Levan production using mutant strains of Zymomonas mobilis in different culture conditions

Several levan hyperproducing mutants of Zymomonas mobilis strains were selected by mutagenesis with N-methyl-N-nitro-nitrosoguanidine and caffeine. Highest levan production (41 g l^–1) was obtained with a mutant strain HL 29 in a culture medium containing 200 g sucrose l^–1 and 0.5 g (NH₄)₂SO₄ l^–1 stored at 7 °C for 29 days. This is the first report describing the levan synthesis by Z. mobilis at 7 °C.     

Enhancement of Secretion and Extracellular Stability of Staphylokinase in Bacillus subtilis by wprA Gene Disruption

Staphylokinase (SAK), a polypeptide secreted by Staphylococcus aureus, is a plasminogen activator with a therapeutic potential in thrombosis diseases. A Bacillus subtilis strain which is multiply deficient in exoproteases was transformed by an expression plasmid carrying a promoter and a signal sequence of subtilisin fused in frame with the sak open reading frame. However, the amount of SAK secretion was marginal (45 mg/liter). In contrast, disruption of the wprA gene, which encodes a subtilisin-type protease, strongly promoted the production of SAK in the stationary phase (181 mg/liter). In addition, the extracellular stability of mature SAK was dramatically enhanced. These data indicate a significant role of the wprA gene product in degrading foreign proteins, both during secretion and in the extracellular milieu.     

Production of Poly(3-Hydroxybutyrate) by Fed-Batch Culture of Recombinant Escherichia coli with a Highly Concentrated Whey Solution

Fermentation strategies for the production of poly(3-hydroxybutyrate) (PHB) from whey by recombinant Escherichia coli strain CGSC 4401 harboring the Alcaligenes latus polyhydroxyalkanoate (PHA) biosynthesis genes were developed. The pH-stat fed-batch cultures of E. coli CGSC 4401 harboring pJC4, a stable plasmid containing the A. latus PHA biosynthesis genes, were carried out with a concentrated whey solution containing 280 g of lactose equivalent per liter. Final cell and PHB concentrations of 119.5 and 96.2 g/liter, respectively, were obtained in 37.5 h, which resulted in PHB productivity of 2.57 g/liter/h.     

Functional studies on sciatic nerve blood flow in respect to its vascular supply and tonic neural activity.

An introduction of laser flow meters for a continuous measurements of a tissue blood flow has opened new avenues for an accurate assessment blood flow in peripheral nerves. The aim of our study was: 1) to carry out a functional verification of anatomical sources of a sciatic nerve blood supply in the rat; 2) develop a measurement technique to facilitate standardisation of results; 3) to determine the role of nerve fibres tonic activity in the maintenance of a resting blood flow in the sciatic nerve. Based on results of the present study the following conclusions have been drawn out: 1) in order to obtain a real values of the blood flow through the sciatic nerve it is necessary to remove its muscular fascia; 2) an uninjured epineurium plays a crucial role in maintaining the resting blood flow; 3) major blood supply of sciatic nerve comes from inferior gluteal and popliteal arteries; 4) the tonic neural activity plays a role in the maintenance of the resting sciatic nerve blood flow in anaesthetised rats.     

Humoral response of the immunologic secretory system of the small intestine in children infected with Giardia intestinalis

Local humoral response of the intestinal mucosa was determined with secretory IgA levels and secretory component activity in enterocytes and duodenal content of 15 children infected with G. intestinalis. The obtained results were compared to those in 5 children with coeliac disease and 12 children with diarrhoea without lambliasis. Secretory IgA was increased in about 50% of children with lambliasis (in the remaining groups in 25% of children) to the values higher than that in the comparative groups. Secretory component activity was relatively high in the intestinal epithelium. Secretory component activity in the duodenal content was high in about 40% of children independently of the examined group. No correlation between the said variables was noted except positive correlation of secretory IgA levels and secretory component activity in the bile.     

Relationships between foliar carbon isotope discrimination with potassium concentration and ash content of the riparian plants in the extreme arid region of China

Carbon isotope discrimination (Δ) has been proposed as an indirect estimation criterion for water use efficiency in C₃ plants. Because of the higher cost for Δ analysis, ash content or K concentration has been proposed as an alternative criterion for Δ in many species. In five typical habitats of the extreme arid Ejina desert oasis in northwest of China, the seasonal variations of foliar δ, ash content, and potassium (K) concentration were researched in two constructive desert riparian plants (Populus euphratica Olivier, Tamarix ramosissima Ledeb). The correlations of foliar Δ with ash content and K concentration in both species were also examined to evaluate the feasibility of the foliar ash content and K concentration as surrogates of Δ in P. euphratica and T. ramosissima. Results showed that there were significant effects of plant species, habitats and growth season on foliar Δ, ash content, and K concentration. Foliar Δ and K concentration in P. euphratica were significantly higher than those in T. ramosissima, whereas, the ash content was reverse. Among habitats, the trends of δ signatures in both P. euphratica and T. ramosissima were similar, δ values and ash content in both species were the lowest in the dune. Both in the Gobi and dune sites, K concentration in P. euphratica and T. ramosissima was different. In the whole growth period, foliar Δ values and ash content in both species were gradually increased, but K concentration was decreased. Ash content was significantly and positively related to δ in both P. euphratica and T. ramosissima. However, significantly negative correlations between foliar δ and K concentration as well as between ash content and K in P. euphratica were found. In T. ramosissima, the relationship was positive but very weak.     

