一株卡他布朗汉姆菌的重新鉴定

目的对中国医学细菌保藏管理中心库藏的一株卡他布朗汉姆菌CMCC(B)29103株进行重新鉴定。方法用营养琼脂培养基培养CMCC(B)29103株,对其进行形态观察、生理生化特性、脂肪酸组分、分子生物学等多相鉴定,同时与模式株DSM25388T相对照;分析CMCC(B)29103株的特征属性、进化位置以及与Acinetobacter indicus模式株DSM25388T的同源性。结果形态学特性、生理生化以及脂肪酸组分构成均与DSM25388T株十分相似,仅存在个别差异;16 S rRNA基因序列比对显示,CMCC(B)29103株与Acinetobacter(不动杆菌属)相近,与模式株DSM25388T相似性最高,为99.85%。基于Acinetobacter属所有成员的16 S rRNA和rpo B基因的系统进化分析均显示CMCC(B)29103与DSM25388T稳定聚类成一个独立分支,且二者的DNA-DNA同源性为78.3%。结论CMCC(B)29103株属于Acinetobacter indicus种,与模式株DSM25388T为不同的菌株,可将其更名为Acinetobacter i ndicus。     

Synergistic degradation of benzylpenicillin by aPseudomonas strain and aFusarium strain

APseudomonas sp. and aFusarium sp. were isolated from pasture soil. The organisms grew syntrophically on a mineral medium with benzylpenicillin as carbon and nitrogen source. During synergistic degradation of the antibiotic, benzylpenicilloic and benzylpenilloic acid were intermediates. Activities of both organisms were necessary for further decomposition, during which the phenylacetate side chain was degraded. 6-Aminopenicillanic acid did not occur. During syntrophic growth, a red pigment appeared in fungal hyphae growing through bacterial colonies.     

Comparison of cellular strain with applied substrate strain in vitro

Strain magnitudes within tenocytes undergoing substrate tensile strain are not well defined. It was hypothesized that strain magnitudes at the cellular level would reflect those of the applied substrate (equibiaxial or uniaxial) strain. A vacuum-operated device was used to apply equibiaxial or uniaxial tension to a flexible substrate upon which tenocytes were cultured in monolayer. Images of tenocytes labeled with Fura-2, to detect free intracellular calcium ions, and MitoFluor Green, to detect mitochondria, were taken prior to strain and for 20 min during application of static strain. A custom-written, texture correlation program computed strain magnitudes in the cell based on the change in pixel pattern displacements between images of non-strained and strained cells. On average, cellular strain was approximately 37+/-8% and 63+/-11% of the applied equibiaxial and uniaxial substrate strain, respectively. The largest cell strains were detected in cells oriented parallel to the direction of applied uniaxial tensile strain. However, strain magnitudes within a cell were heterogeneous. The variance in strain magnitude within and among tenocytes is dependent on cell orientation, cell stiffness, cytoskeleton organization, subcellular organelles, or placement and type of cell-substrate contacts. Results of the present study indicate that cultured tenocytes experience a moderate fraction of the applied substrate strain.     

Clostridial strain degeneration

Abstract: Strain degeneration, the loss of the capacity to produce solvents and form spores, typically occurs when Clostridium acetobutylicum and related clostridia are repeatedly subcultured in batch culture or grown in continuous culture, as opposed to being grown from germinated, heat-treated spores. Several mechanisms for degeneration have been identified thus far. (i) Degeneration can be caused by excessive acidification of the culture during exponential growth. We present data interpreted to mean that C. beijerinckii (formerly C. acetobutylicum ) NCIMB 8052 cells ferment glucose to acetic and butyric acids at an uncontrolled rate, so that, during rapid growth, the rate of acid production can exceed the rate of induction of the solventogenic pathway enzymes. As a result, the medium pH drops to bactericical levels, and the cells cannot switch to solventogenesis and sporulation. The clostridia seem to be poised either to produce excess acids, or to initiate solventogenesis, depending on small differences in the rates of growth. (ii) We have isolated transposon-insertion mutants of C. beijerinckii NCIMB 8052 that are resistant to degeneration, suggesting the involvement of a regulatory region of the clostridial chromosome. (iii) Involvement of a global regulatory gene has been inferred in C. beijerinckii NCIMB 8052 which degenerates irreversibly in chemostat culture. (iv) Impairment of butanol formation due to a defect in NADH generation has been reported in an oligosporogenous strain which can revert to the non-degenerate phenotype. (v) In continuous culture, degenerate cells may be selected because they continue to divide, while the non-degenerate cells stop dividing and start differentiating.     

