Di Sun , Cong Liu , Weijie Liu
2019, 59(11):2051-2060. DOI: 10.13343/j.cnki.wsxb.20180529
Abstract:Prodigiosin is a red pigment with multiple biological activities, and of great economic value with promising application. Serratia marcescens is a major producer of prodigiosin, and the model organism for prodigiosin biosynthesis research. This paper reviews recent progresses in transcriptional regulation of prodigiosin synthesis in S. marcescens, illustrating the function of two/multiple component system, quorum sensing system, σ factor and transcriptional regulator in modulating prodigiosin biosynthesis. Moreover, further research focuses are discussed.
Li Chen , Qianzhuo Wei , Kouhei Ohnishi
2019, 59(11):2061-2068. DOI: 10.13343/j.cnki.wsxb.20180548
Abstract:Ralstonia solanacearum causes lethal wilting disease in many economic plants, threatening food security in tropical and subtropical agriculture. It injects type III effectors (T3Es) into the host cells via the type III secretion system. T3Es act as molecular double agents that are involved in either pathogenicity in the susceptible host plants or induction of hypersensitive response in the resistant host plants. A notable feature in this T3E repertoire is the existence of several multigenic families and their various internal repeats. T3Es from multigenic family of R. solanacearum contribute differently to pathogenicity towards the host plants and localize on the plant cell plasma membrane or nucleus. Previous researches demonstrate that the multigenic effectors jointly contribute to the plant disease development but are barely activated individually. However, the pathogenicity mechanism on the most multigenic effectors remains unclear. This review summarizes the recent achievements on elucidating the function of T3Es from multigenic family (GALA, HLK, SKWP, AWR and PopP) in R. solanacearum.
Xiaofei Mei , Zhirong Wang , Jianquan Kan
2019, 59(11):2069-2082. DOI: 10.13343/j.cnki.wsxb.20180559
Abstract:Fruit and vegetables diseases are always caused by pathogenic microorganisms and traditionally, chemical control such as fungicide treatment was widely applied, which helped to cause chemical residues, environmental pollution and resistance in fungi, etc. Alternatively, microbial biocontrol methods were favored due to their safety, effectiveness and environmental harmlessness. In this paper, we reviewed the update investigations about the biocontrol effect and involved mechanisms of Pseudomonas fluorescens, one kind of biocontrol bacteria and plant growth-promoting rhizobacteria. We provided the basic information of P. fluorescens on biological control and discussed related mechanisms including parasitism, competition for nutrients and space sites, production of secondary resistance metabolites and initiation of systemic resistance, responsible for the biocontrol effect. Also, we illustrated the current research result for the improvement of biocontrol efficacy, such as inoculant mixing, physical methods, chemical treatments and molecular technologies.
Ruiqing Liu , Shengyu Li , Yanna Shen
2019, 59(11):2083-2093. DOI: 10.13343/j.cnki.wsxb.20190020
Abstract:Pyroptosis is a form of inflammasome-mediated cell programmed death which exhibits cell lysis upon infection. The activation pathway is divided into canonical pathway via caspase-1 activation and noncanonical pathway via caspase-4/5/11 activation. Recent studies have shown that main effector proteins in pyroptosis are gasdermin (also known as GSDM) family members bearing a novel membrane pore-forming activity. Therefore, pyroptosis is also defined as a cell programmed death mediated by gasdermin. There is cross-regulation between pyroptosis and other immune defense mechanisms so that the host clears infection and relieves damage extent during infection. This review focuses on the function of GSDMD in pyroptosis, research progress of pyroptosis in infectious diseases, and the interaction between pyroptosis and other cell programmed death upon infection. We hope that this review can provide a theoretical basis for the treatment of infectious diseases by targeting pyroptosis.
