Impact of gamma irradiation on the transformation efficiency for extracellular plasmid DNA

Extracellular DNA is omnipresent in aquatic environments and is thought to be a genetic material for horizontal gene transformation between microorganisms. We studied the impact of gamma irradiation on the transformation efficiency (transformants number per ng of DNA per ml) of extracellular DNA. Plasmid pEGFP as a model extracellular DNA was irradiated by gamma rays. The transformation efficiency decreased with the increase in radiation dose. A total dose of 10Gy is normally not lethal for microorganisms but certainly affects the transformation efficiency of extracellular DNA. The decrease in the efficiency would be induced by strand breaks of extracellular DNA because the yield of both single-strand breaks (SSBs) and double-strand breaks (DSBs) increased with the increase in radiation dose. The relative transformation efficiency of SSBs and DSBs to that of covalently closed circles (CCCs) was 30.3% and 0.2%, respectively. This impact on natural transformation suggests an inability of microorganisms to acquire new characteristics which should be normally acquired.     

Polychlorinated dibenzo-p-dioxins and dibenzofurans in paddy soils and river sediments in Akita, Japan

Paddy soils and sediments from the Yoneshirogawa, Omonogawa, and Koyoshigawa River Basins in Akita were analyzed for polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs). The levels and compositions in those samples including soils from non-agricultural areas (non-agricultural soils) were investigated using isomer-specific analysis to determine characteristic sources. The PCDD/PCDF compositions in the samples were compared with respect to possible sources. The PCDD/PCDF concentrations in paddy soils were much higher than those in the non-agricultural soils and much higher than those found in other parts of Japan. Although PCDD/PCDFs were ubiquitous in sediments from river sources to mouths of the respective river basins, those concentrations were much lower than those from paddy soils and non-agricultural soils, and from other parts of Japan. Comparison of PCDD/PCDF homologues and isomer compositions for samples indicated that compositions of paddy soils and sediments, except for those from river sources, had similar characteristics to PCDD/PCDFs originating from impurities in herbicides, 2,4,6-trichlorophenyl 4-nitrophenyl ether (CNP) and pentachlorophenol (PCP), and that compositions of river-source sediments and non-agricultural soils resembled those of atmospheric depositions. Results of statistical analyses suggest that PCDD/PCDF contamination of paddy soils and sediments is attributable mainly to three sources: CNP, PCP, and atmospheric deposition. Results of this study also demonstrate that CNP and PCP are not only important contaminants of local areas of Japan, but that they exist throughout Akita, in northern Japan. We therefore conclude that PCDD/PCDF pollution caused by those compounds has a widespread influence on paddy soils and river sediments in Japan.     

Cracking styrene derivative polymers in decalin solvent with metal-supported carbon catalysts

The cracking of styrene derivative polymers dissolved in decalin was conducted with metal-supported carbon catalysts under an inert gas atmosphere to recover monosubstituted styrene or monosubstituted ethylbenzene in higher yields than is obtained by pyrolysis, and to elucidate the detailed reaction mechanisms in the solvent. Poly-(4-methylstyrene), poly-(4-t-butylstyrene), poly-(α-methylstyrene), and polystyrene were used. In decalin without a catalyst, each polymer was decomposed into the monomer, dimer, and trimer derived from the corresponding polymer except for poly-(α-methylstyrene), which was decomposed into the monomer and styrene. By using metal-supported carbon, the olefinic compounds derived from the corresponding polymer were thoroughly hydrogenated to the saturated form in a nitrogen atmosphere by a hydrogen transfer reaction from decalin, which was simultaneously dehydrogenated to tetralin and naphthalene with the evolution of hydrogen gas. In comparison with metal species, Pd- and Ru-supported carbon catalysts maintained the hydrogenation activity for a longer time and with a lower evolution of hydrogen than Pt or Rh. The dehydrogenation of decalin was mainly observed not on the metal surfaces, but on the carbon surfaces over Pd-supported carbon. Stabilization of the monomers will be able to suppress the coking which occurs with repolymerization in long running process. Received: July 19, 2000 / Accepted: March 16, 2001     

Effects of resource availability,predators, conspecifics and heterospecifics on decorating behaviour by the majid crab <Emphasis Type="Italic">Tiarinia cornigera</Emphasis>

Utilization of algae for decorating by the intertidal majid crab Tiarinia cornigera was examined by laboratory experiments in relation to availability of algae, presence of a predator, and the presence of conspecific and heterospecific crabs. Different availabilities of decorating materials had a positive correlation on decorating amount by juveniles, while the correlation was not so clear in subadults. The amount of decorating decreased with increasing density of conspecific crabs in the presence of a predator, but there was so clear relationship in the absence of a predator. The decrease in decorating under high density could be due to intraspecific aggression, because the superior crab, in fighting, was found to be decorated with more algae. Tiarinia cornigera was found to be superior to the co-occurring different majid species Micippa platipes in fighting. When T. cornigera and M. platipes were housed together, the former was decorated with more algae than the latter in the presence of a predator, but in the absence of a predator, the amount of algae was not different. Thus, presence of a predator may motivate intraspecific competition in T. cornigera as well as interspecific competition between T. cornigera and M. platipes for decorating materials.     

