Adenylate cyclase activity of Bordetella organisms. I. Its production in liquid medium

Abundant adenylate cyclase activity was found in the phase I cultures not only of Bordetella pertussis but also fo B. parapertussis and B. bronchiseptica. The enzyme activity in the culture fluid increased rapidly and reached a peak during the logarithmic growth phase. B. parapertussis and B. bronchiseptica especially produced a high activity of the enzyme in the culture fluid during the logarithmic phase, but little or no activity was detected in the cells throughout the growth period. In the culture of B. pertussis, the intracellular activity was higher than that in the culture fluid. Phase III cultures of these species lacked both the extracellular and intracellular enzyme activities throughout their growth. In the culture of B. parapertussis, accumulation of cyclic AMP was parallel to that of adenylate cyclase activity through the growth periods, but in B. pertussis there was no parallelism from the stationary through the declining phases. The difference in production patterns of the enzyme activity among the species is discussed.     

Alteration of tyrosine isoaccepting transfer ribonucleic acid species in wild-type and asporogenous strains of Bacillus subtilis.

The relative amounts of two isoacceping species of tyrosine transfer ribonucleic acid, tRNATyrI and tRNATyrII, determined from reversed phase 5 profiles of tyrosyl-tRNA, prepared from Bacillus subtilis strain W168, were growth phase and medium dependent. The growth phase-dependent alterations in the relative amounts of tRNATyr species were also demonstrated in 11 asporogenous strains of B. subtilis. The proportion of tRNA-Tyr species and the extent of the alteration in their relative amounts during the transition from the exponential to the stationary phase of growth of these strains was not directly correlated with the formation of spores by strain W168 grown in various media or the stage at which the asporogenous strains are blocked in the process of sporulation.     

Induction of morphogenesis in the genus Arthrobacter.

Thirty-eight different compounds were used with 17 species of Arthrobacter to determine their ability to support growth and to induce the morphogenic cycle. In most cases, when a compound supported growth, it also induced the rod phase of growth. However, in a few cases, a compound would support growth with cells remaining in the coccoidal phase throughout the growth cycle. Arthrobacter crystallopoietes was unique in the most compounds that supported growth did not induce the rod phase of the morphogenic cycle.     

Triaglycerol metabolism in Saccharomyces cerevisiae. Relation to phospholipid synthesis.

The acylglycerol content of Saccharomyces cerevisiae has been examined during cellular growth. The cells maintained a constant amount of phospholipid and diacylglycerol throughout growth. Triacylglycerol content fell in the early exponential phase of growth and then increased sharply upon entry of the culture into the stationary growth phase. Pulse-chase experiments with [1-14C]oleic acid and [2-3H]- and [1-14C]glycerol indicated that the triacylglycerol molecule was utilized for phospholipid synthesis in early exponential phase probably through a diacylglycerol intermediate. A substantial turnover of phospholipid during growth was also apparent. No role for the triacylglycerol could be found in regulating the fatty acid species of the phospholipid nor in the storage of fatty acid for energy metabolism.     

Biotests with phytoplankton assemblages. Growth limitation along temporal and spatial gradients

The development of eight different species (populations) along temporal and vertical gradients in several lakes was studied. Many populations had an exponential growth phase and a decline phase. The growth rate was often high during the exponential phase. Some species, e.g. Oscillatoria spp. and Synedra cf. acus, often also had a long stationary phase. The growth rate and the sinking rate of these populations were often very low. Laboratory batch experiments with dilute phytoplankton populations were carried out to estimate the degree of growth limitation (L) for different populations sample from different lakes during the three growth phases. L was always low and often zero for populations initially in the exponential phase and always high for populations initially in the decline phase. The biotests also gave results that can help to explain the vertical distribution of Oscillatoria or Asterionella in three lakes investigated. The results indicate that the growth rates and the development of the populations were dependent on the external chemical and physical conditions. The transition between the different growth phases seemed often to be dependent on the external nutrient conditions. P, N, Si and Fe were probably the most growth-limiting nutrients. The growth rate of some diatoms was probably limited directly or indirectly at high pH. Laboratory biotests with natural populations may give valuable information on the growth-properties of different populations in the lakes. The biotests should, however, be carried out in combination with chemical and physical measurements and quantitative determinations of population densities.     

Effects of spatial variation of cells and nutrient and product concentrations coupled with product inhibition on cell growth in a polymer scaffold.