Jiangrui Zhang , Lihua Zhang , Yibo Shi , Wei Shen , You Fan , Xianzhong Chen
2019, 59(11):2094-2106. DOI: 10.13343/j.cnki.wsxb.20180521
Abstract:[Objective] Sophorolipids are biosurfactants with properties such as solubilization, emulsifying, wetting, foaming, dispersing, and reducing surface tension of conventional surfactants, and tolerance to the environment. Starmerella bombicola can produce sophorolipids, but the components of sophorolipids are complex and difficult to separate. In order to obtain the single high-yield acid type sophorolipid, the strain S. bombicola producing only acid sophorolipid was constructed by metabolic engineering.[Methods] The Rec-six gene editing system was developed using the hygromycin resistance gene as a selection marker. Based on this system, the critical lactonase gene SBLE for lactone-type sophorolipid was knocked out to obtain an engineered strain producing only acid-type sophorolipid. The expression cassette of the UGTB gene (glucosyltransferase) was further integrated into the genome of the recombinant strain and the PXA1 gene (peroxisome membrane transporter) was knocked out to construct a metabolic process yeast strain with high acid-producing sophorolipids.[Results] Compared with the original strain, the yield of oleic acid synthase was increased from 20 g/L to 44 g/L, and the lactone type of sophorolipid was undetectable.[Conclusion] The recombinant S. bombicola can effectively increase the yield of acid-type sophorolipids by over-expressing UGTB and knocking out PXA1 and SBLE, for enhanced the production of acid-type sophorolipid by fermentation.
Zhiguo Liu , Miao Wang , Hongyan Zhao , Dongri Piao , Dianying Lu , Zhenjun Li
2019, 59(11):2107-2116. DOI: 10.13343/j.cnki.wsxb.20180525
Abstract:[Objective] The aim of the present study was to investigate molecular epidemiology and genetic diversity characteristics of Brucella suis strains isolated from 14 different regions in China.[Methods] Biotypes of strains were discriminated by classical identification methods, both geographic distribution and etiology feature of B. suis were analyzed. Meanwhile, MLVA-16 genotyping assay was employed for genotyping of 60 B. suis strains. Diversity of each loci and resolution of genotyping assay were evaluated using online software.[Results] Our data indicated that three B. suis biovars (bv.1, 2, 3) were coexisted and strains numbers was 33, 2 and 24, respectively. Distribution of B. suis was wide and 14 provinces, Guangdong, Guangxi, Inner Mongolia, Beijing, Jilin, Ningxia, Xinjiang and Xizang were included. MLVA-16 approach is an excellent resolution for B. suis population, and diversity index of complete 16 loci was 0.992 based on Hunter-Gaston Discriminatory Index (HGDI). High resolution was observed in panel 1, MLVA-11 and panel 2b, their diversity index was 0.884, 0.916 and 0.979, respectively. Sixty B. suis strains were sorted into 6 clusters and formed 52 genotypes, 5 share (GT24,GT25, GT26, GT28 and GT29) genotypes including 13 isolates. The data indicated that these isolates have potential molecular epidemiology links, which maybe an outbreak from respective common source of infection. Remaining 47 genotypes being represented the single isolates, revealed that there also had unrelated and sporadic cases. A minimum spanning tree for B. suis using MLVA-15 revealed that China B. suis strains had complete identical MLVA-15 Genotypes with strains previously collected in America, France and Argentina.[Conclusion] B. suis strains of this study exhibited higher genetic diversity, as well as high genetic homology with strains obtained from America, France and Poland. The epidemic characterization of B. suis in China was sporadic.
Weiguo Zhou , Dewen Ding , Juan Ling , Xiancheng Lin , Qingsong Yang , Ying Zhang , Manzoor Ahmad , Yanying Zhang , Junde Dong
2019, 59(11):2117-2129. DOI: 10.13343/j.cnki.wsxb.20180535
Abstract:[Objective] This research aims to investigate the response of rhizosphere microbial community after seagrass transplantation to high temperature treated seagrass sediment in Sanya Bay.[Methods] The environmental parameters including pH, dissolved oxygen, phosphate, nitrate, nitrite and ammonium were measured. High-throughput sequencing and real-time quantitative PCR of the 16S rRNA gene were used to analyze the diversity, structure and abundance of microbial communities in the rhizosphere of seagrass Thalassia hemperichii.[Results] The concentration of seawater nutrients (phosphate, nitrate, nitrite, ammonium) and pH were significantly higher in high temperature treatment group after 35 days. The abundance of 16S rRNA gene increased firstly and then reduced with the time. In addition, Firmutes (32.4%), Fusobacteria (27.21%) and Proteobacteria (22.92%) were the dominant phyla in rhizosphere in high temperature treatment group at the beginning of incubation period. But Firmutes and Fusobacteria were then decreased and replaced by Cyanobacteria and Actinobacteria over time. Proteobacteria (51.1%) dominated the rhizosphere microbial communities in the final phase. Moreover, Desulfobacteraceae belonging to sulfate-reducing bacteria and Helicobacteraceae affiliated with sulfate-oxidizing bacteria increased over time.[Conclusion] Colonization of seagrass would improve the microbial diversity of high temperature treated sediment, shape and change the microbial communities in rhizosphere.
