Abstract:[Objective] A thermophilic hydrocarbon-degrading strain DM-2, isolated from Shengli oilfield and identified as Geobacillus stearothermophilus, produced an extracellular bio-emulsifier. [Methods] To characterize the bio-emulsifier, its chemical composition was determined by colorimetric method, infrared spectroscopy, HPLC and amino acid automatic analyzer. [Results] The bio-emulsifier is consisted of polysaccharides (71.4%, W/W) and polypeptide (27.75%, W/W). It could emulsify diesel, benzene, xylene and kerosene. It tolarated high temperature, salt and pH. [Conclusion] The bio-emulsifier produced by strain DM-2 is a novel bio-emulsifier and has potential applications in the oil exploitation, oil recovery and transportation, oil tank cleaning, and oil pollution regulation.

Abstract:[Objective] Construction of highly efficient xylose-utilizing Saccharomyces cerevisiae strains by single, double or multiple overexpression of genes involved in the non-oxidative pentose phosphate (PP) pathway. [Methods] TAL1, TKL1, RPE1 and RKI1 under the control of different strong promoters were integrated either alone or in combination into the xyloses-fermenting recombinant yeast strain AYHNEW2. The fermentation performances of the resulting strains were studied on 5% xylose. [Results] The recombinant strains generated with our approach showed improved xylose fermentation performance with varying degrees. The best results were obtained by simultaneous overexpression of all the non-oxidative PP pathway genes, and compared to the reference strain AYHNEW2, the strain resulted from this genetic modification showed a 39.25% and 12.57% increase in ethanol productivity and yield, respectively. [Conclusion] Previous studies for enhancing xylose fermentation rate by genetic modification of the non-oxidative PP pathway had been more focused on overexpression of the individual genes in the pathway. In this work, we demonstrated that, compared to single or partial over-expression of the non-oxidative PP pathway, simultaneous overexpression of all the genes in the pathway was more effective in increasing the rate of carbon flow from xylose to ethanol.

Abstract:[Objective] To identify and classify the Fraxinus sogdianaBunge witches′ broom phytoplasma. [Methods] Horizontal slices of tender stem from Fraxinus sogdianaBunge were stained with aniline blue and 4,6-diamidino-2-phenylindole (DAPI), and then observed under flurescence microscopy. 16S rRNA gene sequences were amplified using direct-PCR and nested-PCR with universal primers P1/P7 and R16F2n/R16R2 for phytoplasmal 16S rRNA gene sequence. Amplicons were analyzed by restriction fragment length polymorphism (RFLP) and a phylogenetic tree was constructed based on the sequences of 16S rRNA gene. [Results] A phytoplasma was identified from Fraxinus sogdianaBunge which with symptoms of witches’ broom and was tentatively named as Fraxinus sogdianaBunge witches’ broom phytoplasma (Fraxinus sogdianaBunge WB). The 16S rRNA gene sequence was deposited in GenBank with the accession number of KF061042. Its RFLP patterns of 16S rRNA gene were the same as jujube witches′ broom phytoplasma which belong to 16Sr V-B subgroup, and it had the same phylogenetic position with jujube witches’ broom phytoplasma strain AB052876. [Conclusion] Fraxinus sogdianaBunge witches′ broom phytoplasma was identified as the member of 16Sr V-B subgroup.

Abstract:[Objective] To study the anti-tumor activity of L-asparaginase II (ASP) of Escherichia coli Nissle1917. [Methods] L-AsparaginaseⅡ gene was amplified from the genome of E. coli Nissle1917 and inserted on the expression vector pET28a. The final expression vector pET28a-asp was transformed into E. coli BL21(DE3) for ASP expression. SDS-PAGE and LC-MS were used to determine the correct expression of ASP. After purification by nickel-affinity chromatography, the recombinant ASP was used to treat mouse 4T1 breast tumor cells, Hep-3B human hepatoma cells and Human Umbilical Vein Endothelial Cells (HUVEC). [Results] L-AsparaginaseⅡgene from E. coli Nissle1917 was successfully expressed in E. coli BL21(DE3) and identified by LC-MS. The purified L-asparaginaseⅡinhibited the growth of 4T1 and Hep-3B tumor cells while not HUVEC. [Conclusion] The L-asparaginaseⅡ of E. coli Nissle1917 was active on 4T1 and Hep-3B tumor cells while not on normal tissue cells. Our results will be helpful for the further study on the active mechanism of ASP and its application in solid tumors therapy.

