Abstract:Abstract: Microbial secondary metabolites play an important role in the field of industry, agriculture, medicine and human health. The molecular regulation of secondary metabolites is gradually becoming noticeable and intriguing. In recent years, many researches have demonstrated that secondary metabolite biosynthesis is tightly linked to the physiological and developmental status in its producer. It is suggested that the biosynthesis of secondary metabolites involves in complex process concerning multi-level regulation. Here we reviewed the recent research progress on the molecular regulation of secondary metabolites in microorganisms. In known about ten thousand kinds of natural secondary metabolites, most of them (about 60%) were produced by Streptomycete. Therefore, the regulation of secondary metabolites in Streptomyces is chosen as the mainline in this review. Additionally, several well-studied antibiotics as the representative members were targeted. Finally, some suggestions, in response to the issues at present, have been presented in this paper.

Abstract:Abstract: Motility was considered to be closely related with biofilm formation positively for a long time because the ability of biofilm formation would be decreased in the motility-defective bacteria. Moreover, the results of defective mutants of flagella and some other regulated proteins suggested that the relationship between motility and biofilm was diverse in different bacteria. Factors other than motility could influence the development of biofilms as well. Namely, motility is not the only determining factor for biofilm formation. Here, we described bacterial biofilm and motility in detail and evaluated their correlation.

Abstract:Abstract: The increase of clinical fungal infection causes a wide awareness. Cryptococcus neoformans is one of the major fungal pathogens. In the past 10 years, much progress has been made in its molecular biological research, including the synthesis and mobilization of the virulence factors as well as the signal transduction pathways during pathogeny. All these will help prevent or treat this fungus. We review the virulence factors and the molecular biological research progress.

Abstract:Abstract : [Objective] To characterize a Bartonella strain M9HN-SHQ from a blood culture of cat from Henan Province, China. [Methods] The organisms were subcultured in 5% CO2 at 37℃ on trypticase soy agar containing 5% sheep blood for 6 to 7 days. We analyzed the isolate using whole-cell fatty acid analysis, Etest for susceptibility testing, random amplified polymorphic DNA(RAPD), pulsed-field gel electrophoresis(PFGE) and sequence analysis of 16S rRNA, gltA, groEL, ftsZ, rpoB, ribC and 16S～23S rRNA intergenic spacer region. [Results] Isolate M9HN-SHQ stained faintly as a gram-negative rod but was easier to visualize when stained by the Giménez technique. Most of the biochemical and cellular fatty acid properties of strain M9HN-SHQ were typical for bacteria of the Bartonella genus. The strain was susceptible to Cefotaxime sodium, Rifampin, Ciprofloxacin and other four antibiotics. Genotypic characterization of strain M9HN-SHQ, including RAPD, PFGE was distinguishable from the reference strains of B. henselae, B. elizabethae, B. vinsonii subsp. berkhoffii and B. grahamii. Sequence analysis of the genes from the seven chromosomal regions identified the strain M9HN-SHQ as B. clarridgeiae. [Conclusion] To our knowledge, this is the first report that documents Bartonella clarridgeiae infections of domestic cats in China.

Abstract:Abstract: [objective] The primary objective of this study was to identify whether the manganese ions [Mn (II)] transporter genes DR1709 and DR2523 played roles in Deinococcus radiodurans’s radiation resistance. The second objective was to study the relationships among manganese ions, manganese ions transporter genes and the bacterial radioresistance. [Methods] We constructed mutants of DR1709 and DR2523. The wild type and the mutants were treated with UV and hydrogen peroxide (H2O2). The survival fractions of the three strains were analyzed. [Results] Disruption of DR2523 hardly affected the growth of D. radiodurans in tryptone-glucose-yeast extract (TGY) broth. But at each site of the logarithmic stages, the OD600 values of DR1709 mutant (M1709) were much lower than those of the wild type. After being treated with H2O2 and UV, the survival rates of M1709 cells at each dose were much lower than those of the wild type. However, the DR2523 mutant (M2523) and wild type had the similar appearance after being treated with H2O2 and UV, though the wild type had the higher survival than M2523. [Conclusion] DR1709 and DR2523 could protect D. radiodurans from irradiation and superoxide radicals. In D. radiodurans, transporting Mn (II) from the medium was possibly controlled by several different steps. The roles of DR2523 might be partially substituted by DR2283 and/or DR2284, while no other genes could exercise the similar function as DR1709.

