Objective To investigate the effect of gold-plating on Co-Cr alloy used for fabricating denture framework on adhesion of Streptococcus mutans. Methods Sixty pieces of specimens made by Co-Cr alloy were randomly divided into the experimental group and the control group. Each group contained 30 pieces. The tested specimens were plated gold on the surface, while the control group received no treatment. The surface roughness of the two groups was measured by SJ-201. The number of bacteria adhered to the surface was assayed by means of colony forming unit ( CFU) method at adhesion periods of 4h,8h,12h. Finally, the effect of the gold-plated processing on the synthesis of extracellular polysaccharide of S. mutans was determined by measuring the activity of CAT. Results The amount of the microbe attached to the surface of experimental group was significantly decreased compared with that of the control group(P<0. 05). The CAT activity of the microbe in experimental group was also significantly reduced(P<0. 05). Conclusion The gold-plating on Co-Cr alloy could reduce the adhesion of S. mutans and the underlying mechanism might be related to the inhibition of the expression of genes coding for extracellular polysaccharide synthetases such as gtfB.

In natural environments bacteria often adopt a biofilm-growth mode. PotD is a spermidine/putrescine-binding periplasmic protein belonging to polyamine transport system and we have examined its role during biofilm formation and for planktonic growth in Escherichia coli BL21(DE3) strains that either over-express PotD (PotD+), or under-express it (PotDi) and also in a control strain with vector pET26b(+) (PotD0). The three strains displayed similar growth in planktonic growth-mode, but over expression of PotD protein greatly stimulated the formation of biofilms, while less biofilm formed by strain PotDi in comparison to strain PotD0. The expressions of five genes, recA, sfiA, groEL, groES, and gyrA, were increasingly expressed in PotD+ biofilm cells. Thus, PotD is likely to change the rate of polyamine synthesis, which stimulates the expression of SOS genes and biofilm formation.

研究了Pseudomonas putida F1利用单环芳香族化合物以及琥珀酸做碳源时单环芳烃降解相关蛋白质的表达,这对于研究这些芳烃的单一和混合降解有重要意义。利用蛋白组学研究方法,通过比较蛋白表达的双向凝胶电泳（2-DGE）图谱,找出不同碳源条件下生长细胞中差异表达的蛋白质。蛋白质经胰酶消化后,进行基质辅助激光解吸电离飞行时间质谱（Matrix assisted laser desorption/ionization-Time of flight（MALDI-TOF）mass spectrometry）分析。结果表明,尽管该细菌在降解甲苯和乙苯时利用同一个代谢途径,但代谢相关蛋白在微生物利用不同碳源时的表达量有所变化。差异表达蛋白可分为4类,代谢蛋白,转运蛋白,适应性相关蛋白以及其他类型蛋白。

Phytase is widely used as a feed additive in industry. It is important to investigate the thermal stability, optimal pH and temperature and protease resistance of phytases in application. We introduced random mutations in a protease-resistance phytase gene of Penicillium sp. using Mn2+-dITP random mutation method, and identified two mutants 2-28 (T11A, G56E, L65F, Q144H and L151S) and 2-249 (T11A, H37Y, G56E, L65F, Q144H, L151S and N354D) with improved thermal stability and optimal temperature and pH. The mutants retained their high resistance to pepsin. The catalytic activity at 37°C was up to 133.3U and 136.6U per mg protein with broad optimal temperature ranges of 37–55°C and 37–50°C, respectively. After a heat treatment at 100°C for 5min, the two mutant proteins retained about 72.81% and 92.43% of the initial activity, respectively. In addition, the optimal pH of mutant 2-249 was reduced to 4.8. All these improved properties made them more suitable to be used as feed additive in the feed industry than the present commercial phytases. Structure analysis suggested that the replacements of G56E, L65F, Q144H, and L151S improved the thermal stability of the protein by increasing new hydrogen bonds among the adjacent secondary structures. Moreover, the mutation of L151S enhanced the activity in the range of 37–70°C and pH 2.5–7.0 by facilitating the interaction between the substrate and the catalytic centre. The substitution of N354D influenced the pH profile by weakening the bondage with the side chain of D353, which caused a pKa shift of the catalytic centre.