Abstract:[Objective] Identification of a symbiotic fungus of bag-cultured Auricularia auricula and preliminary studies on its symbiotic effect. [Methods] After purified the symbiotic fungus strain, it was identified by morphology and molecular biological analysis. The symbiotic fungus was inoculated at different stages of bag-cultured A. auricula to explain the relationship between the two fungi. The nutritional analysis of fruit bodies of A. auricula to explore the influence of the symbiotic fungus on nutritional structure of fruit bodies of A. auricula. [Results] The symbiotic fungus strain B-1 was identified as Lasiodiplodia theobromae. The inoculation experiment confirmed that the partial symbiosis between the A. auricula and strain B-1. The nutrition components of fruit bodies of A. auricula analysis found that it changed significantly in the case of the presence of strain B-1, and no obvious changed in morphology. [Conclusion] A. auricula and L. theobromae strain B-1 have the relationship of partial symbiosis, which is first report.

Abstract:[Objective] The aim of this paper was to obtain a bacterial strain which has the ability of degrading mineral phosphorus, potassium and silicon, controlling plant disease, and fixing nitrogen. [Methods] Soil was collected from rhizosphere of soybean (Glycine max), then selected medium supplemented with potash feldspar was used to enrich bacterial strains exhibiting ability of degrading silicate. Dual-culture plate method was used to gain a bacterium which had the strongest ability of antifungal activity to the soybean root rot pathogen Fusarium oxysporum. After that, the activity of degrading mineral potassium, silicon, and phosphorus of the bacterium was tested by shake flask method, meanwhile the optimized Ashby’s medium was used to test the activity of fixing nitrogen. The isolated strain was identified through morphology observation, physiological and biochemical tests and 16S rRNA gene sequence analysis. [Results] A bacteria strain named NK3-4 was isolated from rhizosphere soil of healthy soybean in field. The bacterium inhibited F. oxysporum growth with inhibiting belt of 8.0 mm width on plate. The concentration of dissoluble potassium in medium contained potash feldspar was 15.0 mg/L higher than that in medium without potash feldspar, and the concentration of dissoluble silicon was 131.7% higher than the un-inoculated control after cultivation for 24 hours. The concentration of dissoluble phosphorus was 4.8 times of the un-inoculated control in medium with calcium phosphate as only phosphoric source after cultivation for 8 days. The concentration of dissoluble nitrogen was 4.6 times of the uninoculated control in Ashby’s medium after cultivation for 15 days, and the nitrogen content fixed in the bacterial organism was 12.7 mg in one liter of medium. The identification showed that the NK3-4 strain was a new strain belongs to Paenibacillus terrae. [Conclusion] Strain NK3-4 is a new strain of P. terrae with multifunctions, it can be used as a potential microorganism for exploit of biofungicide and biofertilizer.

Abstract:[Objective] Exoglucanases is a class of cellulase which could degradation crystalline cellulose. Nowadays, how to improve the exoglucanase activity is of importance. [Methods] In this study, strain ASP-524, possessing higher level of cellobiohydrolase, was identified as Aspergillus niger. The cbhB gene was cloned from strain ASP-524, and expressed in Pichia pastoris GS115. [Results] After the induction of 1% methanol for 5 d, the expression strain reached a cellulase activity of 4.74 U/mL. The recombinant exoglucanase was a 57 kD protein with an optimum catalytic activity at pH 5.0 and 50 °C. [Conclusion] The enzyme was stable. The recombinant exoglucanase was relatively stable in a broad pH range, from 4.0 to 6.0, and retained 80% activity.

