A family 5 β-mannanase from the thermophilic fungus Thielavia arenaria XZ7 with typical thermophilic enzyme features

A novel β-mannanase gene, man5XZ7, was cloned from thermophilic fungus Thielavia arenaria XZ7, and successfully expressed in Pichia pastoris. The gene (1,110 bp) encodes a 369-amino acid polypeptide with a molecular mass of approximately 40.8 kDa. The deduced sequence of Man5XZ7 consists of a putative 17-residue signal peptide and a catalytic module belonging to glycoside hydrolase (GH) family 5, and displays 76 % identity with the experimentally verified GH 5 endo-β-1,4-mannanase from Podospora anserina. Recombinant Man5XZ7 was optimally active at 75 °C and pH?5.0 and exhibited high activity at a wide temperature range (>50.0 % activity at 50–85 °C). Moreover, it had good adaptability to acidic to basic pH (>74.1 % activity at pH?4.0–7.0 and 25.6 % even at pH?9.0) and good stability from pH?3.0 to 10.0. These enzymatic properties showed that Man5XZ7 was a new thermophilic and alkali-tolerant β-mannanase. Further amino acid composition analysis indicated that Man5XZ7 has several characteristic features of thermophilic enzymes.     

枯草芽孢杆菌中一种新型双向启动子的功能鉴定

本研究旨在通过转录组分析预测的方法,由地衣芽孢杆菌中筛选获得一种新型双向启动子,鉴定其启动强度。以已知强组成型启动子pShuttle-09为对照,检测其对克劳氏芽孢杆菌碱性蛋白酶基因的表达活性。成功构建了3种重组碱性蛋白酶表达载体及对应的工程菌株。在新型启动子pLA和其反向启动子pLB调控转录下,克劳氏芽孢杆菌碱性蛋白酶表达活性达到164 U/mL和111 U/mL。结果表明,pLA的启动强度明显高于pShuttle-09和pLB,pLA启动子与pLB启动子均可表达碱性蛋白酶。从而为枯草芽孢杆菌表达系统中异源基因的表达提供一个新的方向,也为原核生物中共同表达两种基因提供了新的思路。     

Competition, predation and interspecific synchrony in cyclic small mammal communities

Although competition and predation are considered to be among the most important biotic processes influencing the distribution and abundance of species in space and time, the relative and interactive roles of these processes in communities comprised of cyclically fluctuating populations of small mammals are not well known. We examined these processes in and among populations of field voles, sibling voles, bank voles and common shrews in western Finland, using spatially replicated trapping data collected four times a year during two vole cycles (1987–1990 and 1997–1999). Populations of the four species exhibited relatively strong interspecific temporal synchrony in their multiannual fluctuations. During peak phases, we observed slight deviations from close temporal synchrony: field vole densities peaked at least two months earlier than those of either sibling voles or bank voles, while densities of common shrews peaked even earlier. The growth rates of all four coexisting small mammal species were best explained by their own current densities. The growth rate of bank vole populations was negatively related to increasing densities of field voles in the increase phase of the vole cycle. Apart from this, no negative effects of interspecific density, direct or delayed, were observed among the vole species. The growth rates of common shrew populations were negatively related to increasing total rodent (including water voles and harvest mice) densities in the peak phase of the vole cycle. Sibling voles appeared not to be competitively superior to field voles on a population level, as neither of these Microtus voles increased disproportionately in abundance as total rodent density increased. We suggest that interspecific competition among the vole species may occur, but only briefly, during the autumn of peak years, when the total available amount of rodent habitat becomes markedly reduced following agricultural practices. Our results nonetheless indicate that interspecific competition is not a strong determinant of the structure of communities comprised of species exhibiting cyclic dynamics. We suggest that external factors, namely predation and shortage of food, limit densities of vole populations below levels where interspecific competition occurs. Common shrews, however, appear to suffer from asymmetric space competition with rodents at peak densities of voles; this may be viewed as a synchronizing effect.     