In this paper,we described the structures of quinolones,the mechanisms of quinolone uptake into bacterial cells and how it works to kill bacteria.Since the widespread use of quinolone causes the drug resistance increase gradually,several mechanisms of quinolone resistance have been studied,which refer to chromosomal mutations and kinds of plasmid-mediated quinolone resistance.Those researches provide the basis for the development of new quinolone antibiotics.

In this article, we present a novel protocol, called homologous-restraint polymerase chain reaction (HRPCR), for cloning multiple homologous genes. One of the homologous genes was cloned by consensus-degenerate hybrid oligonucleotide (CODEHOP) polymerase chain reaction (PCR) and sequenced. Primers of HRPCR were designed with 20 to 30 nt inverted to the known gene before the 5' end of the CODEHOP primers. The amplification of the known gene was restricted owing to the loop of the PCR product or the incorrect binding of the primers and the template. As a result, only unknown genes could be cloned. This protocol proved to be simple, rapid, and efficient. We applied this protocol to clone the multiple homologous genes of beta-1,4-N,6-O-diacetylmuramidase from the genomic DNA of Streptomyces griseus.

A novel bioflocculant ZL 5-2 was produced by Agrobacterium sp.M-503.The main component of ZL 5-2,i.e.,a kind of polysaccharide,was detected to be mainly consisting of glucose through chemical composition and TLC analysis.It shows that some metal ions,such as Ca2+,Ba2+,Al3+,Mg2+ and Mn2+ can improve its flocculating ability,with Ca2+ presenting the best effects.The bioflocculant is applied effectively in a pH range of 6-12 and temperature range of 4-121 ℃.ZL 5-2 is not biodegradable by pepsin,trypsin,trichloroacetic acid, α-amylase,cellulase and β-1,4 dextranase.Although β-1,3 dextranase can degrade the polysaccharide component of the ZL 5-2,no significant effect on the flocculating ability of ZL 5-2 is found by all of these glycosidase and other effectors.

A novel lysozyme namedβ-1, 4-N, 6-O-diacetylmuramidase R2 was purified and characterized from Streptomyces griseus. The molecular weight of the enzyme was determined by MALDI-TOF-MS as 23.5 kDa. The N-terminal amino acid sequence was DTSGVQGIDVS-HWQG.Chemical modification ofβ-1, 4-N, 6-O-diacetylmuramidase R2 indicated that sulfhydry1 group and carbamidine of arginine residues are not essential for the activity of the enzyme, but lysine residues and imidazole of histidine residues are essential for the activity. The number of essential tryptophan and carboxyl groups was found that only one tryptophan residue and three carboxyl groups in the active site.

The optimal fermentation medium by Serratia marcesens L15-2 produceing chitinase highly,was composed of 1% chitin,0.3% K_2HPO_4,0.3% KH_2PO_4,0.05% MgSO_4,0.05% CaCl_2,0.001% FeSO_4.After fermentation for 4 days at 37 ℃ and purification,the obtained chitinase was purified and tested by SDS-PAGE.The optimal temperature was 50 ℃ and pH was 6.6 for catalysis by the obtained enzyme.The enzyme was stable below 60 ℃ and under pH 4～10.The enzyme activity was effected on by different metal ions.Its actiaity was enhanced by Ba~(2+),Mn~(2+) and Ca~(2+) and inhibited by Fe~(2+) and Zn~(2+).The chitinase also has an obvious effect on restraining the growth of epiphyte.

Biosorption of Cr(VI) by the novel biosorbent ZL5-2 produced by Agrobacterium sp. was studied and infrared spectra of native, absorbing and desorbing ZL 5-2 were compared. The initial pH was important for biosorption. The optimum effect on Cr(VI) biosorption was acquired within initial pH 0.5 to approximately 1.5, then with the pH increasing, the effect on Cr6+ biosorption was reduced. The biosorption for Cr(VI) was a quick process,only within 10 min 65.4% Cr(VI) is biosorbed, and the biosorption rate was over 90% after 60 min, then all the Cr(VI) was biosorbed after 80 min. The biosorption were fitted with Langmuir and Freundlich isotherm adsorption equations. The absorbed Cr(VI) could be recovered by desorption and the desorption rate reached 13.696% to approximately 67.9%. Progress of biosorption was reversible adsorption and irreversible adsorption simultaneously through infrared spectra analysis, however the reversible adsorption was more important in the biosorption and the adsorption belongs to physics adsorption.