Abstract:[Objective] The study was conducted to clone avian beta-defensin1 (AvBD1) gene from pigeon tissues, expression of recombinant AvBD1 protein in Escherichia coli and determine its biological characteristics. [Methods] The AvBD1 gene was amplified from bone marrow of pigeon by RT-PCR, differential mRNA expression of this gene was evaluated by real-time PCR. The cDNA of pigeon AvBD1 was sub-cloned into EcoR I and Xho I sites of pProEX-HTa vector to construct recombinant plasmid pProEX-pigeon AvBD1, the recombinant plasmid was expressed into E. coli, the bacteria induced with IPTG. The recombinant protein was purified, antimicrobial activity, physio-chemical characteristics of the recombinant protein were measured by colony counting assays in vitro. [Results] Sequence analysis showed that the cDNA of pigeon AvBD1 consisted of 198 bp nucleotide, encoding a polypeptide of 65 amino acids. Homology analysis showed that pigeon AvBD1 shared the highest percentage of amino acid homology (81.5%) with duck AvBD1. The mRNA was widely expressed in immune system and digestive system. It was demonstrated by Tricine-SDS-PAGE that a 8.8 kD protein which was equal to pigeon pProEX-HTa AvBD1 protein in molecular weight was expressed. The purified recombinant pigeon AvBD1 exhibit extensive antimicrobial activity. In high salt ions conditions, the antibacterial activity was significantly decreased. In addition, little hemolysis of erythrocytes was observed at any concentration of the peptide. [Conclusion] The pigeon AvBD1 gene was successfully cloned from bone marrow, the mRNA was widely expressed in immune system and digestive system. The recombinant protein exhibit extensive antimicrobial activity, has little hemolytic properties. High salt concentration significantly decreased its antibacterial activity.

Abstract:[Objective] To establish and apply an high-throughput assay for screening inhibitors of Mycobacterium tuberculosis protein kinase B (PknB). [Methods] The kinase domain of Mycobacterium tuberculosis PknB was first cloned and expressed in Escherichia coli. The purified protein is utilized for a high-throughput assay for screening PknB inhibitor. [Results] Eight out of 18 000 compounds were identified as exhibiting inhibitory effect upon PknB activity using the screening assay, among which three compounds showed antibacterial activity against Mycobacterium tuberculosis, Mycobacterium marinum and Mycobacterium smegmatis. [Conclusion] The high-throughput screening model has advantages of high sensitivity and stability, which can be used in anti-TB drug screening. Three compounds are worth further study because of their great activities against both PknB and bacterial growth.

Abstract:[Objective] High fermentation efficiency is desirable for Saccharomyces cerevisiae used in the Chinese rice wine brewing. In this study, we developed a drug resistance screening protocol to obtain a Chinese rice wine yeast strain with higher fermentation efficiency. [Methods] Clotrimazole (CTZ)-resistant strains of S. cerevisiae were isolated from the parent Chinese rice wine yeast strain. Then fermentation power, fermentation rate, and brewing property were used to screen mutants with higher fermentation efficiency compared with the parent. [Results] A total of 18 stable CTZ-resistant mutants were obtained through UV mutagenesis from Chinese rice wine yeast strain XY. In these 18 CTZ-resistant mutants, strain XY-3 gave a 5.21% higher max-fermentation rate than that of the strain XY by flask fermentation tests. In lab-scale Chinese rice wine brewing, strain XY-3 (15.30 g/d) also showed a higher maximum fermentation rate than that of strain XY (14.77 g/d), leading to shorter fermentation period of Chinese rice wine brewing by 1–2 days. [Conclusion] Combining traditional mutation with CTZ-resistant screening protocol was an efficient approach to screen Chinese rice wine yeasts with higher fermentation efficiency.

Abstract:[Objective] Investigating the diversity of the cultivable bacteria in marine sediment environments. [Methods] Twenty sediment samples collected from South China Sea were used for bacterial diversity research by using the culture dependent method and 16S rRNA gene sequencing. [Results] Total of 200 strains were obtained, which belong to 47 genera and 99 species and spread in four phyla: Firmicutes, Proteobacteria, Actinobacteria and Bacteroidetes. The predominant group is phylum Firmicutes, in which genus Bacillus takes a great proportion of 55.6%. A few strains in phyla Actinobacteria and Bacteroidetes were also obtained. Eight potential new species and 3 potential new genera were discovered in phyla Firmicutes and Actinobacteria. [Conclusion] The preliminary study indicates that genus Bacillus is the dominant group in sediment environments of South China Sea and bacterial diversity showed a decreasing trend with the increase of sampling depth. Sampling depth maybe is one of the important factors to influence the distribution of bacteria. Diversity of bacteria and novel bio-resources in the sediment environments are very abundant and need to be further researched. Isolating methods and isolation media are the crucial factors to recover the microorganisms inhabiting the sediment environments.