Abstract:Abstract: Bacillus subtilis Bs-916 is an effective biocontrol agent in control rice sheath blight caused by Rhizoctonia solani. We identified and analyzed the operon Bac in Bs-916 responsible for synthesis of iturin-like lipopeptides. The research plays an important part in genetic engineered Bs-916 for further improving its bio-control activity. Taking advantage of homologous recombination method, the one mutant obtained by replacement of the Bac original promoter by a constitutive promoter PrepU and designated BGG104; the other mutant was obtained by disruption of the Bac promoter by insertion and designated BGG105. The biological activities results showed the mutant BGG104 enhanced antagonistic activities against several pathogenic fungi and also clearly increased in hemolytic activities. However, the mutant BGG105 decreased clearly in both antagonistic activities and hemolytic activities. Crude lipopeptides were extracted with methanol from precipitates, which were obtained by adding 6 mol/L HCl to the cell-free culture broth. The results of reversed-phase high-performance liquid chromatography (HPLC) analysis of crude lipopeptides showed lipopeptides produced by Bs-916 have a different retention time compared to iturinA. The mutant BGG104 produced up to 3-fold more lipopeptides than Bs-916. However, the mutant BGG105 has not been detected countpart lipopeptides production. The molecular weights of the lipopeptides synthesized by Bac determined by matrix-assisted laser desorption ionization-time of flight mass spectrometry (MS) were 1007.7 Da、1021.7 Da and 1035.7 Da. They were presumed to belong to homologues differed by a structure of –CH2 and their molecular weights were not the same as the other iturin-like liopeptides’, such as iturinA, mycosubtilin and bacillomycin, molecular weights. In conclusion, this paper showed the lipopeptides synthesized by Bac play crucial part in Bs-916 antifungal activities and the lipopeptides overproduction were able to enhance Bs-916 bio-control activities.

Abstract:Abstract: [Objective] SSB2 and SSB3 are ssDNA-binding proteins of Thermoanaerobacter tengcongensis. This work aimed to disclose novel properties of both proteins. [Methods] We performed electrophoretic mobility shift assays (EMSAs) using oligonucleotides spanning the replication origin of T. tengcongensis and non-denaturing polyacrylamide gels. Western blotting assays were used to study the expression patterns of both proteins. [Results] SSB2 bound to 35-nt, 59-nt and 70-nt ssDNA spanning the replication origin and formed one, two or three DNA-protein complexes. The number of the SSB2-DNA complexes was determined by both the length of the ssDNA and the concentration of SSB2. SSB3 formed one more DNA-protein complex with 59-nt or 70-nt ssDNA in comparison with SSB2. Storage of the proteins at -70oC led to the disappearance of one SSB2-(70-nt) complex, or two SSB3-(59-nt) complexes or three SSB3-(70-nt) complexes in the EMSA, indicating the distinct loss of the SSBs’s conformations. Moreover, SSB2 and SSB3 displayed different expression patterns at variable incubation temperatures in vivo. [Conclusion] SSB2 and SSB3 could bind ssDNA with various conformations that were determined by the length of ssDNA, the concentration of the proteins, as well as the temperature of treatment. To our knowledge, this is the first disclosure of the characteristics of SSB2 and SSB3 on 35-70 nt oligonucleotides.