The relative value of strain and strain rate for defining intrinsic myocardial function

It is well accepted that strain and strain rate deformation parameters are not only a measure of intrinsic myocardial contractility but are also influenced by changes in cardiac load and structure. To date, no information is available on the relative importance of these confounders. This study was designed to investigate how strain and strain rate, measured by Doppler echocardiography, relate to the individual factors that determine cardiac performance. Echocardiographic and conductance measurements were simultaneously performed in mice in which individual determinants of cardiac performance were mechanically and/or pharmacologically modulated. A multivariable analysis was performed with radial and circumferential strains and peak systolic radial and circumferential strain rates as dependent parameters and preload recruitable stroke work (PRSW), arterial elastance (E(a)), end-diastolic pressure, and left ventricular myocardial volume (LVMV) as independent factors representing myocardial contractility, afterload, preload, and myocardial volume, respectively. Radial strain was most influenced by E(a) (β = -0.58, R(2) = 0.34), whereas circumferential strain was strongly associated with E(a) and moderately with LVMV (β = 0.79 and -0.52, respectively, R(2) = 0.54). Radial strain rate was related to both PRSW and LVMV (β = 0.79 and -0.62, respectively, R(2) = 0.50), whereas circumferential strain rate showed a prominent correlation only with PRSW (β = -0.61, R(2) = 0.51). In conclusion, strain (both radial and circumferential) is not a good surrogate measure of intrinsic myocardial contractility unless the strong confounding influence of afterload is considered. Strain rate is a more robust measure of contractility that is less influenced by changes in cardiac load and structure. Thus, peak systolic strain rate is the more relevant parameter to assess myocardial contractile function noninvasively.     

Catabolite regulation in a diauxic strain and a nondiauxic strain of Streptococcus bovis

Streptococcus bovis JB1 utilized glucose preferentially to lactose and grew diauxically, but S. bovis 581AXY2 grew nondiauxically and used glucose preferentially only when the glucose concentration was very high (greater than 5 mM). As little as 0.1 mM glucose completely inhibited the lactose transport of JB1. The lactose transport system of 581AXY2 was at least tenfold less sensitive to glucose, and 1 mM glucose caused only a 50% inhibition of lactose transport. Both strains had phosphotransferase systems (PTSs) for glucose and lactose. The glucose PTSs were constitutive, but little lactose PTS activity was detected unless lactose was the energy source for growth. JB1 had approximately threefold more glucose PTS activity than 581AXY2 (1600 versus 600 nmol glucose (mg protein)⁻¹(min)⁻¹. The glucose PTS of JB1 showed normal Michaelis Menten kinetics, and the affinity constant (K _s ) was 0.12 mM. The glucose PTS of 581AXY2 was atypical, and the plot of velocity versus velocity/substrate was biphasic. The low capacity system had a K_s of 0.20 mM, but the K_s of the high capacity system was greater than 6 mM. On the basis of these results, diauxic growth is dependent on the affinity of glucose enzyme II and the velocity of glucose transport. Received: 22 January 1996 / Accepted: 18 March 1996     

松花湖铜绿微囊藻无菌株和单藻株生长因素的研究

用毛细滴管洗净法从松花湖分离纯化出铜绿微囊藻(Microcystisaeruginosa)的单藻株和无菌株,研究了温度、照度、N、P、Fe各种因素对单藻株和无菌株生长的影响。结果表明,各种因素对单藻株和无菌株最大比增长率的影响差别不大,单藻株和无菌株分别在温度33℃,照度5000Lx(2000Lx)、NO3-N浓度1.2mg·L-1,PO43-P浓度0.06mg·L-1,柠檬酸铁铁浓度0.05mg·L-1(0.04mg·L-1)时,达到最大比增长率。在一定浓度范围内,随着N、P、Fe浓度的增加,单藻株比无菌株的最大增长量高得多,可见附着细菌的存在,能促进铜绿微囊藻的生长。从松花湖湖水中N、P和Fe含量以及温度和照度的情况看,松花湖的某些区域已经基本具备了水华发生的条件。     

Gradients of strain and strain rate in the hollow muscular organs of soft-bodied animals

The cylindrical shape of soft-bodied invertebrates is well suited to functions in skeletal support and locomotion, but may result in a previously unrecognized cost—large non-uniformities in muscle strain and strain rate among the circular muscle fibres of the body wall. We investigated such gradients of strain and strain rate in the mantle of eight long-finned squid Doryteuthis pealeii and two oval squid Sepioteuthis lessoniana. Transmural gradients of circumferential strain were present during all jets (n = 312); i.e. for a given change in the circumference of the outer surface of the mantle, the inner surface experienced a greater proportional change. The magnitude of the difference increased with the amplitude of the mantle movement, with circular muscle fibres at the inner surface of the mantle experiencing a total range of strains up to 1.45 times greater than fibres at the outer surface during vigorous jets. Differences in strain rate between the circular fibres near the inner versus the outer surface of the mantle were also present in all jets, with the greatest differences occurring during vigorous jetting. The transmural gradients of circumferential strain and strain rate we describe probably apply not only to squids and other coleoid cephalopods, but also to diverse soft-bodied invertebrates with hollow cylindrical or conical bodies and muscular organs.     