Abstract:[Objective] Lactobacillus plantarum, L. rhamnosus, L. acidophilus and L. delbrueckii, which were widely used in microbial fertilizers, were indistinguishable from each other just by phenotypic characteristics. Rapid identification of the lactic acid bacteria by specific PCR was necessary for detection and ecological evaluation of microbial fertilizers. [Methods] In this study, based on recA and gyrB genes, four pairs of species-specific primers were designed, and the corresponding specific PCR methods were established. [Results] Forty reference strains belonging to seven genera, such as Lactobacillus, Lactococcus, Pediococcu, Bacillus, Paenibacillus, Brevibacillus and Pseudomonas, were tested. The results showed that, the target single band was consistently amplified from only the 4 strains of lactic acid bacteria. Meanwhile, sixteen strains of lactic acid bacteria from microbial fertilizer products were identified by this specific PCR, the results were consistent with that of 16S rDNA sequence analysis and Biolog. [Conclusion] The methods of specific PCR were species-specific and effective, and could be used in the rapid identification of L. plantarum, L. rhamnosus, L. acidophilus and L. delbrueckii. The results will provide technical supports for the detection and ecological evaluation of microbial fertilizer.

Abstract:[Objective] This study was to isolate a tylosin-degrading strain from the soil deposited by tylosin pharmaceutical waste and investigated its degradation characteristics. [Methods] The strain was identified based on the morphology observation, experimental results of physiology and biochemsitry, and then the identification and phylogenetic analysis of the isolated strain was performed by 16S rRNA gene sequence, also, the characteristics of the strain in degradation of tylosin was investigated. [Results] A strian named TS1 was newly isolated from the soil deposited by tylosin pharmaceutical waste. The cells of the isolate were Gram-negative rods and the colony morphology was round, oyster white, opaque, and smooth with regular edge. The isolate was identified as Burkholderia vietnamiensis. This strain was capable of degrading 99% of tylosin in medium with an initial concentration of 300 mg/L after 72 h of incubation under conditions of the initial pH 7.0 and 35 °C. [Conclusion] The isolated strain has a high ability to degrade tylosin, and may be used for bioremediation of environment contaminated by solid or liquid waste containing tylosin residue.

Abstract:[Objective] The aim of this study was to uncover the diversity of actinobacteria associated with corals Porites lutea and Galaxea fascicularis. [Methods] Total DNA of coral samples was extracted for PCR amplification with the primers of class actinobacteria. Two clone libraries were constructed for P. lutea and G. fascicularis coral samples. We carried out phylogenetic and statistic analysis based on 16S rRNA gene sequences in order to investigate the communities of actinobacteria associated with corals P. lutea and G. fascicularis. [Results] One hundred and eighteen clones of the P. lutea library were sequenced. They were classified into 58 OTUs, which distributed in suborders Acidimicrobineae, Corynebacterineae, Micrococcineae, Propionibacterineae and unclassified groups. Ninety-six clone sequences were retrieved from G. fascicularis library. They were classified into 31 OTUs, which were distributed in Acidimicrobineae and unclassified groups. Results of diversity index and rarefaction curve analysis suggested that coral P. lutea harbored more diverse actinobacteria than G. fascicularis. [Conclusion] Actinobacteria associated with corals P. lutea and G. fascicularis showed a high level of diversity. There were a large number of unknown Actinobacteria taxa in this environment.

Abstract:Stable isotope probing (SIP) is a series of techniques by combining stable isotope labeling with molecular methods. SIP links microbial function and interactions with identity without isolated culture, which avoids the drawback of pure culture and extends the available boundary of microbial resources. The application of SIP to identify functional microorganisms in organic pollutant biodegradation has a bright prospect. This review introduces the fundamental principal and procedure of SIP, the characteristic of PLFA-SIP, DNA-SIP and RNA-SIP, and the application of SIP in biodegrading organic pollutants (Benzene, Toluene, Ethylbenzene and Xylene (BTEX); Polycyclic aromatic hydrocarbons (PAHs); Polychlorinated biphenyls (PCBs)). Future prospect of SIP in rhizospheric biodegradation is also presented.