The effects of spatial variation of cells and nutrient and product concentration, in combination with product inhibition in cell growth kinetics on chondrocyte generation in a polymer scaffold, are analyzed. Experimental studies reported previously have demonstrated spatial dependence in the cultivation of chondrocytes. In the present study, the cell-polymer system is assumed to consist of two distinct phases. The cells, fluid, polymer matrix, and extracellular matrix comprise one phase, and the other phase consists of a fluid and polymer matrix. The only two species in the fluid considered to affect cell growth are the nutrient and product. The multiphase transport process of these two species in the cell-polymer system is described by the species continuity equations and corresponding boundary conditions for each individual phase. A volume-averaging approach is utilized for this system to derive averaged species continuity equations for the nutrient and product concentrations. The volume-averaging approach allows for a single species in a two-phase system to be represented by a single averaged continuity equation. Competitive product inhibition, saturation kinetics of substrate, and cell population control are assumed to affect the cell growth kinetics. A modified Contois growth kinetic model is used to represent the three factors that affect cell growth. A parameter analysis is performed and the results are compared qualitatively with experimental data found in the literature.     

太白红杉林斑块结构与群落特征

根据森林循环理论, 森林群落的动态是处于不同发育阶段的镶嵌系统。通过调查太白山亚高山针叶林带太白红杉 (Larix chinensis) 林的结构, 确定出4种斑块阶段 (林窗阶段、建立阶段、成熟阶段和衰退阶段), 研究了森林斑块动态变化和生物多样性变化规律, 并测定分析了不同斑块类型内光照和温度的日变化规律。结果表明:1) 群落内不同斑块类型的比例分别是:林窗阶段40.3%, 建立阶段34.0%, 成熟阶段17.2%, 退化阶段8.5%。2) 不同斑块类型内, 环境因子 (光照和温度等) 的日变化差异明显。其中, 在林窗阶段的光照强度和土壤表面温度要比其他3个阶段变化更大。3) 森林循环过程中, 不同高度和不同径级个体的密度存在着明显差异。4) 平均胸径、高度和平均基面积、个体平均体积和立地材积均随着森林的循环而增加。5) 森林循环过程中, 生物多样性的变化为波形的。运用自然干扰与斑块动态理论, 解释了太白红杉林循环过程中不同斑块之间生物多样性存在差异的可能原因。     

芦芽山林线白杄与华北落叶松径向生长特征比较

分别于2007年7月15日—8月7日和9月5日—10月9日,在山西芦芽山林线附近,应用树木径向变化记录仪测量了6株白杄和5株华北落叶松树干的径向生长过程,同步监测环境因子.结果表明：白杄与华北落叶松在7—8月对环境变化的敏感度无显著性差异,在相对低温干旱的9—10月,白杄对环境的敏感度更高;两树种的净生长曲线和累积变化曲线在7—8月呈上升趋势,9—10月则先下降而后基本保持不变,且白杄生长曲线的波动较大;两树种的茎干变化与水分条件显著相关,其中白杄受大气湿度和温度影响较强,而华北落叶松受土壤水分的影响较强.     

The vertical foliage distributions of six understory tree species in a Chamaecyparis obtusa Endl. forest

Summary The relationships between the amounts of foliage and heights of trees were studied for the dominant understory tree species, including three evergreen and three deciduous species, in a secondary forest of Chamaecyparis obtusa Endl. The relationships showed two phases: leaf increasing and stationary phases. In the leaf-increasing phase, the height growth allowed these species to expand the canopy by increasing the number of leaves. In the stationary phase, the number of leaves was relatively constant number irrespective of tree height from 160 to 400 cm. The number of leaves in the stationary phase represents the maximum number of leaves that can be supported by trees under shady conditions. From the analyses of vertical distributions of leaves in six species, mono- and multi-layer foliage distributions were detected. Two evergreen species, Eurya japonica and Cleyera japonica, showed multi-layer foliage distributions, whereas three deciduous species, Lyonia ovalifolia, Rhododendron reticulatum and Vaccinium hirtum, and one evergreen species, Pieris japonica, showed mono-layer foliage distributions. The relationships between the weights of non-photosynthetic and photosynthetic organs of the six species were examined. The proportion of non-photosynthetic organs increased with tree height. The understory species attained the stationary phase and were maintained by minimizing their investment in non-photosynthetic organs, i.e. their height growth was arrested by the shady conditions under the crown trees.     

Physiological and cultural characteristics ofChromobacterium marinum sp. n.