Influence of dispersants on bioconcentration factors of seven organic compounds with different lipophilicities and structures

Seven compounds with different lipophilicities and structures—1,3,5-trichlorobenzene, pentachlorobenzene, acenaphthylene, 1,4-dimethyl-2-(1-methylphenyl)benzene, 4-ethylbiphenyl, 4,4′-dibromobiphenyl, and 1,1,1-trichloro-2,2-bis(4-chlorophenyl)ethane—were subjected to bioconcentration tests in carp at concentrations below the water solubilities of the compounds in the presence or absence of a dispersant (either an organic solvent or a surfactant). The bioconcentration factors (BCFs) of the compounds were on the order of 10²–10⁴. The BCF values remained in the range of 15–49% for all the compounds, whether or not a dispersant was present, i.e., the BCF values in the presence of an organic solvent or a surfactant at a concentration below the critical micelle concentration were not significantly smaller than the BCF values in the absence of the solvent or surfactant. This result indicates that the dispersants had no influence on the evaluation of the bioconcentration potential of these test substances.     

Aromatization of waste polyolefin pyrolysate over H-ZSM-5 zeolite-supported gallium oxide catalysts

H-ZSM-5 zeolite-supported gallium oxides were studied as aromatization catalysts for polyolefin pyrolysate. The catalysts were prepared by a conventional physical mixing method with a gallium content of 1.0 and 4.5 wt% and were reduced in flowing hydrogen at 585°C. To test their activity, a polyolefin sample was pyrolyzed and passed over a heated catalyst layer; the product was analyzed by gas chromatography/mass spectrometry. A continuous-flow fixed-bed reactor was used for aromatization of a model gas of polyolefin pyrolysate. For chlorine-free sources at 450°C, the catalyst with only 1.0 wt% gallium exhibited activity comparable to a gallium silicate catalyst. For chlorine-contaminated sources, the catalyst with 4.5 wt% gallium sustained catalytic activity for long periods. From the activity test results, it was found that zeolite-supported gallium catalysts prepared by the physical mixing method are suitable for converting polyolefin into aromatic hydrocarbons.     

Indirect prediction of surface ozone concentration by plant growth responses in East Asia using mini-open top chambers

We developed small and mobile open top chambers (mini-OTC) measuring 0.6 m (W)?×?0.6 m (D)?×?1.2 m (H) with an air duct of 0.6 m (W)?×?0.23 m (D)?×?1.2 m (H). The air duct can be filled with activated charcoal to blow charcoal filtered air (CF) into the chamber, as opposed to non-filtered ambient air (NF). Ozone sensitive radish Raphanus sativus cv. Red Chime and rosette pakchoi Brassica campestris var. rosularis cv. ATU171 were exposed to NF and CF in mini-OTCs at different locations in East Asia. A total of 29 exposure experiments were conducted at nine locations, Shanghai, China, Ha Noi, Vietnam, Lampang, Phitsanulok and Pathumtani, Thailand, and Hiratsuka, Kisai, Abiko and Akagi, Japan. Although no significant relationships between the mean concentrations of ambient O₃ during the experimental period and the growth responses were observed for either species, multiple linear regression analysis suggested a good relationship between the biomass responses in each species and the O₃ concentration, temperature, and relative humidity. The cumulative daily mean O₃ (ppb/day) could be indirectly predicted by NF/CF based on the dry weight ratio of biomass, mean air temperature, and relative air humidity.     

Enzymatic Degradation of Poly(l-Lactic Acid): Effects of UV Irradiation

Amorphous and crystallized poly(l-lactic acid) (PLLA-A and PLLA-C, respectively) films were prepared, and the proteinase K-catalyzed enzymatic degradation of UV-irradiated and non-irradiated PLLA-A and PLLA-C films was investigated for periods up to 10 h (PLLA-A) and 60 h (PLLA-C). The molecular weights of both the PLLA-A and PLLA-C films can be manipulated by altering the UV irradiation time. The enzymatic weight loss values of the UV-irradiated PLLA films were higher than or similar to those of the non-irradiated PLLA film, when compared with the specimens of same crystallinities. UV irradiation is expected to cause the PLLA films to undergo chain cleavage (a decrease in molecular weight) and the formation of C=C double bonds. It seems that the acceleration effects from decreased molecular weight on enzymatic degradation were higher than or balanced with the disturbance effects caused by the formation of C=C double bonds. After enzymatic degradation, a fibrous structure appeared on the spherulites of the UV-irradiated PLLA-C film. This structure may have arisen from chains containing or neighboring on the C=C double bonds, which were enzymatically undegraded and assembled on the film surface during enzymatic degradation. The results of this study strongly suggest that UV irradiation will significantly affect the biodegradation behavior of PLLA materials in the environment.     

Unique bioconcentration characteristics of new aryl fluoroalkyl ethers in common carp (Cyprinus carpio)

The bioconcentration factors (BCFs) of seven new aryl fluoroalkyl ethers--four bis-4-tetrafluoroethoxyphenyl-type (bis-type) compounds and three mono-4-tetrafluoroethoxyphenyl-type (mono-type) compounds--were obtained by bioconcentration tests using common carp. The BCFs of 4 of the 7 ethers were higher than 5000, indicating their high bioconcentration potential. The bioconcentration characteristics of the bis-type compounds were different from those of the mono-type compounds and non-fluoro diphenylmethanes with a similar skeleton structure to the bis-type compounds, in taking longer to reach a plateau and having a slower elimination rate and in their distribution patterns in the fish body. The BCF of 1 bis-type compound was much higher than the value predicted by an accepted correlation equation between BCF and P(ow). In addition, the logP(ow) of the bis-type compounds calculated by commercially available computer software was remarkably different from that measured.