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71.
Synopsis Fish assemblages at an artificial reef site, a natural reef site and a sandy-mud bottom site, on the shelf (depth 130 m) off Iwate Prefecture, northern Japan, were surveyed by using a bottom trammel net from May 1987 to March 1993. A total of 12 173 fishes of 48 species were recorded. Physiculus maximowiczi was dominant and comprised 69% of the total numerical abundance. Total fish number was lowest in March at all the 3 sites when P. maximowiczi migrated to deeper and warmer waters. Assemblage equitability and species diversity also varied seasonally in accordance with the abundance fluctuation of P. maximowiczi. P. maximowiczi, Alcichthys alcicornis and Hexagrammos otakii were more abundant at the artificial reef and natural reef sites, while Dexistes rikuzenius and Hemitripterus villosus were more abundant at the sandy-mud bottom site; total fish abundance was largest at the artificial reef site mainly due to the large number of P. maximowiczi. Species richness was similar among sites, but equitability, and consequently species diversity, was lowest at the artificial reef site. The main effect of the artificial reef seemed the attraction of P. maximowiczi from nearby bottoms, especially from natural rocky reefs; its large abundance determined the structure of the artificial reef fish community.  相似文献   
72.
J.Y. ROH, H.W. PARK, B.R. JIN, H.S. KIM, Y.M. YU AND S.K. KANG. 1996. Four Bacillus thuringiensis isolates from soil samples produced parasporal inclusions which were non-toxic to insects. The isolates were named B. thuringiensis NTB-1, NTB-2, NTB-3 and NTB-4. The parasporal inclusions were shown to be ovoid by phase contrast and scanning electron microscopy. The serotypes of the four isolates were determined by agglutination using 33 antisera; NTB-1 and NTB-4 seemed to be subsp. isruelensis ,and NTB-2 seemed to be subsp. pondzcheriensis . NTB-3 did not react with the 33 antisera. However, comparison of parasporal protein and plasmid DNA patterns of the four isolates with those of 15 known non-toxic B. thuringiensis strains demonstrated that the four isolates are novel.  相似文献   
73.
Acetylation dramatically effects both the solution properties and the metal induced precipitation of alginates. The presence of acetyl groups on both bacterial and seaweed alginate polymers marginally increased the weight average molecular weight (Mw) of each polymer by 7% and 11%, respectively. Acetylated bacterial alginate showed a significant increase in solution viscosity compared to its deacetylated counterpart. However microbial acetylation of seaweed alginate did not change its solution viscosity. Acetylation altered the calcium induced precipitation of both alginates. The presence of acetyl groups decreased the ability of each polymer to bind with calcium but increased their ability to bind with ferric Ion (Fe3+). By controlling the degree of acetylation on the alginate chains, it was possible to modify solution viscosity and cation induced precipitation of these polymers.  相似文献   
74.
Summary The cellobiose oxidizing enzyme of the newly isolated cellulolytic bacterium Cytophaga sp. LX-7 was produced extracellularly when grown on cellulose or other saccharides, which was previously noted only in fungi. The enzyme could use not only cellobiose, maltose, glucose and other saccharides but also cellulose as substrates, and use dichlorophenol indophenol and oxygen as electron acceptors.  相似文献   
75.
Nickel (Ni) toxicity to growth and photosynthesis was studied in four strains of Scenedesmus acutus f. alternans. Effects of Ni dosage and duration of exposure on growth and photosynthesis were strain specific. Large differences in responses of both growth and photosynthesis to Ni were detected between three resistant strains (B4, Cu-Tol, and Ni-Tol) and one sensitive strain (UTEX 72). Growth of UTEX 72 was 18 times more sensitive to Ni than those of the three resistant strains. The order of Ni dosages (fmol Ni/pg cell dry weight) causing 50% inhibition (D150) of growth rates in the four strains was Ni-Tol (10.5) > B4 (8.19) > Cu-Tol (4.60) > UTEX 72 (0.25). The effect of Ni dosage on photosynthetic rate as percentage of control corresponded to a saturation curve and was a strong function of duration of exposure. The DI50s of photosynthetic rates were 3.5 times lower in UTEX 72 than in the three resistant strains, and in all four strains they decreased sharply with the increase in duration of exposure. The order of the four strains in DI50s of photosynthetic rate was B4 (58.2) > Cu-Tol (38.0) > Ni-Tol (28.9) > UTEX 72 (8.24) for 6-h exposure and Ni-Tol (2.88) > Cu-Tol (1.30) > B4 (1.01) > UTEX 72 (0.15) for 24-h exposure. The DI50s of photosynthetic rate for 6-h exposure were higher than those of growth rate in all four strains, and for 24-h exposure they were lower, except in UTEX 72. Thus, the relative Ni sensitivity of growth and photosynthesis of the four strains depends on the duration of exposure. The results of factorial analysis of variance suggested that Ni toxicity to photosynthesis is a consequence of a strong interaction among strain, Ni dosage, and duration of exposure.  相似文献   
76.
生物复苏——大绝灭后生物演化历史的第一幕   总被引:12,自引:1,他引:11  
生命史是一部生物界短期,快速剧变与长期,慢速稳定相互交替的历史。大绝灭(即集群绝灭)事件反映了全球环境的大突变,点断了地质历史中的生命记录及其发展历程,预示着生物界的演化出现了最有意义的飞跃,近年来尝试研究大绝灭后全球生物界的残存-复苏及其基本型式,并探索复苏的控制因素,标志着地质科学中一个重心的转移(即从大绝灭转向其后的生物残存与复苏的研究)。生物复苏揭示了大绝灭后生物演化历史的第一幕,其研究的  相似文献   
77.
酿酒酵母属(S. cereviae)变异株和粟酒裂殖酵母属(S. pombe)变异株进行属间原生质体融合得到融合株SPSC,该融合株比S. cereviae具有强的自身絮凝能力。以葡萄糖浓度150g/L的底物在30~44℃的温度范围内进行摇瓶厌氧发酵,获得最佳温度范围为34~38℃,最高发酵温度为40℃。在有效容积2.35L悬浮床反应器中,在pH值3.0~5.0范围内进行连续发酵,获得最适发酵pH为3.5~4.5。  相似文献   
78.
黄毛鼠(Rattus rattides)在群居(4只/笼)时体重及性器官,如睾丸和附睾的增长都受到了极大的抑制;血清中睾酮含量的迅速上升以及成熟精子在附睾的曲细精管中出现的时间也比单独关养的晚。成年雄鼠的笼填充物的气味能够诱导幼年雄鼠体重,睾丸的总量和长度以及血清中睾酮的含量的增加。  相似文献   
79.
邱高峰  堵南山 《动物学报》1996,42(4):349-354
运用电镜和细胞化学技术研究了日本沼虾精子的形态结构,结果表明:日本沼虾精子属无鞭毛精子,为单一棘突型,呈图钉样,由主体和棘突构成;主体部分为帽状体,精核和细胞质带。帽状体由约20根辐射状纤丝组成,纤丝上具横纹,并汇合帽状基部,由此向后延伸形成棘突。  相似文献   
80.
Three different DNA mapping techniques—RFLP, RAPD and AFLP—were used on identical soybean germplasm to compare their ability to identify markers in the development of a genetic linkage map. Polymorphisms present in fourteen different soybean cultivars were demonstrated using all three techniques. AFLP, a novel PCR-based technique, was able to identify multiple polymorphic bands in a denaturing gel using 60 of 64 primer pairs tested. AFLP relies on primers designed in part on sequences for endonuclease restriction sites and on three selective nucleotides. The 60 diagnostic primer pairs tested for AFLP analysis each distinguished on average six polymorphic bands. Using specific primers designed for soybean fromEco RI andMse I restriction site sequences and three selective nucleotides, as many as 12 polymorphic bands per primer could be obtained with AFLP techniques. Only 35% of the RAPD reactions identified a polymorphic band using the same soybean cultivars, and in those positive reactions, typically only one or two polymorphic bands per gel were found. Identification of polymorphic bands using RFLP techniques was the most cumbersome, because Southern blotting and probe hybridization were required. Over 50% of the soybean RFLP probes examined failed to distinguish even a single polymorphic band, and the RFLP probes that did distinguish polymorphic bands seldom identified more than one polymorphic band. We conclude that, among the three techniques tested, AFLP is the most useful.  相似文献   
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