Different Degrees of Plant Invasion Significantly Affect the Richness of the Soil Fungal Community

Several studies have shown that soil microorganisms play a key role in the success of plant invasion. Thus, ecologists have become increasingly interested in understanding the ecological effects of biological invasion on soil microbial communities given continuing increase in the effects of invasive plants on native ecosystems. This paper aims to provide a relatively complete depiction of the characteristics of soil microbial communities under different degrees of plant invasion. Rhizospheric soils of the notorious invasive plant Wedelia trilobata with different degrees of invasion (uninvaded, low-degree, and high-degree using its coverage in the invaded ecosystems) were collected from five discrete areas in Hainan Province, P. R. China. Soil physicochemical properties and community structure of soil microorganisms were assessed. Low degrees of W. trilobata invasion significantly increased soil pH values whereas high degrees of invasion did not significantly affected soil pH values. Moreover, the degree of W. trilobata invasion exerted significant effects on soil Ca concentration but did not significantly change other indices of soil physicochemical properties. Low and high degrees of W. trilobata invasion increased the richness of the soil fungal community but did not pose obvious effects on the soil bacterial community. W. trilobata invasion also exerted obvious effects on the community structure of soil microorganisms that take part in soil nitrogen cycling. These changes in soil physicochemical properties and community structure of soil microbial communities mediated by different degrees of W. trilobata invasion may present significant functions in further facilitating the invasion process.     

Fluorescence fingerprints of oral bacteria

The rapid detection and identification of microorganisms is one of the most important factors in many cases of ill health. The purpose of this study was to determine the fluorescence characteristics of seven oral bacteria using emission spectra with the aim of distinguishing between the bacteria, and to compare fluorescence imaging methods for the direct assessment of oral bacteria. Fluorescence images of each bacterium were obtained under a 405‐nm light source using a two‐filter system. The emissions of all samples were measured with a fluorescence spectrometer. The complete fluorescence data set collected for each sample employed a three‐dimensional data cube. The differences in the autofluorescence characteristics of the seven oral bacteria were determined by principal components analysis (PCA). The fluorescence images of the oral bacteria varied with the genus and the filter system. The three‐dimensional excitation‐emission matrix fluorescence spectra exhibited distinctive fluorescence features associated with intracellular fluorophores. The seven bacteria could be clearly differentiated on the PCA score plot. The findings of this study indicate that oral bacteria can be identified based on their autofluorescence characteristics. Fluorescence spectroscopy coupled with PCA can be used to detect and classify oral bacteria.      

Separation of a bradykinin-releasing enzyme from the proteolytic complex of Levantine viper venom

Two serine hydrolases have been separated from the proteolytic complex of the venom of Levantine viper, Vipera lebetina turanica. The enzyme with mol. weight of 50,000 +/- 5,000, pH-optimum of 8.5 and isoelectric point in the range of 5.6--6.6 had proteolytic activity against casein and hydrolyzed benzoyl-arginine p-nitroanilide. The other enzyme with mol. weight of 37,000 +/- 2,000, pH optimum of 9 and isoelectric point in the range of 4.1--4.5 had no effect on benzoylarginine p-nitroanilide, casein or hemoglobin, but possessed a bradykinin-releasing activity. Both enzymes were stereoselective against L-arginine, hydrolyzing tosyl-L-arginine methyl ester without having any effect on D-arginine ester. The interaction of the enzymes with a number of N(alpha)-arylsulfonylarginine methyl esters has been studied. The influence of the substitute X in the arylsulfonyl part of the substrates upon their hydrolysis by the bradykinin-releasing enzyme has been described by the Hammett equation of rho omicron = 1.14 +/- 0.33 (r = 0.974).     

Sensitivity of apple seed germination to light and some growth regulators

Experiments were aimed at checking whether the non-stratified apple embryos are sensitive to growth factors and light. The effect of growth regulators on light sensitivity was also studied. The stimulating or inhibiting effect of GA3, benzyladenine and IAA or coumarin on the dynamics of apple embryo germination was demonstrated. Seasonal fluctuations of the effect of the growth factors were noted. The stimulating effect of light on the germination of non-stratified apple embryos was demonstrated. This effect is independent of season and seems to be independent of the effects of growth regulators.