A new species ofChromobacterium was isolated from open ocean waters. While it possessed somewhat different flagellar characteristics than some described species it demonstrated enough affinities to establish it in the genusChromobacterium. Under optimum conditions this organism had an unusually short generation time as well as an unusually rapid transition from the lag phase of growth to the death phase. It is suggested that this characteristic is one of the major reasons that organisms of this type have not, in the past, been successfully transferred from isolation plates inoculated with samples of sea water. The proposed name isChromobacterium marinum.     

Sequence, regulation, and functions of fis in Salmonella typhimurium.

The fis operon from Salmonella typhimurium has been cloned and sequenced, and the properties of Fis-deficient and Fis-constitutive strains were examined. The overall fis operon organization in S. typhimurium is the same as that in Escherichia coli, with the deduced Fis amino acid sequences being identical between both species. While the open reading frames upstream of fis have diverged slightly, the promoter regions between the two species are also identical between -49 and +94. Fis protein and mRNA levels fluctuated dramatically during the course of growth in batch cultures, peaking at approximately 40,000 dimers per cell in early exponential phase, and were undetectable after growth in stationary phase. fis autoregulation was less effective in S. typhimurium than that in E. coli, which can be correlated with the absence or reduced affinity of several Fis-binding sites in the S. typhimurium fis promoter region. Phenotypes of fis mutants include loss of Hin-mediated DNA inversion, cell filamentation, reduced growth rates in rich medium, and increased lag times when the mutants are subcultured after prolonged growth in stationary phase. On the other hand, cells constitutively expressing Fis exhibited normal logarithmic growth but showed a sharp reduction in survival during stationary phase. During the course of these studies, the sigma 28-dependent promoter within the hin-invertible segment that is responsible for fljB (H2) flagellin synthesis was precisely located.     

THE “PALMELLOID” STATE IN A BLUE-GREEN ALGA,ANABAENA SP. I. PRELIMINARY REPORT

The development of a “palmelloid” phase was studied in an adventive growth of a species of the blue-green alga Anabaena sp. and in culture of the same strain. The primary change from its characteristic filamentous structure was the separation of the cells from one another. This was accompanied by the excessive production of capsular slime in which the separated cells were arranged at random. Associated with this were a gross change in cytology and a change in shape of cell from spheroidal to enlarged ellipsoidal. Fresh culturing of palmelloid cells resulted in the resumption of the typical filamentous growth, which in time reverted to the palmelloid phase.     

The inhibition of bacterial growth by ochratoxin A.

A series of bacterial species was examined for their sensitivity to ochratoxin A. Only grampositive bacteria could be inhibited, generally at a pH lower than 7.0. Bacillus subtilis did not show any reduction of growth rates in presence of ochratoxin A, but had a prolonged lag phase. With Staphylococcus pyogenes var. aureus and Streptococcus faecalis, a prolonged lag phase and a reduction of the growth rate was observed. Most sensitive was Streptococcus faecalis in the exponential-growth phase. The inhibition could be diminished by changing the pH to neutral, or by addition of yeast extract, tetrahydrofolate, or MgSO4. With MgSO4 a complete abolition of the inhibitory effect was achieved, but not with CaCl2. During growth inhibition, protein and RNA synthesis were reduced simultaneously, but not DNA synthesis. Even with the very high concentration of 1 mg/ml, no lethal effect was observed.     

Production of 3-indoleacetic acid by aRhizobium sp. fromMimosa pudica

ARhizobium species isolated from the root nodules of the sensitive plant,Mimosa pudica, produced 60 mg/L of 3-indoleacetic acid (IAA) froml-tryptophan in culture. The production of IAA started simultaneously with the growth and had no different growth or production phase. The stationary phase of growth was reached after 55 h, but the production of IAA increased gradually up to 80 h, and then remained constant. The IAA production could be promoted in the culture medium up to 365% by supplementing the medium with maltose, CuSO₄ and Triton X-100.     

Ion metabolism in a Halobacterium. I. Influence of age of culture on intracellular concentrations

Work is described on the changes in cell ions during growth of cultures of a species of Halobacterium isolated from the Dead Sea. Cell K concentration fell from 5.5 to 3.8 moles per kg cell water during the logarithmic phase of growth and maintained the latter value during the stationary phase (initial medium concentration, 7 mM). Cell Na and Cl followed a complex series of roughly parallel changes. The logarithmic phase ion concentrations were: Na, 1.0–2.3 moles/kg cell water; Cl, 2.3–3.7 moles/kg cell water. The final stationary phase values were: Na, 0.5 moles/kg cell water; Cl, 2.3–2.9 moles/kg cell water (medium NaCl concentration, 3.9 Molal). It is suggested that most of the K⁺ is bound within the cytoplasm.     

Pigmented Plant Tissues in Culture II. Growth, Development and Decline of Chlorophyllous Tissues

During the phase of exponential growth in chlorophyllous calluscultures derived from Haplopappus gracilis, Hypochaeris radicata,and Acer pseudoplatamus, cells double their number on the average,and also their volume, in about 4.3, 6.6, and 9–2 daysrespectively. The two rates decline subsequently but cell expansioncontinues for a short time after division has ceased. With culturesof Oxalis dispar, however, which have an average cell generationtime of about 10 days, there is first a short exponential phasedominated by division, and this is followed by a series of phasesdominated alternately by either division or expansion. Chlorophyll accumulation does not occur in Haplopappus duringthe exponential phase (chlorophyll a decreases) but there isa slow accumulation of caro-tenoids. The bulk of the pigmentsaccumulate during the declining phase of growth mainly afterdivision has ceased. With Hypochaeris and Acer, on the otherhand, accumulation is most intense during the exponential phase,and few pigments are added later. With Oxalis, most of the accumulationoccurs after the exponential phase; carotenoids accumulate untilthe cessation of growth whereas chlorophylls start to declinebefore this. With all species, pigments decline after the cessationof growth. The loss is small in Haplopappus and the tissuesare still bright green when the medium dries out: Hypochaerisand Oxalis, in contrast, eventually become colourless. The data are discussed in relation to the changes in pigmentcontent that accompany the growth and development of a singlecell in each species.     

Effects of cell motility and chemotaxis on microbial population growth.

A mathematical model is developed to elucidate the effects of biophysical transport processes (nutrient diffusion, cell motility, and chemotaxis) along with biochemical reaction processes (cell growth and death, nutrient uptake) upon steady-state bacterial population growth in a finite one-dimensional region. The particular situation considered is that of growth limitation by a nutrient diffusing from an adjacent phase not accessible to the bacteria. It is demonstrated that the cell motility and chemotaxis properties can have great influence on steady-state population size. In fact, motility effects can be as significant as growth kinetic effects, in a manner analogous to diffusion- and reaction-limited regimes in chemically reacting systems. In particular, the following conclusions can be drawn from our analysis for bacterial populations growing at steady-state in a confined, unmixed region: (a) Random motility may lead to decreased population density; (b) chemotaxis can allow increased population density if the chemotactic response is large enough; (c) a species with superior motility properties can outgrow a species with superior growth kinetic properties; (d) motility effects become greater as the size of the confined growth region increases; and (e) motility effects are diminished by significant mass-transfer limitation of the nutrient from the adjacent source phase. The relationships of these results for populations to previous conclusions for individual cells is discussed, and implications for microbial competition are suggested.     

Unusual Growth Phase and Oxygen Tension Regulation of Oxidative Stress Protection Enzymes, Catalase and Superoxide Dismutase, in the Phytopathogen Xanthomonas oryzae pv. oryzae

The enzymes catalase and superoxide dismutase play major roles in protecting phytopathogenic bacteria from oxidative stress. In Xanthomonas species, these enzymes are regulated by both growth phase and oxygen tension. The highest enzyme levels were detected within 1 h of growth. Continued growth resulted in a decline of both enzyme activities. High oxygen tension was an inducing signal for both enzyme activities. An 80,000-Da monofunctional catalase and a manganese superoxide dismutase were the major forms of the enzymes detected at different stages of growth. The unusual regulatory patterns are common among several Xanthomonas strains tested and may be advantageous to Xanthomonas species during the initial stage of plant-microorganism interactions.     

物种丰富度对集群生物量的影响及抽样、互补效应的检验

通过8种甲藻构建不同物种丰富度梯度的集群进行室内一次性培养实验,探讨了集群生物量随物种丰富度的增长模式,运用多因素方差分析检验集群内是否存在抽样效应. 运用超产分析、相对产量之和分析和子集分析方法,检验了集群内的生态位互补效应,并运用分离加性方程法定量分离了抽样与互补效应.结果表明: 集群生物量随物种丰富度呈饱和型上升趋势;集群内存在较强的互补效应;在指数生长期,某些特定物种对集群生物量有显著影响,但在生长稳定期,集群生物量不受个别物种出现与否的影响;在生长稳定期,抽样效应总体上为负,而互补效应与净生物多样性效应则总体为正.