Abstract:Abstract:[Objective] To construct the hp0523 gene mutant of Helicobacter pylori and investigate the function of hp0523 gene. [Methods] We designed and amplified the upstream homologous fragment and downstream homologous fragment of hp0523 gene via PCR method. We constructed the suicide plasmid pBlueKM40-?hp0523 based on allelic exchange. We introduced the suicide plasmid pBlueKM40-?hp0523 into Helicobacter pylori 11637 by electroporation and screened the mutant based on antibiotic selection. We checked the mutant using the PCR and gene sequenced. We performed the coculture of Helicobacter pylori and gastric cell BGC-823 and detected the ability of CagA’s translocation and expression via Western blot. [Results] We constructed the suicide plasmid pBlueKM40-?hp0523 successfully and got the hp0523 deletion mutant. PCR and gene sequenced results showed the gene hp0523 was deleted. The results of CagA translocation assay showed that hp0523 interrupted the translocation of CagA. The comparison between wild-type and mutant showed that hp0523 affected the expression of CagA. [Conclusions] We constructed the hp0523 deletion mutant of Helicobacter pylori NCTC11637. This study suggests that hp0523 gene is an important virulence factor, which may be a component of the apparatus for CagA’s translocation.

Abstract:Abstract: [Objective] To construct recombinant adenovirus carrying C-Terminal of the adhesion factor gene p97 of Mycoplasma hyopneumoniae (Mhp) so as to provide basis for further studying new type Mhp vaccine. [Methods] We amplified p97 gene from the genome of Mhp and cloned into pShuttle-CMV plasmid. The correctly identified recombinant plasmid was linearized with PmeⅠand transformed into E. coli BJ5183-AD-1 competent cells containing adenovirus backbone vector to produce recombinant adenovirus DNA by homologous recombination. Purified recombinant adenovirus plasmid was linearized with PacI, and transfected into AD293 cells to obtain recombinant adenovirus. The recombinant adenovirus was identified by RT-PCR, indirect immunofluorescence assay and Western Blot, and purified by cesium chloride density centrifugation kit, then its titer was determined. Balb/c mice were immunized with recombinant adenovirus via intramuscular and intranasal routes and analysis the immunity results through humoral immunity,mucosal immunity and cell-mediated immunity aspect. [Results] Digestion by PacI proved successful homologous recombination. RT-PCR, Indirect immunofluorescence assay and Western Blot showed that the recombinant adenovirus transcribed and expressed P97 C- terminal protein successfully, the titer could achieve to 5×1011TCID50/mL after purification. Inoculation with the recombinant adenovirus by each route elicited P97 C-terminal protein specific serum and lung homogenate IgG and SIgA was induced by intranasal route, but the special lymphocyte proliferation was not induced by each route. [Conclusion] The recombinant adenovirus expressing p97 C-Terminal gene was successfully constructed and it induced special humoral and mucosal immunity but no cell-mediated immunity.

Abstract:Abstract: [Objective] To study the effects of genes ste7-ste15 double disruption in biosynthesis of Ebosin. [Methods] The ste7 gene was disrupted with a double crossover via homologous recombination in the mutant strain Streptomyces sp. The 139 (ste15 -) and the mutant strain Streptomyces sp.139 (ste7 -ste15 -) were identified by Southern blot. Gene complementation of the knock-out mutant was done. Monosaccharide composition of the exopolysaccharides EPS15-7m, EPS15-7c producing by Streptomyces sp.139 (ste7 -ste15 -) and Streptomyces sp.139 (pKC7-15c) separately were analyzed by Gas Chromatography, while their Mw and the antagonist activity for IL-1R were determined comparing with Ebosin. [Results] The mutant strain Streptomyces sp.139 (ste7 -ste15 -) and complementary strain Streptomyces sp.139 (pKC7-15c) were constructed respectively. The analysis results showed that both of fucose and glucose decreased remarkably in EPS15-7m and its Mw and the antagonist activity for IL-1R were much lower than Ebosin. The composition of fucose and glucose were recovered notablely in EPS15-7c compared with EPS15-7m. [Conclusion] The genes ste7 and ste15 played essential roles in the synthesis process of sugar repeating unit during biosynthesis of Ebosin. The activities of Ebosin new derivative produced by the mutant will be studied further.

Abstract:Abstract: [Objective] To isolate specific bacteria capable of biotransforming isoflavone daidzein. [Methods] Fresh crossoptilon mantchuricum feces was diluted serially from 10-1 to 10-8 in Brain Heart Infusion (BHI)liquid medium in the anaerobic chamber at 37?C. Single colony was isolated and incubated in BHI liquid medium containing 0.1mmol/L daidzein under anaerobic conditions. The culture medium was detected by HPLC method after being incubated for 3 days. [Results] A gram-positive facultative anaerobic bacterium designated strain AUH-HM195 capable of cleaving the C-ring of isoflavone daidzein was isolated. Basic Local Alignment Search Tool (BLAST) search on the GenBank revealed that the full-length of 16S rDNA gene sequence for strain AUH-HM195 has 100% similarity to that of Enterococcus hirae (DSM20160). Based on HPLC retention time, UV spectrum, 1H and 13C NMR analysis, the metabolite of daidzein by strain Enterococcus hirae AUH-HM195 was identified as O-desmethylangolensin. Two peaks were observed when purified O-desmethylangolensin was eluted on a chiral column. The enantiomeric excess (% e.e.) of O-desmethylangolensin was 66.9%. [Conclusion] Bacterial strain Enterococcus hirae AUH-HM195 is the first reported Enterococcus bacterium with C-ring cleavage activity. It is also the first reported facultative bacterium capable of metabolizing isoflavones.

Abstract:Abstract：Objective Dihydroorotate Dehydrogenase (DHODH) catalyzes the rate-limiting step in pyrimidine biosynthesis, and its inhibitors have been developed as drugs for treatment of immune diseases. We studied new DHODH inhibitors from microbial metabolites. Methods We established a rapid and effective high throughput screening method for screening DHODH inhibitors from microbial metabolites. The active compounds were isolated from the candidate strain by column chromatography and preparative HPLC. Results We picked out F01WB-1315 strain as candidate from 4560 fungal strains. We isolated two active compounds F01WB-1315A and B, with IC50 of 0.07 μg/mL and 0.51 μg/mL, respectively. F01WB-1315B could completely inhibit the spleen lymphocytes proliferation stimulated by ConA in vitro, but F01WB-1315A only had 31.62% inhibitory activity. F01WB-1315A, B were identified to be Ascofuranone and Ascochlorin by their physicochemical properties, MS, 13C-NMR and 1H-NMR analysis. Conclusion F01WB-1315A and B are two strong specific DHODH inhibitors and show moderate inhibitory activity against spleen lymphocytes proliferation.

Abstract:Abstract: [Objective] To purify a single fibrinolytic enzyme from Bacillus pseudomycoides B-60 and to determine its N-terminal sequence and to characterize the fibrinolytic enzyme. [Methods] We examined the fibrinolytic enzyme activity by fibrin plate and purified fibrinolytic enzyme by ammonium sulfate fractional precipitation and DEAE anion exchange chromatography. [Results] Obtained a single protein fraction with fibrinolytic activity (BpFE) from B. pseudomycoides B-60. It appeared as a single band in the SDS-PAGE with a relative molecular weight of 34kDa. The fibrinolytic activity of the protein was stable at 4~50℃ and at pH 5~10. The activity sharply decreased above 50℃, and the total loss of activity at pH 3.0. The enzymatic activity was slightly enhanced by the ions of Ca2+, Mg2+, Mn2+ whereas strongly inhibited by Cu2+ ion. Phenylmethyl sulfonyl fluoride (PMSF) could completely inhibit its activity. In addition, the activity improved when the protein was enzymatically hydrolyzed using trypsin and pepsin. The first 15 amino acids of the N-terminal sequence of the enzyme were determined to be VTGTN AVGTG KGVLG. The ?partial amino acids sequence alignment study of the enzyme from B-60 strain with bacillolysin, neutral protease and hydrolase which were from B. cereus, B. thuringiensis, B. anthracis and Lactobacillus sp.was carried out, and there is a 100% homogeneity between them. [Conclusion] We obtained a single fibrinolytic enzyme. Through its N-terminal sequence alignment study, a plasmin with high homogeneity to this protein was not found yet. This provided a basis for further study of new thrombolytic drugs.

Abstract:Abstract: [Objective] We isolated an endophyte PCE45 from the rhizome of Paris polyphylla var. chinensis. From PCE45, we purified and characterized an antimicrobial peptide. [Methods] After ammonium sulfate salting-out, acetone precipitation, SephadexG75,DE52 and SephadexG25 column chromatography, we separated an antimicrobial peptide PCP-1 from the strain PCE45. The stability against high temperature and proteinase, and antimicrobial activity were also analyzed. [Results] The antimicrobial peptide PCP-1 was stable to proteinase and tolerated high temperature, strong acid and strong base. PCP-1 caused deformation of the hyphae of Pyricularia oryzae and prohibited the spore germination. It also inhibited fungi such as Curvularia lunata and bacteria such as Escherichia coli. Mass spectrogram measurement revealed its molecular weight of 1058.3 Da. The amino acid composition of the peptide composed of 7 amino acids. Ninhydrin reaction showed negative trait whereas after acid hydrolysis with positive ninhydrin reaction and biuret reaction. [Conclusion] The ninhydrin reaction and biuret reaction imply that the peptide PCP-1 is a cyclic lipeptide. This is the first report about antimicrobial peptide from Paris polyphylla var.chinensis.

Abstract:Abstract: [Objective] A molecular-based approach for anaerobic fungal community analysis was developed. The diversity of anaerobic fungi in the co-cultures with or without methanogens was analyzed by amplified ribosomal intergenic spacer analysis. [Methods] Co-cultures of anaerobic fungi and methanogens were obtained from rumen digesta using anaerobic fungal medium and the addition of penicillin and streptomycin and ampicillin alternatively and then subcultured 15 times by transferring cultures every 3 d separately for each replicate. At the end of the third subcultures, the co-cultures were inoculated to another bottles adding with chloramphenicol to obtain fungal cultures without methanogens. Total DNA from the original rumen digesta and subcultured co-cultures and fungal cultures was used for amplified ribosomal intergenic spacer analysis. [Results] The diversity of anaerobic fungi decreased corresponding with the subculture of the co-cultuers. The anaerobic fungi represented by 354-375 and 425-438 bp in the amplified ribosomal intergenic spacer analysis profiles were missing in the co-cultures after the second subcultures and the anaerobic fungi represented by 383, 389-391 and 413-418 bp were dominant although the subcultures. The community of anaerobic fungi was different in the co-cultures with or without methanogens. The anaerobic fungi represented by 383.51, 391.44 and 413.55 bp in the amplified ribosomal intergenic spacer analysis profiles were dominant in the co-cultures with methanogens, while the anaerobic fungi represented by 415.80, 425.66, 437.46 and 438.47 bp were dominant in the co-cultures without methangens. [Conclusion] The molecular-based approach amplified ribosomal intergenic spacer analysis was suitable for analysis of anaerobic fungi in the environmental samples. The diversity of anaerobic fungi decreased along with the subculture of the co-cultures and the anaerobic fungal community became stable after the 4th subculture of the co-cultures. The anaerobic fungal community was different in the co-cultures with or without methanogens.

Abstract:Abstract: [Objective] To obtain Newcastle disease virus (NDV) strains with high in vitro anti-tumor effect for construction of recombinant NDV for clinical therapy. [Methods] We used MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphemyltetra-zolium Bromide] assay to examine the anti-tumor effect on A549 and SMMC7721 cells infected by nearly 50 NDV strains. Several assays were used to analyze the apoptosis induced by NDV infection. These assays included:(1) Morphological analysis; (2) Hoechst? fluorescence dye testing; (3) Flow cytometric analysis, and (4) Western blot. [Results] We obtained an NDV FMW strain that inhibited cell growth up to 60% at 48 h postinfection with an MOI (multiplex of infection) of 20. NDV- FMW could elicit apoptosis of infected tumor cells in a dose- and time- dependent manner. We observed the infected A549 and SMMC7721 cells with condensed and fragmented chromatin at 48 h postinfection. Apoptosis peak and hypodiploid cells were revealed by proidum iodide (PI) staining and cell cycle was blocked and arrested in G0/G1 phase in tested cells. Furthermore, annexin-ⅴ/PI staining showed that the apoptotic rates in SMMC7721 cells were 2.1% ,18.5%, 23.8% and 30.4% after treated with 0, 0.2, 2 and 20 MOI NDV-FMW for 48 h respectively. To elucidate the apoptosis pathways induced by NDV-FMW, we detected the expression of active caspase-3 and cleavages of poly(ADP-ribose) polymerase (PARP). We demonstrated that caspase-3 in A549 cells was activated early at 16 h postinfection and PARP was cleaved subsequently. [Conclusion] NDV-FMW had strong in vitro anti-tumor effect on A549 and SMMC7721 cells. Apoptosis of tumor cells induced by NDV-FMW via caspase-3 activation and NDV-FMW could be a potential cancer virotherapy agent.

Abstract:Abstract: [Objective] To construct an attenuated Salmonella choleraesuis vaccine strain expressing the gene SLT-IIeB and FedF of Shiga-like toxin Escherichia coli (SLTEC) O138 with balanced lethal system. [Methods] The gene of SLT-IIeB and FedF of SLTEC O138 was amplified , and then recombined with a vector pYA3493 (Asd+). The recombinant was electroporated into attenuated Salmonella choleraesuis C500(Asd-). The expression of SLT-IIeB and FedF was analyzed by SDS-PAGE. The stability of the vaccine strains was studied by generation culture in vitro. [Results] The stable attenuated Salmonella choleraesuis vaccine strain expressing SLT-IIeB and FedF of SLTEC O138 was constructed with balanced lethal system. The expressed products with protein quality 37000 could react with the antibody of FedF and SLT-IIeB. [Conclusion] The attenuated Salmonella choleraesuis vaccine strain could probably serve as a vaccine against edema disease and piglets paratyphoid.

Abstract:Abstract:【Objective】In order to represent a promising strategy for mucosal vaccination, oral or intranasal immunization of Specific Pathogen Free (SPF) BALB/c mice were performed. The mucosal immunity, systemic immune and protective immune responses were compared after immunization with the recombinant Lactobacillus casei (L.casei) harboring enterotoxigenic Escherichia coli (ETEC) F41.【Method】The recombinant fusion proteins were detected by Western blot. Surface localization of the fusion protein was verified by immunofluorescence microscopy and flow cytometry. Six-week-old female SPF BALB/c mice (160 heads) were divided into 4 groups for immunization and control. Oral and intranasal immunization of mice was performed with the recombinant strain L. casei harboring pLA-F41or pLA. For oral immunization, the mice were inoculated daily on days 0 to 4, 7 to 11, 21 to 25, and 49 to 53. A lighter schedule was used for nasal immunization (days 0 to 2, 7 to 9, 21and 49). Specific anti-F41 IgG antibody in the serum and specific anti-F41 secret immunoglobulin A (sIgA) antibody in the lung, intestines, vagina fluid and feces of mice were detected by indirect ELISA. The mice orally or intranasally immunized with pLA-F41 /L. casei and pLA/L. casei were challenged with standard-type ETEC F41 (C83919) (2×103LD50).【Result】Mice immunized with pLA-F41/L.casei could produce remarkable anti-F41antibody level. More than 90% survived in oral immunization group whereas more than 85% survived in intranasal immunization group after challenged with C83919, all dead in the control group. Ninety percent of the pups survived in oral immunization group whereas 80% survived in intranasal immunization group after challenged with C83919, but only a 5% survival rate for pups that were either immunized with a control pLA vector or unimmunized.【Conclusion】Oral or intranasal immunization with recombinant L. casei displaying ETEC F41 antigens on the surface induced effective and similar systemic and mucosal immune responses against the ETEC F41.

Abstract:Abstract: [Objective] To establish a genetic typing map for Campylobacter jejuni in China by using Pulsed Field Gel Electrophoresis (PFGE). [Methods] A PFGE protocol was developed for subtyping C. jejuni isolates from different sources. The effect of cell suspension concentration, Seakem Gold? agarose gel strength, proteinase K density, washing style, and restriction enzyme concentration were also evaluated. [Results] DNA from 37 isolated strains of C. jejuni digested with restriction enzyme Sma produced PFGE profiles that distinguished these strains to the level of species, and resulted in 6 to 24 bands of electrophoresis. A phyletic evolution tree showed that the isolates could be separated into four genetic lineages, and possessed dominance among lineage Ⅳ. The distribution of isolated strains from different sources overlapped each other in all groups. [Conclusion] PFGE can be used for the investigation of molecular epidemiological patterns of C. jejuni and for tracing the source of C. jejuni in clinical patients. Preliminary data showed that human Campylobacteriosis was related to C. jejuni of animal origin, particularly from the chicken.

Abstract:Abstract: [Objective] To study the structure change of dominant microbial population during activation of stratal microflora under atmospheric pressure (1 MPa) and higher pressure (10 MPa) conditions. [Method] The water sample was from Zhan 3×24 well produced water in Shengli Oilfield. We activated the bacteria in the water sample under atmospheric pressure and higher pressure, and collected samples at different time intervals. These samples were analyzed by denature gradient gel electrophoresis (DGGE). [Results] Based on the analysis of the number and lightness of DGGE bands, we studied the change of the microbial community diversity activation of stratal bacteria. The species number and total quantity of dominant microbial population were not abundant under oil reservoir conditions. After injecting activation agent, some bacteria grew and reproduced quickly along with the enhancement of nutrition condition, and the structure of dominant microbial population changed. [Conclusion] Compared to atmospheric pressure condition, the number of DGGE bands was fewer under higher pressure condition, which indicated that only a few microbial species adapted high pressure conditions. The delayed increase of DGGE bands occurred apparently under higher pressure conditions. In late activation period, the change of DGGE bands was slight, which indicated that, the structure of dominant microbial population readjusted successfully and reached a new dynamic balance.

Abstract:Abstract： [Objective] GX0101 is a recombinant field strain of Marek’s disease virus (MDV) with a long terminal repeat (LTR) insert from reticuloendotheliosis virus, a chicken retrovirus. In this study, GX0101 strain was compared to a very virulent reference strain Md5 for their pathogenicity and transmission ability. [Methods]MDV genomic DNA in feather tips was tested and compared by dot blot hybridization with MDV specific probe in control chickens kept in the same isolators in which chickens were challenged with GX0101 or Md5. [Results] mortality and tumor rates of GX0101 were 28.6% and 7.1% for SPF chickens viccinated against Marek's disease virus.Mortality and tumor rates of vvMd5 were 63.1% and 19.0% in the same viccinated SPF chickens. Mortality and tumor rates of GX0101 were lower than that of vvMd5. However, horizontal transmission ability of GX0101 was stronger than that of Md5. After 28 days challenged by GX0101, MDV was detected in 6 of 15 samples. after 35 days challenged by vvMd5, MDV was detected in 2 of 14 samples. [Conclusion] Horizontal transmission ability of MDV isolates was not necessarily parallel to their pathogenicity.It is suggesting that the increased horizontal transmission may be one of selective competitive advantages. Such advantages may help recombinant viruses with the LTR-insert become more and more popular gradually in chicken flocks.