Abstract:G protein is located in the hub of the cellular signal transduction network, important in regulating the activity of G-protein. Regulators of G protein signaling (RGS) primarily function as GTPase-accelerating proteins (GAPs) that promote GTP hydrolysis by the Gα subunits, thereby inactivating the G protein and rapidly switching off G protein-coupled signaling pathways. Since the first RGS protein was identified from the budding yeast Saccharomyces cerevisiae, more than 30 RGS proteins have been characterized from several typical fungi, such as Aspergillus nidulans, Metarhizium anisopliae, Magnaporthe oryzae, Gibberella zeae, Fusarium verticillioides, Cryptococcus neoformans and Candida albicans. RGS proteins play pivotal roles in fungi including vegetative growth, sporulation, mycotoxin/pigment production, pathogenicity and mating. In this review, the functions of RGS proteins in different fungi were summarized, and the functional domains and regulation mechanism of RGS proteins in fungi were discussed.

Abstract:We developed a novel method to construct mutagenesis libraries via in situ error-prone PCR. One of our recent PCT patents described a novel method that adding a ligation step mediated by thermostable Thermotoga maritima (Tma) DNA ligase to form the repeated PCR cycles of “denaturation–annealing–elongation–ligation”, which allows exponential amplification of circular DNA. In this method, circular PCR products are generated by using a long dsDNA primer pair, which is designed to carry a selection marker different from the original selection marker of the template plasmid, the template plasmid carrying the original marker is eliminated when transformed host cells are cultured under the new selection pressure. If the product serves as the template for the next round of amplification, accumulation of positive mutations can be obtained by multiple rounds of in situ error-prone PCR. This method has been used to create random mutagenesis libraries of a xylanase gene and a cellulase gene. Screening of these libraries resulted in mutant proteins with desired properties, demonstrating the usefulness of in situ error-prone PCR for creating random mutagenesis libraries for directed evolution.

Abstract:Peroxisome is an organelle with single membrane in various eukaryotic cells, and contains various enzymes essential for multiple physiological and metabolic processes in organisms. At present, more than 30 proteins that control peroxisome assembly, division, and inheritance are identified from fungi, named peroxins (encoded by PEX genes). Peroxins are also involved in glyoxylate cycle and in fatty acid metabolism, and related closely with the pathogenicity of fungi. Recently, peroxins have been identified from increasing number of fungi with the development of genome sequencing technology, as well as the application of novel experimental technology. In this review, we summarized the category and distribution of peroxins, and discussed the properties and functions of peroxins in fungi.

Abstract:Microsporidia are obligate intracellular eukaryotic parasites that infect a wide variety of species, including humans. Members of this phylum have some unusual characteristics compared with other eukaryotes, including the lack of mitochondria, Golgi apparatus, peroxisomes and ?agella, which therefore led to the Archezoa hypothesis, namely the origin of the Microsporidia might have preceded the endosymbiotic origin of those cellular components. However, some recent studies have indicated that Microsporidia related to the fungi and that Microsporidia retain a mitosome which is thought to be the remnant of the mitochondria. The long-branch attraction also explains the primitive placement of Microsporidia within the eukaryotic phylogenetic tree. Here we review the microsporidian taxonomic revisions and discuss the causes and results for these study.

Abstract:Microbiology is an important branch in life sciences, and contributes greatly the development of the other disciplines such as molecular biology. Microbiology Experiment is reassigned as an elective course for the freshmen in Peking University. In order that the students are able to master the basic techniques in microbiology experiment, to have a satisfactory learning result, after the author consults a lot of microbial experimental textbooks used in national and international comprehensive universities, analyzes the relative experiments seriously in the books, then defines the basic experimental microbial teaching requirements and aims: the students are able to grasp the basic experimental techniques and use the techniques to solve the practical problem. According to the teaching aims in the new teaching system, the author redesigns and enriches the experiments, rearranges the teaching in modular pattern to increase the integrity, consistence, practicability and opening of the course, to raise the interests of the students and to achieve the teaching goal.

Abstract:An important mission of teaching-and-research-based university is to develop the students’ scientific innovation and their ability of solving the practical problem. In order to improve the theoretical and practical teaching of the subject Environmental Microbiology, discussion on course contents, teaching method, etc. is made in this paper, which provides a new idea for the curriculum reform of Environmental Microbiology.

Abstract:According to the updating concept of Oral Microbiology, it was reformed on traditional experimental teaching system. We have enhanced experimental contents and innovative design to optimize the teaching system by alternating at the same time of basic experiment, specialized experiment, comprehensive experiment, innovative experiment, and innovate while alternating teaching system, effectively improve the practice of teaching. By teaching reform, we have effectively improved the level of practice teaching.

