Abstract:

Abstract:[Objective] Rhizobacterium Pseudomonas chlororaphis GP72 produces two antibiotics, phenazine-1-carboxilic acid (PCA) and 2-hydroxyphenazine (2-OH-PHZ). RpeB is the response regulator (RR) of RpeA/RpeB two-component signal transduction system. We studied the effect of RpeB on PCA and 2-OH-PZH biosynthesis and its genes expression. [Methods] The rpeB gene was amplified from the GP72 genome. The rpeB mutant (GP72BN) was constructed through inserted inactivation of kanamycin resistance cassette and homologous recombination. Phenazines production assay, gene complement experiment and qRT-PCR analysis were used to assess the influence of RpeB on PCA and 2-OH-PHZ biosynthesis and its gene expression. [Results] In KMB media, PCA and 2-OH-PHZ production of rpeB mutant was decreased by 49.5% and 67.3%. The complementation of rpeB could recover the production of these two phenazine antibiotics. The results of qRT-PCR showed that the transcription of phzI/phzR and phzE strongly decreased in rpeB mutant, but the transcription of phzO only decreased a little. [Conclusion] RpeB positively regulates PCA and 2-OH-PHZ biosynthesis, and it might work for upstream of quorum sensing gene phzI/phzR to influence the expression of phz operon.

Abstract:[Objective] This research focus on the influence of rib operon constitutively over-expression and ribC gene low levels expression on the synthesis and accumulation of riboflavin in Bacillus subtilis. [Methods] For the constitutively over-expression of rib operon, its promoter was modified in situ, and the mRNA leader region was replaced by mRNA stabilizer. Using point mutations of its promoter ?35 region, ribC gene transcription level was reduced. The transcription levels of the target genes were analysed by qRT-PCR method. The genetic effects of the modified genes were assessed by measuring the biomass and riboflavin production of the recombinant in shaking flask fermentation. [Results] The relative transcription levels of gsiB stabilizer-modified rib operon have increased about 1 500 times. The first base mutations of ribC promoter ?35 region can lead to its expression levels decreased by more than 97%. With the LB medium supplemented with sucrose 20 g/L, fermentation was completed in 36 h and the resulting recombinant strains LX34 can accumulate riboflavin 2.1 g/L, meanwhile no significant decline in the biomass. [Conclusion] The gsiB mRNA stabilizer can effectively improve transcription levels of the target gene or operon. A point mutation in the first base of promoter ?35 region can effectively reduce the transcription of ribC gene. The over-expression of rib operon and the expression reduced significantly of ribC gene result in the accumulation of riboflavin.

Abstract:[Objective] Identified six thraustochytrid strains isolated from Shenzhen costal seawater and sediment. Morphological characteristics, life cycle and fatty acid profiles of these strains were studied. [Methods] Thraustochytrid strains were isolated using pine pollen as bait and identified based on 18S rRNA gene sequences. Morphological characteristics were observed using microscope. Nile red staining was used to qualitatively analyze oil content. While GC-MS were used to analyze specific fatty acid profile. [Results] Analysis in 18S rRNA gene revealed that they belong to three genera Aurantiochytrium sp., Schizochytrium sp. and Thraustochytrium sp.. Among these strains, Mn11 and Mn15 were found to produce high level of saturated fatty acid, which is more than 70% total fatty acid. While Mn16 and Sw7 showed high capacity of DHA production with 1.29 g/L and 1.26 g/L DHA yield. [Conclusion] Mn11 and Mn15 strains were suitable for biodiesel production while Mn16 and Sw7 were promising DHA producing strains.

Abstract:Antarctic ice algae Chlorophyceae L-4 is an important component and primary productivity of Antarctic ecosystem. It has specific physiological mechanism for longtime survival in the polar environment. When living environment and conditions get change, membrane-lipid system and protein level varies. Ultrastructure of ice algae also changes under heavy metal stress. [Objective] To observe Chlorophyceae L-4 state under Hg2+ stress, and study Hg2+ enrichment and influence on antioxidant system of Chlorophyceae L-4. Then provide theoretical foundation for Antarctic environmental monitoring. [Methods] Drew growth curve of Antarctic algae in different concentration stress conditions of Hg2+and algae ultrastructure observation. Measured MDA content and SOD enzyme activity. Detected Hg2+ enrichment rule by ICP-MS. [Results] Cell count decreased in lower Hg2+ concentration (≤100 μg/L), and in higher concentration (≥250 μg/L), algae cells died. MDA content increases as Hg2+ concentration increased. SOD enzyme activity was enhanced at first and then decreased. Hg2+ enrichment reaches a peak value within one hour and after that, enrichment value reduced slightly. [Conclusion] Hg2+ would be inhibiting and poisonous to the growth of algae. Hg2+ has obvious adverse influence on Chlorophyceae L-4 antioxidant system. Hg2+ absorption of L-4 reach saturation in one hour. Enrichment amount of Hg2+ decreased slightly when it is over concentrated.

Abstract:[Objective] Conversion of phosphorus to phosphine, a gaseous form of phosphorus, has the potential to remove phosphorus from wastewater. [Methods] Incubator was kept anaerobically for 160 days, with paddy soil as inoculum that was treated either with phosphine without phosphine, under the condition ORP≤?300 mV, 35 °C and in dark. [Results] In incubator 1, total phosphorus removal in the effluent reached 25%, with the highest rate of 26.8%, and the gas phosphine output was above130 ng/L; and in incubator 2, total phosphorus removal in the effluent reached 23% with gas phosphine output of 126 ng/L. [Conclusion] Microorganisms from paddy soil can form a stable system to produce phosphine from phosphorus under anaerobic conditions to remove phosphorus contamination in soils.

Abstract:[Objective] To investigate the impact of large-scale planting water hyacinth (Eichhornia crassipes) on the cultivable bacterial community structure and diversity in the eutrophic lake. [Methods] Diluting plate counting method was applied to monitor the cultivate bacteria communities in three water hyacinth planting areas composed of purple root water hyacinth planting area (ZW), wild-type water hyacinth planting area (PW) and non-planting sites (control, CK), and then the 16S rRNA gene of the isolates were sequenced. [Results] 54, 49 and 40 isolates with various morphological characteristics were obtained from ZW, PW and CK, respectively. The Shannon-Wiener diversity indexes were 3.17, 3.07 and 2.73, respectively. And the quantities of the culturable bacterial in ZW, PW and CK were 1.35′107 CFU, 8.35′106 CFU, 2.70′106 CFU of per Liter, respectively. The 16S rRNA sequencing result showed that at the common and dominant phylum species among the three sampling sites were Alphaproteobacteria, which accounting for 35.1%, 32.4% and 40.0% of total culturable bacteria, and Actinobacteria which accounting for 18.9%, 32.4% and 20.0%, and Betaproteobacteria which accounting for 13.5%, 5.9% and 16%, and Gammaproteobacteria which accounting for 13.5%, 14.6% and 12.0%, and Bacteroidetes which accounting for, 13.5%, 8.8% and 8.0%, and Firmicutes which accounting for 2.7%, 5.9% and 4.0%, respectively. Only ten genera Sphingopyxis, Rhodobacter, Xanthobacter, Novosphingobium, Sphingomonas, Pseudomonas, Microbacterium, Steptomyces, Flavobacterium and Bacillus were shared by all the three water samples. [Conclusion] This study indicates that large-scale planting water hyacinth could both increase the cultivated bacterial diversity and modify the bacterial community composition in the eutrophic lake.

Abstract:[Objective] Unveil the characteristics of prokaryotic (bacteria and archaea) community structure of household biogas digesters in the tropical climate zones of Yunnan. [Methods] 16S rRNA gene clone library technique was constructed to study prokaryotic (bacteria and archaea) diversity of the household biogas digesters in Yunnan (north) typical tropical climate zones. [Results] Total 330 effective sequences of bacteria were obtained and divided into 108 OTUs, bacterial library coverage is 81.5%; 185 archaeal effective sequences were obtained and divided into 17 OTUs, archaeal library coverage is 97.8%. A typical sequence in each OTUs was selected and to perform similarity comparison and analysis in the GenBank database, the results showed that: most bacteria are uncultured bacteria (24.19%), the dominant bacterial phyla include Bacteroidetes (23.58%), Chloroflexi (21.46%), Firmicutes (13.91%) and Proteobacteria (8.74%); the dominant archaeal group is Methanosaeta (76.75%) of the order Methanosarcinales which is aceticlastic. In addition, a small amount of uncultured Crenarchaeota archaea (9.19%) was detected. [Conclusion] The results showed that microbial species are very rich in the household biogas digesters of Yunnan (north) typical tropical climate zones, different microbial species have obvious differences in the abundance and have obvious dominant population, and the diversity of bacteria is more abundant than that of archaea.

Abstract:[Objective] Investigate the effect of pH, initial Cr(VI) concentration, the existence of Fe(III) and oxygen concentration on Cr(VI) reduction conducted by A. cryptum XTS, and monitor differential expression of the functional gene involved in Cr(VI) reduction process. [Methods] The orthogonal experiment L9(34) has been utilized to find the optimal condition for Cr(VI) reduction; The sequence of gene Acry_2099, which is thought to be involved in Cr(VI) reduction pathway of A. cryptum XTS has been cloned and analyzed. [Results] It has been shown that the optimal condition of Cr(VI) reduction by A. cryptum XTS is at pH 2.9 under the help of 100 mg/L ferric ion with initial 80 mg/L Cr(VI). In this condition, 67.48% Cr(VI) has been reduced in 24 hours. In addition, Acry_2099 has been cloned and its sequence shares 99.7% similarity with its homolog in A. cryptum JF-5, the model A. cryptum species. The alternation of Acry_2099 expression level correlates with the ability of Cr(VI) reduction in different condition including different pH, initial Cr(VI) concentration as well as oxygen concentration, which suggests Acry_2099 may be involved in Cr(VI) reduction pathway. Even though the addition of ferric iron can enhance the Cr(VI) reduction by A. cryptum XTS, ferric iron addition have no obvious influence on Acry_2099 gene expression. [Conclusion] The environmental factors including pH, initial Cr(VI) concentration, the existence of Fe(III) and oxygen concentration greatly affect the ability of reducing Cr(VI) by A. cryptum XTS. To be specific, low pH and high initial Cr(VI) concentration promotes A. cryptum XTS ability to reduce Cr(VI).

Abstract:[Objective] In order to enhance production of L-phenylalanine (L-Phe) by recombinant Corynebacterium glutamicum, the composition of culture medium was optimized. [Methods] Using orthogonal experiment and response surface methodology, the optimal medium of seed and fermentation was obtained for the production of L-Phe by recombinant C. glutamicum. [Results] The optimal seed medium (g/L) was comprised of glucose 25.0, corn steep liquor 25.0, (NH4)2SO4 15.0, MgSO4 1.0, KH2PO4 2.0, Urea 2.0 and pH was 6.8?7.0. The optimal fermentation medium (g/L) contained glucose 110.0, corn steep liquor 7.0, (NH4)2SO4 25.0, MgSO4 1.0, KH2PO4 1.0, sodium citrate 2.0, glutamic acid 1.0, CaCO3 25.0 and pH 6.8?7.0. Accordingly, L-Phe production (9.14 g/L) was increased by 22.5%. [Conclusion] The production of L-Phe was significantly increased after optimization and three key factors (glucose, corn steep liquor and (NH4)2SO4) were identified for the production of L-Phe through the orthogonal experiment and response surface analysis, which might provide a foundation for the scale-up culture in the future.

Abstract:[Objective] To study secondary metabolites of special eco-environmental microorganism— Xenorhabdus bovienii PacYellow, and to provide structurally diverse compounds for microbial drug/pesticide development. [Methods] The strain PacYellow was identified by comparison of 16S rRna gene. The secondary metabolites were purified by thin-layer chromatography, silica gel column chromatography, gel chromatography, and semi-preparative high-performance liquid chromatography. The structures were elucidated by using spectroscopic technologies including nuclear magnetic resonance (NMR), infrared spectroscopy (IR) and mass spectroscopy (MS). [Results] The strain PacYellow was identified as a strain of Xenorhabdus bovienii. Four compounds were purified and their chemical structures were elucidated as indole derivatives that are probably biosynthesized from tryptophan and valine or isoleucine. [Conclusion] Four indole derivatives were identified from entomopathogenic bacterium Xenorhabdus bovienii PacYellow.

Abstract:[Objective] To study the transcriptional regulation of nirS encoding nitrite reductase and the function of nirS involved in the denitrification process of Pseudomonas stutzeri A1501. [Methods] The nirS-lacZ fusion vector was constructed and transformed to A1501 and rpoN mutant strains by triparental conjugation. The β-galactosidase activity was detected to analyze the expression of the nirS gene in A1501 under different concentrations of oxygen, nitrate and nitrite. The fusion vector was also transformed to the rpoN mutant to investigate the effect of RpoN on the transcription of the nirS gene through β-galactosidase activity analysis. Furthermore, we constructed the nirS mutant strain by homologous recombination and investigated the function of nirS as it is involved in the denitrification process. [Results] Expressional activity of the A1501 nirS promoter under anaerobic conditions was four-fold higher than that under aerobic conditions. Nitrate significantly induced the expression of nirS, while nitrite showed only slight induction of the nirS promoter. Compared to the wild type, one fourth of the nirS expression was observed in the rpoN mutant. No conserved RpoN binding sites were found in the nirS promoter region, suggesting that RpoN regulates nirS expression through an indirect pattern. The denitrification capability of ΔnirS was reduced by about 20% compared to the wild type when nitrate was used as the sole electron receptor, while the ΔnirS had little denitrification with nitrite as the sole electron receptor, thus the utilization of nitrite was apparently decreased in ΔnirS. Compared to the wild type, the nitrogenase activity of ΔnirS was increased under anaerobic conditions with nitrite. [Conclusion] The transcription of nirS in A1501 was influenced not only by anaerobic conditions and nitrate, but also under the control of RpoN. The nirS played a key role in the denitrification process of A1501, which is involved in nitrite metabolism.

Abstract:[Objective] The result of this study will provide evidences for the exploration and utilization of plant endophyte from Stipa capillata on alpine meadow, and provide a valuable resource for the study of biological fertilizer. [Methods] This test exploited the conventional methods of separation of endophytic bacteria 265ZY4 from Stipa capillata, and the strain was studied by 16S rRNA sequence analysis and biological characteristics including antibacterial activities, IAA secretion, phosphate solubilization and nitrogen fixation by using in vitro antagonistic tests, Salkowski colorimetry and Mo-Sb colorimetry. [Results] Strain 265ZY4 demonstrated inhibitory activities to three fungal pathogens of potato, the best inhibitory rate of the strain were 83.03% against Colletotrichum coccodes. IAA was secreted by 265ZY4 as high as 9.30 mg/L in the King medium without addition of tryptophan, The strain also possessed the capacity of phosphate solubilization and without the capacity of nitrogen fixation. With the cultural and morphological characteristics, combined with 16S rRNA sequence analysis, the strain 265ZY4 was identified as Bacillus subtilis. [Conclusion] Strain 265ZY4 was preliminarily identified as B. subtilis, and has the good biological function. It should be an interesting isolate for developing agriculture.

Abstract:[Objective] To analyze the genotype of Methicillin-resistant Staphylococcus aureus (MRSA), discover the epidemiology and evolutionary pattern of MRSA and provide a scientific basis for prevention and control of MRSA in Hangzhou area. [Methods] In total 86 MRSA strains were characterized by spa typing, multi-locus sequence typing (MLST), staphylococcal cassette chromosome mec (SCCmec) typing. Results were compared with prevalent genotypes of MRSA reported worldwide to analyze the evolutionary relationships. [Results] The 86 MRSA isolates were classified into 13 spa types and 9 STs, which were further categorized into 4 groups and 8 clonal complex. The SCCmecⅡwas the predominant genotype (61.6%), followed by SCCmec-III (22%), 5 strains of CA-MRSA (SCCmecⅣ). SCCmec-II-ST5-t311-CC5 and SCCmec-III-ST239-t030/t037-CC239 were the main clones, representing for 47.7% and 12.8%, respectively. [Conclusion] SCCmec-Ⅱ-ST5-t311 was the most prevalent strain of MRSA in Hangzhou area. The emergence of CA-MRSA strains suggested that MRSA has spread from hospitals to community in Hangzhou. In addition, the strains (SCCmec-Ⅰ-ST1921-t164-CC20 and SCCmec-Ⅳ-ST965- t062-CC5) developed a new variant strain that needs more attention.

Abstract:[Objective] Inhibition of lactobacilli metabolites on Streptococcus pyogenes was analyzed. [Methods] Three lactobacilli strains was grown in MRS broth overnight, then the culture supernatants were collected and evaluated for inhibitory activity. Inhibition was determined by measuring inhibition zone diameters with double plate punching method. Then HPLC and 4-Aminoantipyrine were used to determine the concentration of organic acids and H2O2 respectively in lactobacilli metabolites. Finally, minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of lactic acid, acetic acid and H2O2 on S. pyogenes were determined. [Results] Lactobacillus plantarum KLDS1.0667 had the strongest inhibitory effect among the three strains, followed by L. paracasei KLDS1.0342-1 and L. helveticus KLDS1.0203. L. plantarum KLDS1.0667 had the highest production of lactic acid and acetic acid, followed by KLDS1.0342-1 and KLDS1.0203. However, L. helveticus KLDS1.0203 had the highest production of H2O2, followed by KLDS1.0667 and KLDS1.0342-1. The diameters of inhibition zone all decreased after elimination of H2O2 in lactobacilli supernatants, and no obvious inhibition zones were detected when the pH of lactobacilli supernatants was adjusted to 7.0. The results indicated that organic acids and H2O2 were the main inhibiting substances in lactobacilli metabolites, further lactic acid was the most important inhibiting substance. MIC of lactic acid, acetic acid and H2O2 on Streptococcus pyogenes were 1.28, 0.64 and 0.008 g/L, respectively. MBC of lactic acid, acetic acid and H2O2 on Streptococcus pyogenes were 5.12, 2.56 and 0.032 g/L, respectively. [Conclusion] The metabolites of lactobacilli could inhibit the growth of Streptococcus pyogenes, and the organic acids and H2O2 were the main inhibiting substances.

Abstract:[Objective] This experiment was made to obtain a preliminary understanding of pollution of Pseudomonas aeruginosa in the production process of mineral water and spring water. Pathogenicity and antibiotic resistance of P. aeruginosa of mineral water and spring water were analyzed. [Methods] This experiment based on 108 samples from 36 mineral water and spring water factories in 9 provinces. According to the methods for examination of drinking natural mineral water (GB/T8538-2008), the pollution rates and pollution levels of P. aeruginosa had been obtained. The tests of virulence gene and antibiotic resistance were tested on collected P. aeruginosa isolates. [Results] The pollution rates of source water, activated carbon filtered water and finished products of mineral water were 16.7%, 16.7%, 0 respectively. The pollution levels of source water, activated carbon filtered water and finished products of mineral water were 3.7, 2.0, 0 CFU/250 mL respectively. The pollution rates of source water, activated carbon filtered water and finished products of spring water were 66.7%, 83.3% and 5.6% respectively. The pollution levels of source water, activated carbon filtered water and finished products of spring water were 5.1, 7.3, 2.0 CFU/250 mL respectively. The virulence gene and antibiotic resistance tests of 36 P. aeruginosa isolates showed that the detection rates of exoU, exoS, phzM, toxA and lasB were 25.0%, 75.0%, 100%, 88.8%, 100% respectively; 36 P. aeruginosa strains were sensitive to 14 kinds of antibiotics which were selected according National Committee for Clinical Laboratory Standards of The United States of America. [Conclusion] The pollution rates of source water, activated carbon filtered water and finished products of spring water were significantly higher than mineral water. Both the pollution levels of 2 kinds of water samples were relatively low and there was no greater than 40.0 CFU/250 mL of the sample. The activated carbon filtered water of spring water was the highest pollution rate among all samples, which indicated that most of the factories had some microbial pollution in the activated carbon filter link. The high detection rates of virulence genes, including exoU, exoS, phzM, toxA and lasB in 36 strains of collected P. aeruginosa were analysed. All 36 isolates of collected P. aeruginosa were sensitive to 14 kinds of antibiotics.

Abstract:[Objective] The influence of wild blueberry and anthocyanins extract on gut microbiota of high-fat diet-induced C57BL/6 mice was investigated. [Methods] The C57BL/6 mice were fed with high-fat diet and supplemented with blueberry or anthocyanins extract. Twenty-five germ-free mice were divided into five groups: normal chow diet (NCD), NCD+10 g/100 g blueberry (NCD+BB), high-fat diet (HFD), HFD+10 g/100 g blueberry (HFD+BB), HFD+20 mg/100 g anthocyanin (HFD+ACN). During the ten weeks, food intake, caloric intake and body weight were measured weekly, and dynamic changes of intestinal flora were monitored by DGGE. [Results] There was no significant difference in food intake among these five groups. Average caloric intake was higher in mice fed HFD+BB and HFD+ACN diets compared to the NCD+BB diets. Although body weight gain of mice fed with HFD+BB increased most obviously, no significant difference in body weight was observed between the groups at ten weeks. As the research went on, the diversity of intestinal microorganisms in HFD group, HFD+BB group and HFD+ACN group changed dramatically. The similarity coefficients of PCR-DGGE profile in intestinal flora between HFD+BB group and NCD group was lowest. However, as for HFD+ACN group and NCD group, the value is higher compared with HFD group and NCD group. The sequencing results of the dominant bands revealed that dietary supplemented with blueberry or anthocyanins extract can significantly reduce the number of obesity-associated Firmicutes. [Conclusion] Wild blueberry and anthocyanins extract can modify the structure of the intestinal microbiota, simultaneously protect against imbalanced intestinal microorganisms of the high-fat diet-induced mice, and ameliorate obesity and attenuate lipid accumulation potentially.

Abstract:[Objective] Mutants of Isochrysis zhangjiangensis were screened for fast growth and high oil productivity. [Methods] Atmospheric and room temperature plasma jet mutation technique was used to mutate I. zhangjiangensis, and mutants were screened by different cultivation volume such as 96-well plates, flasks and bioreactors culture. [Results] After thirteen times passaged, mutant IM110020 was cultivated for 7 days in 600 mL bioreactor for evaluation. The maximum specific growth rate, cell density and lipid productivity could reach up to 0.72 d?1, 16 750×104 cells/mL and 109.8 mg/(L·d), respectively, which were 12.5%, 20.8% and 17.9% better than those of the wild strain correspondingly. [Conclusion] We obtained a mutant IM110020 with fast growth and high oil productivity, and the properties were stable after thirteen passages.

Abstract:[objective] Calcimycin, a divalent cation specific ionophore, is a pyrrole moiety containing polyther antibiotic, widely used to study the biological function of divalent cation in eukaryotic cells. The biosynthetic mechanism of calcimycin remains to be fully elucidated. calD is a gene with unknown function in the calcimycin biosynthetic gene cluster. The aim of this study is to identify the function of calD in calcimycin biosynthesis pathway. [Methods] Bioinformatic analysis was used to predict the function of calD. PCR targeting was used to disrupt calD in Streptomyces chartreusis NRRL 3882. HPLC/MS was used to analyze the fermentation product. [Results] Bioinformatic analysis shows that CalD belongs to the family of alcohol dehydrogenase. The calD gene disruption mutant was obtained. The mutant was also complemented with calD. HPLC analysis shows that inactivating of calD decreases but not abolishes calcimycin production. The yield of N-demethylcalcimycin is also decreased. The calD mutant accumulates hydroxyl-cezomycin. [Conclusion] calD participates in calcimycin biosynthesis. It might be responsible for the oxidative conversion of the hydroxy-cezomycin to keto-cezomycin. This result paved way for the further analysis of the biochemical function of calD.

Abstract:[Objective] Endophytic fungi of medicine plants are the new microbial resource of antibiotic medicines. These antibacterial mechanisms of endophytic fungi named JY25 from Gynostemma pentaphyllum have important significance for the research and development of endophytic fungi. [Methods] The method of double dilution has adopted to measure the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of fermentation broth to Escherichia coli. Then, the JY25 fermentation broth with MIC concentrations was used to inhibit the growth of E. coli, and the morphology changes of E. coli were observed by scanning electron microscope. Meanwhile, β-galactosidase, alkaline phosphatase and conductivity were used to test the damaged effects of fermentation broth on E. coli cell membrane and cell wall. Finally, the effects of protein synthesis of E. coli were detected by coomassie blue method. [Results] The results showed that MIC of JY25 fermentation broth to E. coli was 7 g/L, MBC was 14 g/L, and the fermentation broth with MIC concentration could delay the logarithmic growth of E. coli up to 12 h, with severe deformity and damage of cell morphology. With the extension of treating time, both the β-galactosidase activity and conductivity increased, and the protein synthesis was abnormal. The alkaline phosphatase did not be detected in the broth. [Conclusion] JY25 endophytic fungi from Gynostemma pentaphyllum primarily inhibited the growth of E. coli by damaging the cell membranes and impacting protein synthesis.

Abstract:[Objective] With the use of anti-retroviral therapy (ART) for HIV-infected individuals, a greater control of viral replication is now possible. In 2012, however, more than 35 million people were living with HIV-1 and more than 1.6 million people died of AIDS or HIV-1 related diseases worldwide. One of the main reasons for difficulties in completely eradicating HIV-1 in vivo is the reservoir problem. Although the CD4+ T-cells and monocytes or macrophages are thought to be the reservoir of HIV-1 in vivo, the viral replication mechanism in monocytes or macrophages is yet to be studied, as compared with that of CD4+ T-cells, because of the lack of an appropriate system. Thus, to evaluate the effects of the activating or differentiating signals in monocytes on the replication of HIV-1, we attempted to establish the HIV-1 latently infected human monocyte cell lines. [Methods] We used two recombinant HIV-1 viruses, NLnGFP-Kp and NLnNanoLuc-Kp, which have a frame-shift mutation in the env region and have EGFP or NanoLuc gene, respectively, as a marker in the nef region. Two human monocyte linage cell lines, THP-1 and U937 cells, were each infected with one of the two viruses. For cloning of the infected cells, the limiting dilution method was used and the expression levels of these marker genes were determined by flow cytometry or luciferase assay. From the cell clones not expressing either marker gene, we selected latently infected cell clones after stimulating them with phorbol-12-myristate-13-acetate (PMA). [Results] We obtained four cell clones that were considered to be latently infected with HIV-1. Two of them from THP-1 had EGFP as a marker and two of them from U937 had NanoLuc as a marker. All these cell clones expressed their marker genes when stimulated with PMA but in the steady state condition of their cultures at an undetectable level. [Conclusion] We established four cell clones latently infected HIV-1 from human monocyte lineage cell lines. These cells can be a useful tool for a better understanding of the transcriptional regulation mechanisms in the HIV-1 replication.

Abstract:[Objective] To define and compare the parameters for the heat and formaldehyde inactivation of Brucella strains, and provide information for preparation of Brucella inactivated antigen. [Methods] The four Brucella virulent reference strains 2308 (B. abortus), M28 (B. melitensis), S1330 (B. suis) and 16M (B. melitensis) were cultivated in TSA media, and the harvested culture were resuspended to a concentration of (4?8)×1010 CFU/mL by saline. Then the suspension was divided into the equal two parts for heat inactivation at 80 oC for different time or formaldehyde inactivation at different concentration and for different time at 37 oC, and the inactivation effects for the two methods were compared. The rabbits of 1.5?2.0 kg were subcutaneously inoculated with the heat or formaldehyde inactivated 16M antigen at the dosage of 1×1010 CFU/mL. The serum antibody titer was measured weekly during six weeks post inoculation by Rose Bengal test (RBT) and Serum agglutination test (SAT). [Results] It takes 5 min to inactivate Brucella strains 2308, S1330 and 16M by heating at 80 oC, and 10 min for all four strains. The four Brucella strains could not be completely inactivated while incubated in 0.2% formaldehyde even for 7 days. The strains 16M and M28 could be inactivated thoroughly via incubation in 0.4% formaldehyde for 12 or 72 hours, respectively. Although the effect varied for the inactivation of strains 2308 and S1330 in two independent experiments, the four strains could be entirely inactivated by incubation in 0.6% formaldehyde for 72 hours. The fluctuation trends were almost consistent for the stimulated serum antibodies against the two heat or formaldehyde inactivated 16M antigens. Moreover, the antibody titer against the formaldehyde inactivated antigen was slightly better than that against the heat inactivated antigen. [Conclusion] Heat inactivation at 80 oC and inactivation in 0.6% formaldehyde could be used to prepare Brucella inactivated antigen and did not change the immunogenicity of Brucella.

Abstract:Treating infections caused by multi-drug resistant pathogenic bacteria is a challenge worldwide. It is critical to develop novel antimicrobial agents. Lysins are highly efficient peptidoglycan hydrolases which are encoded by bacteriophages. Because of their special advantages of co-evolution with bacteria and natural selectivity, lysins could kill multi-drug resistant bacteria with high efficacy and very low possibility of developing resistance. In the present review, the structures and functions of lysins are outlined, and the recent research progress in lysin therapy of bacterial infections is summarized.

Abstract:Bifidobacterium is an important category of probiotics. It is widely used in the dairy production and microecological preparation. This paper summarized the evolution and classification of Bifidobacteria in “Bergey’s Manual of Systematic Bacteriology”. Moreover, the polyphasic taxonomy research of Bifidobacteria was involved, and we detailedly discussed the new species of Bifidobacterium so far.

Abstract:Infective endocarditis (IE) remains one of the major diseases, which poses a serious threat to human health. In recent years, human being is facing an increased incidence rate of IE and therefore accurate diagnosis and effective treatment as well as preventive measurements become urgent clinical and public health issues. This review?summaries the recent progress of IE in laboratory diagnosis, treatment, the risk factors and preventive measures concerning Bartonella species and BE, including 538 Bartonella endocarditis (BE) cases and their epidemiology. It is anticipated that associated studies have substantial significance on the understanding and control of BE of human being.

Abstract:The cell surface hydrophobicity of environmental microorganism has important influence on its metabolism during cell growth process, and had wide applications in the field of environmental biotechnology. Currently, microbial adhesion to hydrocarbon (MATH) was popularly employed for characterizing the cell surface hydrophobicity. This method was widely used in environmental remediation, bioengineering, medical and food processing field owing to its advantages of simplicity, convenience and accuracy. This paper reviewed recent studies of MATH applied in sludge characteristic, degradation of refractory organics, membrane fouling and biological demulsification. The modified studies on MATH were also introduced in operating factors, counting methods and data analysis. Finally, the future research prospect in this field was also proposed.

Abstract:Antibiotic resistance is present in different species of lactic acid bacteria strains, which poses a threat to food safety. In this paper, the mechanisms of antibiotic resistance, sensitive detection methods, as well as antibiotic resistance situation and transferability of lactic acid bacteria in fermented foods were reviewed which can provide references for peer researchers.

Abstract:In order to improve the teaching effect of Food Microbiology and promote students to develop scientific epistemology and methodology, the materialist dialectic views, such as diversity and unity, commonality and individuality, absoluteness and relativity, external and internal factors, were applied throughout teaching practice. In addition, more scientific teaching content and process can be designed according to the perspective of dialectics. The application of materialist dialectics not only changed the students’ way of thinking, but also enhanced the intrinsic and logical link of course contents, and hence it obviously improved the teaching effectiveness.

Abstract:To improve the classroom teaching quality, we applied diverse teaching methods, such as heuristic method, cased-based method, and problem-based learning method, according to the characteristic of medical microbiology. These methods help the students master the knowledge, arouse the students’ interests and innovation spirit. Furthermore, they enhance the ability of the students to discover, analyze and solve problems.