Ruolin Wang , Weifang Xu , Fei Wang , Xiaolei Zhou , Yue Zheng , Hongsen Jiang , Jie Xie
2019, 59(11):2130-2143. DOI: 10.13343/j.cnki.wsxb.20180537
Abstract:[Objective] Antagonistic endophytic bacteria were isolated and screened from the healthy stems of mulberry using Boeremia exigua (the pathogen of mulberry snags rotten leaves disease) as target, for the biological control of mulberry snags rotten leaves disease.[Methods] Endophytic bacteria were isolated from mulberry by tissue isolation method, and the antagonistic bacteria with stable antifungal activity were screened out by the combination of inhibition zone method and confrontation culture method. The antagonistic bacterium was identified through morphological features, cultural, physiological and biochemical characteristics and phylogenetic analysis based on 16S rDNA, gyrA and gyrB sequence. The thermal stability and antimicrobial spectrum of cell-free fermentation supernatant were assayed by inhibition zone method and mycelial growth rate method, respectively. Finally, the antimicrobial mechanism was explored through observation the affection of the antagonistic bacteria on B. exigua GXH1, amplification the key genes that were involved in the biosynthesis of antimicrobial active substances, and the lipopeptide compounds produced by antagonistic bacteria were extracted by acid precipitation and analyzed by LC-MS.[Results] In total 17 endophytic bacteria were isolated from healthy mulberry. Among them, strain NPJ13 exhibited strong and stable antagonistic activity against B. exigua GXH1. Morphological features, cultural, physiological and biochemical characteristics analysis results indicated that NPJ13 belongs to genus of Bacillus. Phylogenetic analysis results based on 16S rDNA, gyrA and gyrB genes revealed that NPJ13 strain and several strains of Bacillus velezensis were in the same minimal clade. Therefore, strain NPJ13 was identified as Bacillus velezensis and named B. velezensis NPJ13. The results of thermal stability test showed that strain NPJ13 had superior heat stability. Antimicrobial spectrum showed that strain NPJ13 had different degrees of antagonism against 12 kinds of pathogenic fungi, such as Botrytis cinerea SWU5, Scleromitrula shiraiana SXSG-5, Sclerotinia sclerotiorum PZ-2, Phytophthora nicotianae SWU20 and so on. The hyphaes of B. exigua GXH1 treated by B. velezensis NPJ13 would become distorted, intumescent, broken and more transparent. The results of functional genes detection showed that the genome of B. velezensis NPJ13 contains 5 antimicrobial metabolite synthesis related genes, which are PKSI, NRPS, Sfp, ItuD, Srfc. Surfactins and iturins were detected from the lipopeptide compounds of strain NPJ13 by LC-MS.[Conclusion] The above results indicated that mulberry endophytic bacterium B. velezensis NPJ13 has strong antagonistic activity on B. exigua GXH1, being a candidate strain for developing the biological control agent against mulberry snags rotten leaves disease.
Jie Feng , Hamed I. Hamouda , Naisr Ali , Yuming Wang , Peiyu Zhang , Ming Lv
2019, 59(11):2144-2154. DOI: 10.13343/j.cnki.wsxb.20180549
Abstract:[Objective] Three β-glucan degrading glycoside hydrolases from an extreme thermophilic anaerobic bacterium Caldicellulosiruptor sp. F32 were investigated, including the synergistic effect. The effect of glycosylation on β-glucanase F32EG5 thermostability was also studied.[Methods] Two β-glucanases (F32EG5, Lam16A-GH) and β-glucosidase (BlgA) were heterologously expressed in E. coli. The synergistic effect of all these enzymes on β-glucan degradation was evaluated by 3,5-Dinitrosalicylic acid (DNS) and Thin-layer chromatography (TLC) assays including substrate tolerant abilities. Furthermore, the glycosylated p-F32EG5 was expressed in Pichia pastoris, and compared with F32EG5 from E. coli.[Results] F32EG5 and Lam16A-GH released oligosaccharides with different degrees of polymerization (DP) after hydrolyzing β-glucan. The proportion of low-DP oligosaccharides was increased, when two enzymes used together. BlgA showed excellent synergistic effect with F32EG5 and Lam16A-GH, respectively. Although the glycosylated p-F32EG5 from Pichia pastoris did not obviously change its optimum pH and temperature when compared with E. coli-expressed F32EG5, both thermal stability and catalytic efficiency were found two-folds higher than those of E. coli-expressed F32EG5 at the extreme-high temperature (80-90℃).[Conclusion] F32EG5 and Lam16A-GH showed excellent synergistic effect and substrate tolerant abilities with BlgA. The heterologous glycosylation by Pichia pastoris could improve the thermal stability of F32EG5 under extreme thermophilic environment, which was a benefit during the granulation process of enzyme.