Identification and characterization of a novel cold-tolerant extracellular protease from Planococcus sp. CGMCC 8088

Extremophiles - A psychrophilic extracellular protease was isolated from the marine bacterium Planococcus sp. M7 found in the deep-sea mud of the Southern Indian Ocean. The mature protease is about...     

PKC刺激与抑制对HeLa细胞G_1/S期进程的影响

蛋白激酶Ｃ（ｐｒｏｔｅｉｎｋｉｎａｓｅＣ,ＰＫＣ）是一类分布广泛的丝氨酸／苏氨酸蛋白激酶,在真核细胞的跨膜信号传递中发挥重要的作用［１］．而细胞周期进程是一个复杂的调控过程,受控于多种磷酸酶与磷酸激酶作用下的中心调控体系［２］．大量报道表明ＰＫＣ信号...     

Spatial synchrony in vole population fluctuations – a field experiment

Three mechanisms have been proposed to induce spatial synchrony in fluctuations of small mammal populations: climate‐related environmental effects, predation and dispersal. We conducted a field experiment in western Finland to evaluate the relative roles of these mechanisms in inducing spatial synchrony among cyclic populations of field voles Microtus agrestis. The study was conducted during the increase and peak phases of a vole population cycle on four agricultural field sites situated 1.5–7.0 km apart. Each field contained two 0.5‐ha fenced enclosures and one 1‐ha unfenced control area. One enclosure per field allowed access by small mustelid predators and the other by avian predators; all enclosures prevented the dispersal of voles. The unfenced control areas allowed access by all predators as well as dispersal by voles. Enclosed vole populations were in a treatment‐wise asynchronous phase before the predator access treatments were applied. The growth rates of all enclosed populations were tightly synchronized during the course of the experiment. Conversely, synchrony both among the unfenced populations and between the fenced and unfenced populations was practically non‐existent. During winter, in the increase phase of the cycle, vole populations in all treatments declined to low densities due to a seasonal effect of winter food depletion. During summer, in the peak year of the vole cycle, all populations fluctuated in synchrony. At this time, both small mustelids and birds of prey appeared to be abundant enough to induce synchrony. Dispersal was identified as a potential contributor to synchronization, but the magnitude of its effects could not be reliably discerned. Our results indicate that no single mechanism can account for the observed patterns of spatial synchrony among cyclic northern vole populations. Rather, spatial synchronization is induced by different mechanisms, namely seasonality and predation, acting successively during different seasons and phases of the vole cycle.     

PCR screening of 3-amino-5-hydroxybenzoic acid synthase gene leads to identification of ansamycins and AHBA-related antibiotic producers in Actinomycetes

Aims:  The 3-amino-5-hydroxybenzoic acid (AHBA) synthase is one of the essential and unique enzymes for AHBA biosynthesis. The possibility of screening for ansamycin or AHBA-related antibiotic-producing strains from Actinomycetes by targeting an AHBA synthase gene was explored.
Methods and Results:  A pair of degenerated primers designed according to the conserved regions of five known AHBA synthases was used to detect AHBA synthase genes within the genomic DNA of Actinomycetes. PCR screening resulted in obtaining 33 AHBA synthase gene-positive strains from 2000 newly isolated Actinomycetes. Phylogenetic analysis of these gene fragments along with those involved in the biosynthesis of structurally determined ansamycins showed that the genes with close phylogenetic relationships might be involved in the biosynthesis of compounds with the same/similar structures. Four strains have been proved to be actual geldanamycin or rifamycin producers by chemical characterization of their fermentation products.
Conclusions:  The results confirmed the feasibility of using the AHBA synthase gene as a probe in polymerase chain reaction (PCR) screening of ansamycin or AHBA-related antibiotic-producing strains.
Significance and Impact of the Study:  The PCR screening of AHBA synthase gene represents a direct and sensitive molecular method for rapid detection of AHBA-related antibiotic-producing strains.