H．史密斯采集的中国紫草科植物

自H．Smith在二十,三十年代从我国采集的紫草科标本中鉴定出15属,36种,4变种,均属紫草亚科,其中包括附地菜属一新种,其中,这批标本本来应该包括更多的新种,如Johnston在1928年及以后描述的Microula rockii Johnst.,Onosma mertensioides Johnst.,O.adenopus Johnst.,Trionotis floribunda Johnst.,Kitagawa在六十年代描述的Lappula shanhsiensis Kitag.,本文作者和王庆瑞在八十年代描述的Microula pseudotrichocarpa W.T.Wang,M.turbinata W.T.Wang,M.turbinata W.T.Wang,M.floribunda W.T.Wang,Trigontis longipes W.T.Wang,T.corispermoides C.J.wang。只是由于这批柴草科标本未得到及时鉴定,才推迟了这10个种的发表。     

双歧杆菌和乳酸菌的一种简便快速计数法

当前,含双歧杆菌和乳酸菌的各种微生态调节剂正在国内外迅速发展。为确保这类制剂的质量,活菌计数极其重要。可是,由于这两类细菌都是厌氧菌,在计数方法上需要特殊的设备和较复杂的操作技术,因此现有方法还很不理想。我们根据高层半固体琼脂培养基具有良好厌氧性能的原理,在必要的条件试验基础上,提出了一种适用于双歧杆菌和乳酸菌等不产气厌氧菌的简便快速活菌计数法(下称“本法”),现简报如下。     

Modes and cuts in metabolic networks: complexity and algorithms

Constraint-based approaches recently brought new insight into our understanding of metabolism. By making very simple assumptions such as that the system is at steady-state and some reactions are irreversible, and without requiring kinetic parameters, general properties of the system can be derived. A central concept in this methodology is the notion of an elementary mode (EM for short) which represents a minimal functional subsystem. The computation of EMs still forms a limiting step in metabolic studies and several algorithms have been proposed to address this problem leading to increasingly faster methods. However, although a theoretical upper bound on the number of elementary modes that a network may possess has been established, surprisingly, the complexity of this problem has never been systematically studied. In this paper, we give a systematic overview of the complexity of optimisation problems related to modes. We first establish results regarding network consistency. Most consistency problems are easy, i.e., they can be solved in polynomial time. We then establish the complexity of finding and counting elementary modes. We show in particular that finding one elementary mode is easy but that this task becomes hard when a specific EM (i.e. an EM containing some specified reactions) is sought. We then show that counting the number of elementary modes is musical sharpP-complete. We emphasize that the easy problems can be solved using currently existing software packages. We then analyse the complexity of a closely related task which is the computation of so-called minimum reaction cut sets and we show that this problem is hard. We then present two positive results which both allow to avoid computing EMs as a prior to the computation of reaction cuts. The first one is a polynomial approximation algorithm for finding a minimum reaction cut set. The second one is a test for verifying whether a set of reactions constitutes a reaction cut; this test can be readily included in existing algorithms to improve their performance. Finally, we discuss the complexity of other cut-related problems.     

海洋病毒荧光显微计数法的优化与应用

【目的】建立一种快速、稳定、可靠的海洋病毒计数方法。【方法】海水水样经福尔马林固定后,滤过孔径为0.02μm的Anodisc Al2O3膜。滤膜经SYBR Green I染色后,在相应波长的激发光下进行观察。借助荧光显微镜目镜网格尺,计数视野中的病毒颗粒,换算后获得样品中病毒的浓度。【结果】对具体实验方法进行了优化,可快速、稳定地对海水中的病毒计数。【结论】建立了一种适用于国内实验条件的、可靠的海洋病毒计数方法。     

Characterization of microbial traits associated with glyphosate biodegradation in industrial activated sludge

Summary The microorganisms from two industrial (I1, I2) activated sludges that treat glyphosate (N-phosphonomethyl glycine) wastes and one domestic (D1) sludge were enumerated by microscopic examination and by the use of eight selective media. I1 and I2 had higher total counts but fewer pseudomonads and no yeasts. The enumerations correlated directly with traditional biological performance measurements. A total of 393 microbial strains were isolated from the sludges to correlate the occurrence and relationship of glyphosate-degrading activity (GDA) to 155 biochemical and morphological characteristics. Each activated sludge contained unique bacterial populations with the microbes treating industrial wastes, capable of utilizing a wide range of carbohydrates. Numerical taxonomy (arithmetic average linkage) using simple matching and Jaccard coefficients confirmed that there were five (D1), three (I1), and 12 (I2) clusters. GDA was found in only a small portion of the industrial clusters and did not correlate with any other characteristic tested, even though the GDA strains had a large phenotypic diversity. This suggests that GDA is not a universal trait and its expression requires enrichment through specific selective pressures.     

Rhizobium meliloti distribution in the soil following alfalfa inoculation

Summary Alfalfa seeds, inoculated with an antibiotic-resistantRhizobium meliloti strain, were planted in three replicated field plots at Clayton, N.C. Core samples were taken three times in the next year at 0, 10, and 20 cm from the edge of each plot. Soil subsamples were taken from within each core sample at 0, 6, 12, and 18 cm depths. The numbers of the inoculum Rhizobium strain in each soil subsample were determined by inoculation of alfalfa plants with diluted soil samples. In general the distribution of rhizobia showed some movement outward and downward in the soil. Lower counts were obtained at the surface during summer. The Rhizobium persistence pattern in the soil differed in the three plots which is consistent with the variability in Rhizobium numbers often observed in established alfalfa stands. Cooperative investigation of the United States Department of Agriculture, Science and Education Administration, Agricultural Research and the North Carolina Agricultural Research Service, Raleigh, North Carolina. Paper No. 6818 of the Journal Series of the North Carolina Agricultural Research Service at Raleigh.     

Reconstructing pedigrees: a combinatorial perspective

A pedigree is a directed graph that displays the relationship between individuals according to their parentage. We derive a combinatorial result that shows how any pedigree-up to individuals who have no extant (present-day) ancestors-can be reconstructed from (sex-labelled) pedigrees that describe the ancestry of single extant individuals and pairs of extant individuals. Furthermore, this reconstruction can be done in polynomial time. We also provide an example to show that the corresponding reconstruction result does not hold for pedigrees that are not sex-labelled. We then show how any pedigree can also be reconstructed from two functions that just describe certain circuits in the pedigree. Finally, we obtain an enumeration result for pedigrees that is relevant to the question of how many segregating sites are needed to reconstruct pedigrees.     

A new preferential medium for enumeration and isolation of desert actinomycetes

In order to facilitate the discovery of novel actinomycetes from the Egyptian deserts, which can be useful as new sources for bioactive metabolites, different media for enumeration and isolation of desert actinomycetes have been tested. For this purpose, 30 soil samples from different six sites representing the Western and Eastern deserts of Egypt were collected. The two deserts are considered hyper-arid and the soil characteristics were determined. The media used were glucose–yeast extract agar, soil extract agar and a new minimal medium (MM) containing glucose, yeast extract and mineral salts. The effects of the soil characteristics on the total viable actinomycete counts on the three media were evaluated. The results showed that the highest actinomycete count in samples from five out of six sites was obtained on MM. Also MM was more selective for actinomycetes and significantly decreased the number of fungal colonies and to a lower extent the number of bacterial colonies. Moreover, it supported the development of different and diverse groups of actinomycetes. From the results obtained in this study, MM is a new useful medium for enumeration and selective isolation of actinomycetes from the desert soils.