Abstract:Microbiology, an important basic course of life sciences, features high applicability. In order to achieve the talent training goal of our school, according to characteristic industry of our city and the situation of the course, we took reform measures of Microbiology teaching steps of theory teaching, experiment and practical teaching, and teacher training. They achieved good results.

Abstract:[Objective] This study aims to establish a rapid specific multiplex-PCR detection of Vibrio parahaemolyticus by targeting gyrase, tdh, trh genes simultaneously. [Methods] Three pairs of reported primers were mixed in a single PCR tube. Through optimizing the concentration of primers and anneal temperature, the best reaction condition and primers ratio were determined. This method was validated by specificity test, sensitivity test and comparison test. The PCR-amplified products were analyzed by automatic capillary electrophoresis device. [Results] The predicted DNA amplified bands exhibited at sequences of 91, 269 and 485 bp, indicating high specificity. Assay on sensitivity of cell concentration in pure culture condition showed that the detection limit of amplified gyrase, tdh and trh genes were 6.6×101, 6.6×102 and 6.6×101 CFU/mL respectively. When background interference existed, the detection limit of cell concentration of amplified gyrase, tdh and trh genes were 6.6×103, 6.6×104 and 6.6×103 CFU/mL respectively. The sensitivity experiment for testing genomic DNA template concentration showed that the detection limit was 1.36 μg/L. This method was applied to the test for imported seafood, the results matched the FDA 2004 standard. The amplified bands can be distinguished from each other more easily, comparing with those of FDA 2004 standard. [Conclusion] The multiplex-PCR method was successfully established. It is accurate, rapid and convenient. It can be applied to detect Vibrio parahaemolyticus or pathogenic Vibrio parahaemolyticus with tdh gene or trh gene.

Abstract:[Objective] To establish the epifluorescence microscopic (EFM) method for rapid and reliable enumeration of marine viruses. [Methods] Fixed sea water samples were filtered through 0.02 μm filter, and virus particles were collected on the membrane. After stained with SYBR Green I, viruses were observed and counted under epifluorescence microscope using a grid micrometer. [Results] The EFM method was optimized to count marine viruses rapidly and reliably. [Conclusion] The epifluorence enumeration method was established as well as applied to count marine viruses.

Abstract:[Objective] The real-time PCR, with high specificity and high sensitivity, has been widely applied in quantifying microbial quantity in complex environments. We used this method to quantify TDMTDL (trans-1,10-Dimethyl-trans-9-decalol) producing microbes during the liquor brewing proecss. [Methods] Through the optimization of DNA extraction method for Daqu and fermented grains, we established two real time-PCR standard curves for Daqu and fermented grains respectively. The precision and accuracy of this method were verified. The real-time PCR method was applied to quantify the Streptomyces which produced TDMTDL in Daqu and fermented gains. [Results] The results showed that TDMTDL producing Streptomyces number was 105 orders of magnitude in Daqu and the number was highest in Qingcha among three kinds of Daqu. In the initial stage of fermentation, the microbial number was 104 orders of magnitude. Along with the continuous fermentation, the number of Streptomyces decreased. [Conclusion] Real-time PCR could quantify earthy odor producing Streptomyces in liquor brewing process successfully, this work also had significance of quantify other microbes in liquor brewing process.

Abstract:

Abstract:[Objective] To construct the plcR gene knockout mutant of Streptococcus suis serotype 2 (SS2) highly virulent strain 05ZYH33 and analyze the role of plcR in the pathogenesis of SS2. [Methods] The plcR gene was replaced with a spectinomycin resistance cassette through homologous recombination, then multiple-PCR, RT-PCR, and sequence analysis were performed to identify the knockout strain ?plcR. The effects of plcR deletion on the basic biological characteristics and virulence of SS2 were then determined in this study. [Results] The results of RT-PCR confirmed that 05SSU0241 and 05SSU0242 should be transcribed as a single operon. The isogenic mutant ?plcR was successfully constructed verified by multiple-PCR and RT-PCR. No significant differences in biological characteristics, including growth rate, colony morphology and hemolytic activity, were detected between the two strains. Pathogenic trial in mouse showed that wild-type strain induced high fatality rate as much as 70%, whereas the ?plcR mutant caused a 40% fatality rate. Obviously that the virulence of the ?plcR mutant was attenuated remarkably compared with the wild type. [Conclusion] The plcR gene, a foreign gene exclusively existed in virulent SS2 strains, plays an important role in the pathogenesis of SS2 infection.

Abstract: