嗜热甲酸甲烷杆菌602B_3与拟杆菌5G—102的混合培养

研究了嗜热甲酸甲烷杆菌(Methanobacterium thermoformicicum)602B_3与发酵糖蜜产生C0_2和H_2的拟杆菌(Bacteroides sp.)5G-102的人工可配伍性。确定了它们混合培养的适宜培养基组分为(g/L):CaC0_3 50.0,NaHCO_3 4.0,Na_2S 0.16,NH_4Cl 1.07,K_2HPO_4 1.04,MgCl_2 0.19,糖蜜40(V/V),自来水IL,起始pH 6.8～7.2。混合培养物在60℃培养48h,甲烷产量达到最高,约45mmol/L。人工混合培养成功为进一步研究其在提高石油采收率工艺中的可用性提供了前提。     

Identification and estimation of a QTL model and its effects

 A joint segregation analysis of a genetic system and the effects of QTLs based on the six populations P₁, F₁, P₂, B₁, B₂ and F₂ is proposed in this paper. The major steps were as follows. Firstly, under the supposition that the segregating population was composed of component distributions controlled by a major gene(s) and modified by both polygenes and environments, four groups and 17 types of genetic models, including a one major-gene model, a two major-gene model, a polygene model, and a mixed one-major gene and polygene model, were set up. Secondly, the joint maximum-likelihood function was constructed from the six generations so as to estimate the parameters of component distributions through an EM algorithm. Thirdly, the best-fitting genetic model was chosen according to Akaike’s information criterion, a likelihood-ratio test, and tests for goodness of fit. Fourthly, the related genetic parameters, including gene effects, as well as the genetic variances of major genes and polygenes, were obtained from the estimates of component distributions. Finally, the individuals in segregating populations were classified into their major-gene genotypes according to their posterior probabilities. An example of the genetic analysis of plant height of a rice cross between Nanjing No. 6 and Guangcong was used to illustrate the above procedure. The method was especially appropriate to those crops with easy to obtain hybrid seeds. Received: 11 February 1998 / Accepted: 28 May 1998     

福建省畲族近亲婚配的遗传学研究

作在进行福建省畲族人口健康素质机样调查中,对畲族的近亲结婚率、平均近亲系数、探亲结婚类型、近亲结婚的有害遗传应用以有异族通婚进行研究。１９９４年至５月,在福建省的福安市穆阳乡、漳浦县赤岭乡和上杭县官庄乡,调查畲族婚姻６３３５对,其中近亲结婚５４对。一级表亲占近亲结婚的９２．５８％。近亲结婚率０．８５％,平均近亲系数５．７２×１０,异族通婚率４１．８８％。近亲结婚率和平均近亲系数与国内报道的３１个     

褐飞虱和白背飞虱混合为害对水稻营养生长的影响

研究了褐飞虱和白背飞虱混合种群的取食为害对水稻营养生长的影响 .结果表明 ,两种飞虱的成虫干重、水稻叶面积和其地上部干重因虫口密度的增加而下降 ,变化幅度与种间数量组合有关 ;水稻比叶重随为害程度的加重而加大 ;在褐飞虱与白背飞虱种间以 1∶3、2∶2和 3∶1比例的 3种组合处理中 ,虫体总干重 (X)与稻株地上部损失量 (Y)之间存在着极显著的线性关系 ,线性方程分别是Y =69 1 7 30 43X、Y =1 72 48 36 51X和Y =87 59 37 67X ,b值相应为 30 43、36 51和 37 67.     

Analysis of vegetation structural diversity by Burnaby's similarity index

The application of Burnaby's similarity index is discussed by using structural data from mediterranean vegetation. The index, suggested to compare objects described by characters measured on different scales (mixed data), was applied in a fuzzy theory context. Ordinations of vegetation relevés and structural characters by joint plots have been obtained. These are very useful to map vegetation structural diversity in multidimensional spaces and to test the efficiency of an intuitive classification based on qualitative assessment.     