Bing Song , Xuefei Li , Zeyu Shi , Changtian Li , Yongping Fu , Yu Li
2019, 59(11):2155-2164. DOI: 10.13343/j.cnki.wsxb.20180557
Abstract:[Objective] To create new germpla of Pleurotus ostreatus by mutagenic treatments protoplast by 60Co-γ-rays.[Methods] The protoplasts solution was treated by three different radiation doses of 60Co-γ-rays, we analysed the strain lethality rate, and screened the mutant strains by antagonistic reaction and simple sequence repeat (SSR) identification. Finally, we screened a new and fine strain of Pleurotus ostreatus.[Results] The strain lethality rate was 0% under 0.9 KGy, 63.33% under 1.2 KGy, and 76.67% under 1.5 KGy. After the antagonistic reaction and SSR identification, we found 8 mutant strains that were change. The fruiting results showed that the yield and biological efficiency of 7 mutant strains were lower than the control, and the cap color had some change. Compared with the control the yield of 1.5-P4 decreased 41.92%, but the 1.2-P1 was the high-yield strain with yield of 437.95±12.22 g/bag, increased by 9.76% compared with the control.[Conclusion] We screened a new and fine strain of Pleurotus ostreatus by mutation breeding with 60Co-γ-rays, and the results provide reference to mutation breeding of edible and medicinal fungi.
Jie Xiang , Jingshi Chen , Xinxin Xia , Kuai Liu , Shigui Li , Jingang Gu
2019, 59(11):2165-2181. DOI: 10.13343/j.cnki.wsxb.20180565
Abstract:[Objective] To identify the candidate genes and second metabolites involved in NaCl stress response of Trichoderma harzianum ACCC32524, thereby exploring the mechanism of NaCl stress adaptation.[Methods] The transcriptomes of ACCC32524 with the treatment of 0, 0.4, 0.6 mol/L NaCl were compared using Illumina HiSeq XTen high-throughput sequencing and the metabolomes with the treatment of 0, 0.6 mol/L were detected by GC-TOF-MS. The annotation, screening and classification of differentially expressed genes (DEGs) and secondary metabolites were completed by using related softwares and databases. Validation of DEGs using RT-qPCR.[Results] A total of 417 and 733 DEGs were found of ACCC32524 with the treatment of 0.4 or 0.6 mol/L NaCl respectively. GO analysis suggested that total of 318 and 582 DEGs were categorized into three functional classifications (biological process, molecular function, cellular component) and forty sub-categories; COG classification results showed that 232 and 414 transcripts were assigned to the same 20 categories and these transcripts were significantly enriched in various known amino acid transport and metabolism, general function prediction only and carbohydrate transport and metabolism; KEGG pathway analysis revealed that filtered 79 and 96 DEGs were enriched in 25 individual pathways, and those genes were significantly enriched in biosynthesis of amino acids and 2-oxocarboxylic acid metabolism pathways. A total of 22 genes were screened from transcriptome data related with osmotic regulation, ion transport and ROS scavenging. A total of 101 differential secondary metabolites were screened from the metabolome data under 0.6 mol/L NaCl stress, including 8 upregulated and 93 downregulated substances, 36 of which were qualitatively identified and distributed in 9 classifications, such as carbohydrates, organic acids and amino acids. The expression level of selected DEGs was tested with RT-qPCR, and they were consistent with the result of RNA-seq analysis.[Conclusion] Under NaCl stress, a large number of genes and secondary metabolites of Trichoderma harzianum ACCC32524 were changed and the metabolic pathway was significantly shifted. These processes together reduced the toxicity of salt ions to cells and enhanced the tolerance of strains to salt stress. This study further provided the gene information for the research of salt tolerance mechanism of Trichoderma spp..
Wenjin Zhang , Jiaojiao Zhang , Yanhong Li , Yanhong Jiang , Weizhi Yao , Zhengli Wu
2019, 59(11):2182-2193. DOI: 10.13343/j.cnki.wsxb.20190012
Abstract:[Objective] Bacillus cereus is widely used as a probiotic in aquaculture. The aim of this study focusses on the effects of Bacullus cereus S458-1, as previously isolated strain in our lab, on aquaculture water quality and healthy of gibel carp (Carassius auratus gibelio).[Methods] According to the control variable method, we set up the same temperature, salinity, dissolved oxygen and pH in the aquaculture process, used spectrophotometry method to measure chemical indexes, and commercial kit method to determine serum physiological and biochemical indexes of gibel carp.[Results] Compared with the control group (without S458-1), in the Bacillus cereus S458-1 supplemented aquaculture groups, the concentration of soluble reactive phosphorus was significant increased (P<0.05). NH4+ and NO2- converted into NO3-, even the data had no significant difference between the control group and S458-1 supplemented groups. The concentration of serum glutamic-oxaloacetic transaminase, superoxide dismutase, glutathione peroxidase, and malondialdehyde significantly decreased (P<0.05).[Conclusion] Bacillus cereus S458-1 plays important role in aquaculture system, and promotes nitrogen and phosphorus removal, regulates water quality, and enhances healthy condition of the aquaculture animals.
Shoujing Yi , Qingxiao Liu , Zhiyu Jiang , Shuhong Sun
2019, 59(11):2194-2205. DOI: 10.13343/j.cnki.wsxb.20190016
Abstract:[Objective] To study the distribution of extended-spectrum β-lactamase-producing Escherichia coli in Naihe, Taian City, as well as its multiple antibiotic resistance and relative antibiotic resistance genes, and further reveal the mechanism of antibiotic resistance gene transmission.[Methods] We used Kirby-Bauer method to determine the antibiotic resistance profiles, PCR for the detection of antibiotic resistance genes and Class I integrons, and multilocus sequence typing among ESBLs-producing Escherichia coli strains, and conducted the bacterial conjugation test.[Results] We isolated 88 ESBLs-producing Escherichia coli strains out of 272 water samples with the detection rate of 32.4% and the multiple antibiotic resistance rate of 59.1%. Resistance genes including blaTEM, qnrS, AacC2, aac(6')-Ib-cr, oqxA, OXA and AacC4 were detected with the detection rates of 94.3%, 33.0%, 29.5%, 12.5%, 11.4%, 6.8% and 5.6% respectively. 59% of strains carried multiple drug resistance genes. We observed 47 sequence types (STs) in 88 isolates, and 13.6% of them were ST38; we also detected two ST131 strains. The positive rate of Class I integrons was 26.1%, and the predominate gene cassette was dfrA17-aadA5 with detection rate of 13.6%. The conjugation rate was 83.0% (73/88), 72.6% of the conjugates turned into narrower antibiotic resistance profiles. We observed horizontal transfer in all seven antibiotic resistance genes carried by the donor bacteria.[Conclusion] The bacterial multiple antibiotic resistance existed in urban rivers and the resistance genes were capable to transfer horizontally, which could be potential hazard that threatened public health.
Jing Li , Meijuan Xu , Qunfeng Shu , Yawen Zhao , Mi Tang , Xian Zhang , Taowei Yang , Zhenghong Xu , Zhiming Rao
2019, 59(11):2206-2217. DOI: 10.13343/j.cnki.wsxb.20190018
Abstract:[Objective] We modified the bifunctional uridylyltransferase and uridylyl-removing enzyme GlnD to reduce the activity of uridylyl-removing enzyme, thus, increasing the NH4+ transition and application, to improve L-arginine production.[Methods] PII protein GlnK was overexpressed and its uridylation was studied. A glnDAA(including H414A and D415A) mutant was generated from C. glutamicum JNR using the double-crossover chromosome replacement technique. The concentration of NH4+ in the fermentation medium was measured by ion chromatography. Then the resulting strain was cultivated in a 5-L stirring bioreactor to performed a fed-batch fermentation.[Results] The bifunctional uridylyltransferase and uridylyl-removing enzyme was successfully mutated in C. glutamicum JNR and the resulting strain L4 showed a weakened activity of uridylyl-removing enzyme. The shaking flask fermentation showed that the L4 strain consumed more NH4+, and the L-arginine yield was 36.2±1.2 g/L, 22.7% higher than the control strain. The production of L-arginine of L4 strain was 52.2 g/L, which was 25.3% higher than that of L0 strain in 5-L fermentation.[Conclusion] In C. glutamicum, nitrogen is necessary for the L-arginine biosynthesis. We conclude that reducing uridylyl-removing activity resulted in more intracellular GlnK-UMP. The GlnK-UMP interacts with the nitrogen regulator AmtR and enhances the intracellular consumption of NH4+. Subsequently, the increased uptake of NH4+ could promote the L-arginine production in C. glutamicum.
Li Wang , Yun Zhao , Qian Yang , Xin Dai , Yaxin Zhu , Zhiyang Dong
2019, 59(11):2218-2228. DOI: 10.13343/j.cnki.wsxb.20190030
Abstract:[Objective] Screening of novel promoter elements from the genome of microorganisms of extreme environmental origin for the design of synthetic biological chassis cells.[Methods] We used a promoter-probe plasmid pUC18-GFP containing a green fluorescent protein structural gene and a ribosome bind site to construct a rumen metagenomic library. This method allows us to obtain the DNA fragments with constitutive promoter function rapidly and efficiently from this library. We obtained possible promoter regions through the neural network-based promoter prediction analysis. Then, we verified the function of the promoter initiation by using GFP and maltotetraose amylase from Pseudomonas stutzeri as the reporter.[Results] We obtained twenty-two DNA fragments functioning as constitutive promoters from about 3750 transformants. These fragments share very low sequence identities with the reported gene sequences in the NCBI database, and present different starting efficiencies. In addition, we obtained two new promoter fragments RFa1p2 (76 bp) and RFb4p (547 bp) by promoter prediction and sub-cloning. These new constitutive promoters are able to express heterologous proteins efficiently in the absence of any inductor in the genetically engineered E. coli cells.
Jilong Wen , Qi Peng , Xin Zhao , Jie Zhang , Fuping Song
2019, 59(11):2229-2239. DOI: 10.13343/j.cnki.wsxb.20190032
Abstract:[Objective] We analyzed the transcriptional regulation of bkd gene cluster by BkdR and CcpA in Bacillus thuringiensis (Bt), which is involved in leucine, isoleucine and valine metabolism. To determine the mechanism of transcriptional regulation of bkd gene cluster.[Methods] Induced transcriptional activity of bkd promoter (Pptb) was analyzed by promoter fusions with lacZ gene. ccpA insertion mutant was constructed by homologous recombination. Purification of BkdR and CcpA was using HiTrap chelating column. The binding of bkd promoter with CcpA protein was verified by electrophoresis mobility shift assays.[Results] Transcriptional activity of Pptb was induced by leucine, isoleucine, and valine. The induced transcriptional activity of Pptb was sharply decreased in bkdR mutant, but increased in ccpA mutant. Pptb could bind to the BkdR and CcpA protein, respectively.[Conclusion] The induced transcription of bkd gene cluster is positively regulated by BkdR and negatively regulated by CcpA.
Ang Liu , Shuang Wang , Feng Du , Qingjie Xue , Xiuzhen Li
2019, 59(11):2240-2250. DOI: 10.13343/j.cnki.wsxb.20190156
Abstract:Marine bacteria are the major members of marine life. Compared with those living on the land, marine bacteria exhibit high diversity in species, genes and ecological functions, valuable for both fundamental studies and biotechnological applications.[Objective] Isolation and identification of some culturable bacteria from the sea area of Rizhao for screening of agarase producing strains.[Methods] A total of 73 strains were isolated and their 16S rRNA genes were sequenced. Agarsae activity of agar-digesting strains was determined.[Results] These isolates belong to 34 genera, 13 family and 4 phyla, showing rich species diversity. Furthermore, 16S rRNA gene sequence analysis also showed that among these 73 strains, 18 strains potentially represented novel species. Our results also showed that 5 strains were positive for agarase activity and the highest agarase activity of these strains was determined to be 2.17±0.04 U/mL.[Conclusion] This study widens our understanding for the diversity of marine bacteria in species and agarase activity.
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