Ploidy level in Streptomyces cerevisiae strain 15B-P4 strain]

Hybridization analysis of seven clones of Saccaromyces cerevisiae 15B-P4 strain, which were obtained from different cultures, was carried out. Yeast strains taken from the Peterhoff breeding stocks were kept in the laboratory of genetics at Biological Institute of Irkutsk University from 1970. Increase in the number of prototrophic segregants was shown to by the result of aneuploidy (2n + 1) in the hybrids under study. Aneuploidy was revealed for the chromosomes I, III, IX, XII. Disomic clones of 15B-P4 strain were unstable.     

A strain of Chaetomium olivaceum

A strain ofChaetomium isolated from the aerial plant parts of Polish-type rape has been tentatively classified asC. olivaceum. Frequentin situ germination of perithecial hair and their occasional branching was shown. A re-evaluation of the use-fulness of characters of perithecial hair and development of other taxonomic concepts in the genusChaetomium is advocated.Contribution, Alberta Department of Agriculture, Plant Industry Laboratory, Edmonton, Alberta.     

小麦——黑麦染色体易位系的细胞学鉴定

用C－带技术分析了普通小麦“中国春”、黑麦“胜利”及小黑麦与普通小麦经辐射处理的后代中产生的并经多代纯化的5个带有黑麦某些性状的普通小麦品系的根尖染色体,结果表明：品系98－5－1为1A／1R纯合易位系,具有抗锈病、抗白粉病等基因,可作为诱导小片段易位的资源。作者提出在小麦－黑麦易位系鉴定中应用更高分辩率的G－带技术识别黑麦染色体片段或小片段易位。     

伞形酮产生菌的构建

【背景】伞形酮为香豆素类化合物,具有较广泛的药用价值,也是重要的工业制品原料。传统的植物提取成本较高,应开发更有效的获取技术。【目的】利用微生物为宿主异源合成伞形酮。【方法】对不同植物来源香豆素类化合物合成基因进行整合;以酿酒酵母为宿主,通过对宿主酪氨酸代谢通路的改造构建表达宿主,进一步将表达基因转化到改造后的宿主中。【结果】获得产伞形酮的酵母菌株,产量为(67.39±4.87)μg/mL。【结论】通过整合生物合成基因可获得香豆素类天然产物表达菌株。     

A polydactylous strain of mice

Summary A highly inbred strain ofMus musculus is described in which 12% of the males and 18% of the females are polydactylous. This polydactyly is the only abnormality occurring in these mice. In most cases only the first digit (big toe) of the right hind foot is more or less duplicated, but the left foot and other toes may also be affected. Abnormal fathers transmit the peculiarity more often to their daughters than to their sons. This fact cannot be explained on a genetic basis, since for various reasons genetic differences between these mice cannot be assumed to exist. In general, polydactylous mice have an excess number of motor neurons innervating the foot in the spinal cord on the abnormal side. This may be the cause for polydactyly as is known to be inAmphibia.     

Laccase production by a monokaryotic strain of Pycnoporus cinnabarinus derived from a dikaryotic strain

Monokaryotic Pycnoporus cinnabarinus strains were obtained from the dikaryotic strain I-938. One of these, designated MK18, consistently produced high laccase activity. In cultures of MK18 and I-938 where ferulic acid was added as laccase inducer, laccase activity was enhanced about 2.5-fold reaching 3400 U/l for the MK18 strain. Laccase was purified to homogeneity and under the selected growth conditions, only one isoform of the enzyme was produced. The N-terminal sequence was similar to the amino terminal sequence of laccase II from Trametes versicolor. The enzyme was stable at 60 C for more than 1 h.     

Toxicity of chlorobenzene on Pseudomonas sp. strain RHO1, a chlorobenzene-degrading strain

Pseudomonas sp. strain RHO1 able to use chloro- and 1,4-dichlorobenzene as growth substrates was tested towards sensitivity against chlorobenzene. Concentrations of chlorobenzene higher than 3.5 mM were found to be toxic to cells independent of pregrowth with chlorobenzene or nutrient broth. Below this concentration, sensitivity towards chlorobenzene depended on the precultivation of the cells, i.e. type of growth substrate (chlorobenzene or nutrient broth) and the concentration of chlorobenzene as the growth substrate. Cells grown in continuous culture were especially sensitive with a threshold concentration of 2.5 mM chlorobenzene. In addition to chlorobenzene, metabolites also seem to function as toxic compounds. 2-Chlorophenol and 3-chlorocatechol were isolated from cell extracts. Cleavage of 3-chlorocatechol by catechol 1,2-dioxygenase seems to be the critical step in the metabolism of chlorobenzene.