medium dose of UV-B. The distribution patterns of homologs within the alkane and primary alcohol fractions shifted during growth to longer alkyl chain length in the control cotyledons. UV-B irradiation repressed these changes, suggesting that UV-B acts on cuticular wax biosynthetic pathways.

Glaciecola chathamensis sp. nov., a novel marine polysaccharide-producing bacterium.

Two novel exopolysaccharide-producing bacteria, strains S18K6(T) and S18K5, were isolated from Pacific Ocean sediment. The isolates were Gram-negative, motile, strictly aerobic chemoheterotrophic bacteria. The DNA G+C contents of strains S18K6(T) and S18K5 were 44.8 and 46.3 mol%, respectively. DNA-DNA relatedness between the two strains was 70 %. Major fatty acids were hexadecanoic acid (C(16 : 0)), hexadecenoic acid (C(16 : 1)omega7c) and octadecenoic acid (C(18 : 1)omega7c). 16S rRNA gene sequence, chemotaxonomic and morphological data indicated that these strains clearly belonged to the genus Glaciecola. Based on phenotypic properties and DNA-DNA hybridization data, strains S18K6(T) and S18K5 are considered to represent a novel species of the genus Glaciecola, for which the name Glaciecola chathamensis sp. nov. is proposed. The type strain is S18K6(T) (=JCM 13645(T)=NCIMB 14146(T)).

Optical microscopy of Arabidopsis seedlings fixed in non-fresh FAA using Kennedy Fixation Tubes.

Samples will be kept in non-fresh fixative for longer period than usual in Kennedy Space Center Fixation Tubes (KFT) when they will be fixed for microscopy in the International Space Station (ISS). It is necessary to examine characteristics of samples prepared under such conditions and to improve preservation of the samples. In this study, morphology of Arabidopsis tissues prepared under such conditions was examined under a light microscope. Deformation of cell shape was observed in tissues with well-developed intercellular spaces when they were fixed in non-fresh fixative for longer period in KFTs.