Confirmation of colonization of degrading bacterium strain SC-17 on poly(3-hydroxybutyrate) cast film

To clarify the mechanism of microbial degradation owing to colonization ofPseudomonas sp. strain SC-17 on a poly(3-hydroxybutyrate) (PHB) cast film surface, morphological and spectroscopic analyses of the degraded film were investigated and colonization kinetics on the films is discussed. By spectroscopic analysis of unique hemispherical degradation marks, cells of strain SC-17 adhering to the marks' surface were confirmed. To account for the hemispherical hole formation and their linear enlargement with culture time, a three-dimensional colony growth model toward the interior of the film was developed. The model explained the hemispherical hole formation well. It was concluded that the hemispherical holes resulted from the colonization of strain SC-17 on the film surfaces. It was further determined that the microbial degradation by strain SC-17 is initiated from small pits formed on the PHB film surface.     

Genetic stock structure of the swordfish (Xiphias gladius ) inferred by PCR-RFLP analysis of the mitochondrial DNA control region

Restriction fragment length polymorphism (RFLP) analysis was performed on PCR amplified DNA fragments containing the control region of the swordfish (Xiphias gladius Linnaeus, 1758) mitochondrial DNA. A total of 456 individuals comprising 13 local samples (six Pacific, three Atlantic, the Mediterranean Sea, two Indian Ocean and the Cape of Good Hope) were surveyed with four endonucleases (Alu I, Dde I, Hha I and Rsa I), yielding a total of 52 composite genotypes. Within-sample genotypic diversity (H) was high ranging from 0.702 to 0.962 with a value of 0.922 for the pooled sample. Significant geographic variation in the frequencies of genotypes and restriction patterns was revealed. The Mediterranean sample was highly distinct from all other samples. Further, Rsa I digestion revealed high levels of polymorphism in all but the Mediterranean samples, indicating that exogenous swordfishes rarely enter that body of water. Heterogeneity between the North and South Atlantic samples was significant, both of which differed from those of the Pacific. In contrast, the Indian Ocean samples were not significantly different from the samples of South Atlantic and Pacific. Genetic differentiation among the Pacific samples was low. The results indicate that the world-wide swordfish population is genetically structured not only among, but also within ocean basins and suggest that gene flow is restricted despite the absence of geographic barriers. Received: 28 August 1996 / Accepted: 2 October 1996     

Effect of aging time on the availability of freshly precipitated ferric hydroxide to coastal marine diatoms

Cell growth and iron uptake of the coastal marine diatoms Chaetoceros sociale and Thalassiosira weissflogii were studied in the presence of short-aged amorphous ferric hydroxide (am-Fe(III)) media. These were prepared by aging for 1 day, 3 days, and 3 weeks after adding a small amount of ferric iron acidic stock solution to autoclaved filtered seawater and were experimentally measured in culture experiments at 10°C for C. sociale and 20°C for T. weissflogii. The order of cell yields for both species was: 1-day aged am-Fe(III) >3-day aged am-Fe(III) >> 3-week aged am-Fe(III) media. The iron uptake rates by C. sociale during 0–1 day in 1 day and 3-day aged am-Fe(III) media were about two-thirds and one-fourths, respectively, lower than that in the direct Fe(III) input medium containing C. sociale into which an acidic Fe(III) stock solution was added directly. The longer aging time of am-Fe(III) in media results in reducing the supply of bioavailable iron in the media by the slower dissolution rate of am-Fe(III) with the longer aging time. These results suggest that the chemical and structural changes of freshly precipitated amorphous ferric hydroxide with short aging time affect their ability, such as iron solubility and dissolution rate to supply bioavailable iron for the phytoplankton growth. The chemical and structural conversion of solid iron phases with time is one of the most important processes in changing the supply of available iron to marine phytoplankton in estuarine and coastal waters and in iron fertilization experiments.     

Nest-size variation reflecting anti-predator strategies in social spider mites of<Emphasis Type="Italic"> Stigmaeopsis</Emphasis> (Acari: Tetranychidae)

The social spider mites (Acari: Tetranychidae) of Stigmaeopsis weave dense nests on the underside of host leaves. Four species occur on the leaves of bamboo in Japan: Stigmaeopsis longus, S. celarius, S. takahashii and S. saharai. We initially reconfirmed the occurrence of distinct variation in nest size among the species. Based on the hypothesis that this variation plays a role in protecting the spider mites from predators, we looked at the behavior of the natural enemies that occur on the host plants along with members of Stigmaeopsis. We found considerable variation in the ability of nests to protect the spider-mite eggs. The smallest nests protected the eggs against three predators, whereas the largest nests protected the eggs against only one predator species. So, decreases in nest size increased egg defense. Thus we concluded that nest-size variation reflects a strategy for reducing predation.Communicated by D. Gwynne     

Effects of higher-order structure of poly(3-hydroxybutyrate) on its biodegradation. II. Effects of crystal structure on microbial degradation