植酸是谷物、豆类和油料等作物中磷和肌醇的主要存贮形式[1],同时对保持机体磷的平衡起着重要的作用.以植酸磷形式存在的磷因单胃动物体内缺乏能分解植酸磷的酶而难以被利用,从而造成许多问题:①磷资源的浪费.一方面饲料中的磷得不到有效利用:另一方面则需加入大量无机磷以满足动物对磷的需求,提高了生产成本[2].②高磷粪便对环境的污染.饲料中85%的植酸磷被动物直接排出体外,使周围的土壤和水受到严重污染[2].此外,植酸磷还是抗营养因子,使得单胃动物不能有效利用营养物质,从而降低了禽畜的生产效益[3].

研究了吸附型生物絮凝剂ZL5-2对印染污水、炼油污水、生物工程发酵液的絮凝作用,并同聚合铝絮凝剂对污水和发酵液的絮凝作用进行了比较.经ZL5-2絮凝作用,炼油污水絮凝率为74.7%,COD去除率为32.4%,BOD去除率为55.4%;印染污水絮凝率为65.8%,COD去除率为49.5%,BOD去除率为62.3%;青霉发酵液和灰色链霉菌发酵液絮凝率最高可分别达到68.4%和69.0%.

Objective: To investigate the effect of RX-17 bacteriolytic enzyme derived from streptomyces griseus on the growth of a cariogenic microbe streptococcus mutans and the development of caries in rats. Methods: Wistar rats were fed with cariogenic forage 2000# and orally infected with streptococcus mutans. The rats were divided into 3 groups and administered with distilled water,sodium fluoride and RX-17 bacteriolytic enzyme, respectively, then the plague pH, germiculted plague bacteria, and obtained jaws were measured for evaluating caries scores by Keyes method. Results: Plague pH of RX-17 bacteriolytic enzyme group was significantly higher than that of distilled water group(P0.05),but lower than that of sodium fluoride group(P0.05). The number of streptococcus mutans was significantly less in RX-17 bacteriolytic enzyme group than in both distilled water group and sodium fluoride group (P0.01 and P0.05). According to Keyes scores, the number of RX-17 bacteriolytic enzyme group at E and DS levels was significantly less than that of distilled water group (P0.01), but had no significant difference with that of the sodium fluoride group(P0.05). Conclusions: RX-17 bacteriolytic enzyme can inhibit the growth of streptococcus mutans and the development of caries, as the sodium fluoride does. RX-17 bacteriolytic enzyme may be used as a novel anti-caries agent.

ABSTRACT Three leuA -like protein-coding sequences were identified in Leptospira interrogans . One of these, the cimA gene, was shown to encode citramalate synthase (EC 4.1.3.-). The other two encoded α-isopropylmalate synthase (EC 4.1.3.12). Expressed in Escherichia coli , the citramalate synthase was purified and characterized. Although its activity was relatively low, it was strictly specific for pyruvate as the keto acid substrate. Unlike the citramalate synthase of the thermophile Methanococcus jannaschii , the L. interrogans enzyme is temperature sensitive but exhibits a much lower K m (0.04 mM) for pyruvate. The reaction product was characterized as ( R )-citramalate, and the proposed β-methyl- d -malate pathway was further confirmed by demonstrating that citraconate was the substrate for the following reaction. This alternative pathway for isoleucine biosynthesis from pyruvate was analyzed both in vitro by assays of leptospiral isopropylmalate isomerase (EC 4.2.1.33) and β-isopropylmalate dehydrogenase (EC 1.1.1.85) in E. coli extracts bearing the corresponding clones and in vivo by complementation of E. coli ilvA , leuC / D , and leuB mutants. Thus, the existence of a leucine-like pathway for isoleucine biosynthesis in L. interrogans under physiological conditions was unequivocally proven. Significant variations in either the enzymatic activities or mRNA levels of the cimA and leuA genes were detected in L. interrogans grown on minimal medium supplemented with different levels of the corresponding amino acids or in cells grown on serum-containing rich medium. The similarity of this metabolic pathway in leptospires and archaea is consistent with the evolutionarily primitive status of the eubacterial spirochetes.

The hairy roots induced by Agrobacterium rhizogenes A 4 were cultured and the effects of different nutrition elements, carbon sources and primary sugar density, hormone as well as temperature and shaker speed were compared. The results showed that when cultured in 1/2B 5 culture with high concentration of initial sucroseand 1mg/L 6 BA and 500mg/L L tryptophan in 28℃and 75r/min, hairy roots grew well and alkaloid production was high.