The relationship between foraging and shoal position in a mixed shoal of roach (Rutilus rutilus) and chub (Leuciscus cephalus): a field study

Feeding rates of mixed shoals of juvenile roach and chub were observed in a shallow stream near Cambridge (UK). Roach at the front of the shoal had significantly higher feeding rates than roach at the back and than chub in either front or back positions. Position in the shoal also had a significant effect on the kind of food consumed, with front roach feeding more on plankton and back roach more on bottom food. Altogether 36 fish from the stream were caught and marked. Half of these were deprived of food and the other half well-fed for 3 days in captivity. After release 36% of them joined their old shoal again. Individuals from the starved group occupied front positions significantly more often than well-fed fish, but after 2 days this difference disappeared.     

鲮鱼和二代混精鲮鱼低温耐受能力的差异

采用LKB循环冷却装置以程序降温方式比较鲮鱼及二代混精鲮鱼(草鱼混精鲮或多精混精鲮再用草鱼精液进行混精受精所得子代)的耐寒性能。无论是在7.0℃条件下的耐受时间,还是对低温耐受的极限,二代混精鲮鱼均优于鲮鱼,但这种改善是有限的。作者认为,混精受精法不能从根本上解决鲮鱼的不耐寒性能。应该寻求其他更有效的育种途径。     

共生发酵无醇饮料新工艺的研究

随着经济的发展,食品结构的改变,人们对饮料的要求越来越高,而且朝着原料天然化,营养保健型发展。现有的配制饮料或单菌种发酵饮料,都无法满足这种需求。因此,开发一种新型饮料已成为国内外研究的方向。 一种发酵产品的内含,除与工艺条件和     

Identification of mixed genotypes in Helicobacter pylori from gastric biopsy tissue by analysis or urease gene polymorphisms

Abstract PCR-RFLP analysis of the urease A and B genes was used to investigate the frequency that Helicobacter pylori from gastric biopsy specimens comprised genotypically distinct strains. Seventy-five strains of H. pylori from 44 subjects from four geographically diverse locations were examined and 31 distinct urease gene profiles were identified. For most cultures, the totals of the RFLP sizes were within 4% of the 2.41-kb PCR product. Five strains were genomically more complex suggesting they contained a mixture of related genotypes. The validity of the test was confirmed by analysis of a known strain mixture and of single colony picks from biopsy cultures. Urease gene PCR-RFLP profiling was shown to be more sensitive than ribotyping for determining the genotypic homogeneity of H. pylori .     

Interspecific competition among larvae ofHemipyrellia ligurriens (Calliphoridae) andBoettcherisca formosensis (Sarcophagidae) (Diptera)

1. The effects of larval rearing density and species relative proportions on life-history parameters of two necrophagous Diptera, Hemipyrellia ligurriens (Wiedemann) (Calliphoridae) and Boettcherisca formosensis Kirner and Lopes (Sarcophagidae), were investigated in mixed cultures. Larval rearing density had a significant effect on larval to adult survivorship, duration of immature development, adult size and relative performance (measured by the composite index of performance, r′) of both species. However, species relative proportions affected adult size of both flies and the duration of immature development of B. formosensis only.
2. B. formosensis had a higher survivorship than H. ligurriens in all mixed cultures and showed a similar survivorship pattern to that in pure cultures. By contrast, survivorship of H. ligurriens was lower in mixed than in pure cultures.
3. H. ligurriens adults reared from mixed cultures were smaller than those from pure cultures of comparable density, but B. formosensis adults from pure and mixed cultures were of similar size.
4. The results suggest that competition between B. formosensis and H. ligurriens larvae was asymmetric and the former was the superior competior.
5. At low larval densities in mixed cultures, the presence of H. ligurriens enhanced the performance (as measured by r′) of B. formosensis, a consequence of suspected interspecific facilitation of larval growth.