As one of a series of studies concerning the relationship between the higher-order structure and the biodegradability of a biodegradable plastic, the effects of the crystal structure of the plastic on microbial degradation were investigated. Bacterial poly(d-(–)-3-hydroxybutyrate) (PHB) films which had a wide range of crystallinity were prepared by the melt-quenching method. Results of the microbial degradation indicated that the development of crystallinity evidently depressed the microbial degradability. From scanning electron microscopy (SEM) observations, it is suggested that the microbial degradation proceeded in at least two manners. One was preferential degradation of the amorphous region leaving the crystalline lamellae intact, which was considered to be a homogeneous enzymatic degradation over the surface. The other was nonpreferential spherical degradation on the surface. The SEMs indicate that the spherical holes were the result of colonization by degrading bacteria. The holes varied in size and number with the change of crystal structure. Therefore, it is considered that the crystal structure of PHB also influenced the physiological behavior of the degrading bacteria on the PHB surface.     

膜采样离线分析与在线测定大气细粒子中元素碳和有机碳的比较

针对普遍采用的膜采样离线分析与在线测定大气细粒子中元素碳和有机碳的方法进行了比较分析. 2006年1月～2007年4月期间在北京大学校园内应用膜采样离线分析和在线分析分季节同时测定了PM_2.5中元素碳（EC）和有机碳（OC）,并将结果进行对比.结果显示,膜采样法测得的OC约为在线仪器测得的OC的2倍, 2种方法差别主要体现在对OC的测量上.不加平行板有机物扩散吸收管引入OC比较大的正误差,而加平行板有机物扩散吸收管又将引入OC的负误差,约10%.同时采用平行板有机物扩散吸收管和后置膜的离线分析方法同在线观测的结果具有比较好的一致性.     

An overlooked side effect of nest-scattering behavior to decrease predation risk (Acari: Tetranychidae,Stigmaeidae)

The number of nests containing egg masses a female makes over her lifetime and the pattern of scattering nests vary among species in a genus of nest-weaving spider mites (Stigmaeopsis). We hypothesized that the scattered nests of small nest builders have a previously overlooked indirect effect in that the void nests created after predation take on a new role as hindering devices that effectively decrease predator searching efficiency. First, we demonstrated that the experimental design used in this study is a good reflection of the nest distribution pattern of Stigmaeopsis takahashii (an intermediate-sized nest builder) in the field. Using this species as a model, we tested how different nest-scattering patterns affect the predator to examine how scattering may indirectly provide an anti-predation strategy by increasing a predators searching time. Next, we observed how artificially arranged void nests disturb predatory behavior in both starved and fully fed predator females and showed that void nests have a strong hindering effect on predators. Thus, we concluded that the nesting behavior of this mite species not only has anti-predator effects but must also have a stabilizing effect on predator–prey interaction systems at the population level.     

Isomer‐specific determination and toxic evaluation of potentially hazardous coplanar PCBs,dibenzofurans and dioxins in the tissues of “Yusho” PCB poisoning victim and in the causal oil

In the light of new discoveries on the extremely toxic non‐ortho coplanar 3,3’,4,4'‐tetra‐ (T₄CB), 3,3’,4,4’,5‐penta‐(P₅CB) and 3,3'4,4’,5,5'‐hexachlorobiphenyl (H₆CB) and their mono‐ and di‐ortho analogs, tissue samples of a Yusho poisoning victim and Yusho causal oils were subjected to a thorough congener/isomer‐specific investigation for polychlorinated biphenyls (PCBs), polychlorinated dibenzofurans (PCDFs), polychlorinated dibenzo‐p‐dioxins (PCDDs). Among the many PCB congeners detected in Yusho oil, non‐ortho coplanar T₄CB constituted 3.1%, P₅CB‐0.17% and H₆CB‐0.0072% in total PCBs. Their concentrations in liver and adipose tissue were 130–700 (T₄CB), 54–720 (P₅CB) and 50–380 (H₆CB) pg/g on wet weight basis. The observed concentrations in adipose tissue were two to four fold higher than that detected in unexposed individuals. Among the PCDFs identified, toxic 2,3,7,8‐substituted isomers including 2,3,4,7,8‐P₅CDF were the dominant ones. Tetra‐ through hepta‐CDDs were detected in the oil, whereas octa‐CDD was the dominant isomer in the patient. A comparison with KC‐400 revealed enrichment of coplanar PCBs in Yusho oil along with toxic PCDFs. Enrichment was highest for 3,3'4,4'5,5'‐H₆CB followed by 3,3’,4,4'5‐P₅CB. A comparative toxic evaluation of these chemical groups in Yusho patient's adipose tissue based on “2,3,7,8‐T₄CDD Toxic Equivalent Analysis” revealed accountable toxic contribution from coplanar PCBs. This analysis also confirmed that 2,3,4,7,8‐P₅CDF was the principal causative agent in Yusho poisoning.