从灰色链霉菌(Streptomyces griseus)RX-17的发酵液中,通过硫酸铵分级沉淀,CM-Sephadex C-50和CM-Sepharose Fast Flow离子交换层析,纯化得到了溶菌酶R2.该酶分子量约为24.8 kD,等电点约为9.7,N端15个氨基酸的顺序为DTSGVQGIDVSHWQG.R2酶溶解变链球菌Ingbritt(Streptococcus mutans Ingbritt)的最适作用温度为55℃,最适pH为7.0.50℃处理1 h,R2酶残存酶活74%,碱性条件(pH>9)下该酶保持稳定. Zn2+、Cu2+、Fe2+、Cd2+、Pb2+ 可使酶完全失活,螯合剂、盐酸羟胺、溴替丁二酰亚胺及离子型去垢剂SDS抑制R2酶的溶菌作用,而非离子型去垢剂Triton X-100等则能促进溶菌.R2酶溶菌谱广泛,能够溶解多种鸡卵清溶菌酶不能作用的革兰氏阳性菌和革兰氏阴性菌.从对金黄色葡萄球菌(Staphylococcus aureus)的高活性来看,该酶应分类为β-1,4-N,6-O-二乙酰胞壁质酶(β-1,4-N,6-O-diacetylmuramidase).

通过液体及平板溶菌活性测定,证明了灰色链霉菌(Streptomyces griseus)RX-17发酵液中存在对变链球菌(Streptococcus mutans)Ingbritt有强力溶解作用的物质-RX-17溶菌酶.产酶培养基碳、氮源最适配比为蔗糖3%、大豆蛋白胨1.25%、牛肉膏0.2%;最适产酶温度为33℃;高溶氧水平对酶的产生有利.溶菌特异性试验证实了RX-17溶菌酶对金黄色葡萄球菌(Staphylococcus aureus)、乳脂链球菌(S.cremoris)、保加利亚乳杆菌(Lactoba-cillus bulgaricus)、短乳杆菌(L.brevis)、产氨短杆菌(Brevibacterium ammoniagenes)及铜绿假单胞菌(Pseudomonasaeruginosa)等多种G+、G-细菌均有良好的溶解作用.

Bacteriolytic enzyme R1 was purified to electrophoretic homogeneity with the recovery of 6.89% activity by ammonium sulfate precipitation, CM-Sephadex C - 50, CM-Sepharose Fast Flow and Sephadex G-75 chromatography from the culture supernatant of Streptomyces griseus RX-17. The molecular weight and PI of R1 were 16.8 kD and 9.10. The optimal temperature and pH for R1 against Streptococcus mutans Ingbritt were 70 degrees C and 6.6, respectively. Below 50 degrees C and at range pH 6 - 10, R1 was stable. While treated at 60 degrees C for 1 hour, the residual activity was only about 20.3%. Zn2+, Cu2+, Fe2+, Cd2+ and Pb2+ could completely inactivate the enzyme. Chelating agents, hydroxylamine hydrochloriae, Monoiodoacetic acid inhibited the lytic activity against Streptococcus mutans Ingbritt, whereas Mg2+, 2-Mercaptoethanol and some surfactants could stimulate the activity. The enzyme had a broad bacteriolytic spectrum against many G+, G- bacteria which were resistant to egg-white lysozyme. Especially high activity was shown on Streptococcus mutans, Staphylococcus aureus and Lactobaillus.

The results of the orthogonal experiment design showed that the fittest carbon sourse was 3% sucrose and nitrogen was 1.25% soya peptone,025% beef extract for Streptomyces sp.RX-17 produing bacteriolytic enzyme.The study of the optimum cultivation conditions indicated that aeration had singificant effect on the production of the enzyme.The optimum temperature and pH of the lytic activity was 60℃ and 6.0.In alkaline circumstance the enzyme was easy to keep activity.About 36.3% of the original activity remained after 1 hour at 60℃.The lytic activity was very sensitive to the variety of the ionic strength.The enzyme had a broader bacteriolytic spectrum posessing high activity against Streptococcus mutans and Staphylococcus aureus which were resistant to egg-white lysozyme.