Production of Avaroferrin and Putrebactin by Heterologous Expression of a Deep-Sea Metagenomic DNA

The siderophore avaroferrin (1), an inhibitor of Vibrio swarming that was recently identified in Shewanella algae B516, was produced by heterologous expression of the biosynthetic gene cluster cloned from a deep-sea sediment metagenomic DNA, together with two analogues, bisucaberin (2) and putrebactin (3). Avaroferrin (1) is a macrocyclic heterodimer of N-hydroxy-N-succinyl cadaverine (4) and N-hydroxy-N-succinyl-putrescine (5), whereas analogues 2 and 3 are homodimers of 4 and 5, respectively. Heterologous expression of two other related genes from culturable marine bacteria resulted in production of compounds 1–3, but in quite different proportions compared with production through expression of the metagenomic DNA.     

微生物与根际中物质的循环(综述)

由于大量能量物质的投入,使根际成为土壤微生物非常活跃的一个区域和土壤-植物系统中物质和能量的交换十分频繁的一个界面。微生物积极参与了这个微生态系统中的能量和物质的循环过程,并成为其中非常活跃的一个组分。它们的代谢活动不但影响植物的生长和发育,而且也是影响土壤和大气之间气态物质交换的一个不可忽视的因素。     

吡咯伯克霍尔德氏菌JK-SH007产嗜铁素的相关基因克隆及条件优化

为了明确吡咯伯克霍尔德氏菌Burkholderia Pyrrocinia JK-SH007是否产嗜铁素，揭示其生防机制，本文通过CAS检测该菌株产嗜铁素的能力，并对其嗜铁素合成相关基因cepR进行克隆及序列分析，同时采用单因素试验及响应面法对菌株JK-SH007产嗜铁素条件进行优化。结果表明，菌株JK-SH007具有明显的产嗜铁素能力，其嗜铁素合成相关基因cepR大小为720 bp，与B.pyrrocinia（EU034001）的亲缘关系最近，同源性为99%，两者序列相似性为97%，13个位点出现SNP；另外菌株JK-SH007 cepR基因编码的氨基酸序列有3个氨基酸发生了替换，两者一致性为97%。该菌产嗜铁素最优培养时间是15 h、pH 8、转速200 r/min、最佳碳源和氮源分别是甘油和氯化铵；PB试验筛选出影响该菌株产嗜铁素的关键性因素分别是pH、加碳量、加氮量；CCD试验结果显示，pH和加氮量的交互作用较明显；最终采用Design-Expert软件分析出菌株JK-SH007产嗜铁素最佳方案为碳源加入量15.00 g/L、氮源加入量10.50 g/L、温度30℃、pH 7.36，优化后菌株产嗜铁素能力由18.59提升到37.86，响应面优化产嗜铁素条件的效果是显著的，嗜铁素产量得到明显提高。     

Insights into the virulence‐related genes of Edwardsiella tarda isolated from turbot in Europe: genetic homogeneity and evidence for vibrioferrin production

Edwardsiella tarda has long been known as a pathogen that causes severe economic losses in aquaculture industry. Insights gained on E. tarda pathogenesis may prove useful in the development of new methods for the treatment of infections as well as preventive measures against future outbreaks. In this report, we have established the correlation between the presence of virulence genes, related with three aspects typically involved in bacterial pathogenesis (chondroitinase activity, quorum sensing and siderophore‐mediated ferric uptake systems), in the genome of E. tarda strains isolated from turbot in Europe and their phenotypic traits. A total of 8 genes were tested by PCR for their presence in 73 E. tarda isolates. High homogeneity was observed in the presence/absence pattern of all the strains. Positive results in the amplification of virulence‐related genes were correlated with the detection of chondroitinase activity in agar plates, in vivo AHL production during fish infection and determination of type of siderophore produced by E. tarda. To the best of our knowledge, this is the first study carried out with European strains on potential virulence factors. Furthermore, we demonstrated for the first time that E. tarda produces the siderophore vibrioferrin.     

Study the Effects of Siderophore-Producing Bacteria on Zinc and Phosphorous Nutrition of Canola and Maize Plants

Plant growth-promoting rhizobacteria (PGPR) are soil bacteria that are able to colonize rhizosphere and to enhance plant growth by means of a wide variety of mechanisms. In the present study, Myristica yunnanensis and Stenotrophomonas chelatiphaga strains were recognized as new records in Iran flora. According to the results, these strains significantly affected plants’ zinc and phosphorous contents which could be due to the production of phytosiderophore. Siderophore-producing bacteria increased canola zinc (Zn) content as strategy-I plant, while in maize, it can be said that probably the effect of phytosiderophore produced by plant on increasing root and shoot Zn content was more than siderophore produced by bacteria. These isolates could be used as bio-input for improving the plant productivity as a substitute to chemical fertilizers and also to correct the nutrient deficiencies in canola and maize for sustainable agriculture.     

洋葱伯克霍尔德式菌CAS19产嗜铁素条件的研究

采用光谱吸收法,对一株分离自土壤的嗜铁细菌洋葱伯克霍尔德式菌Burkholderia cepacia CAS19产嗜铁素的条件进行研究。结果表明,MSA培养基最适于CAS19产嗜铁素,并且在320nm处有一个嗜铁素特异吸收峰;当铁离子浓度大于1μmol/L时,几乎完全抑制CAS19嗜铁素的产生;CAS19产嗜铁素的最适条件为:以蔗糖(sucrose)为C源,以脯氨酸(Pro)为N源,C/N比为10∶1,pH值为7.5,温度为30℃,通气量为20mL/250mL。     

高产嗜铁素恶臭假单胞菌A3菌株的鉴定及其对黄瓜的促生作用

从大棚蔬菜根际土中分离到一株嗜铁素高产菌株A3,铬天青（CAS）法定量检测其嗜铁素相对含量达93.40%,Shenkers实验确定为羧酸型嗜铁素。在不同底物诱导下,该菌株可不同程度地产生吲哚乙酸（IAA）及1-氨基环丙烷-1-羧酸（ACC）脱氨酶,并具有一定的溶磷能力。根据形态特征、生理生化、API系统及16S rRNA基因序列分析,将菌株A3鉴定为恶臭假单胞菌（Pseudomonas putida）。在缺铁Hoagland营养液中添加难溶性铁及菌株A3嗜铁素发酵滤液的处理组,能够显著提高黄瓜幼苗的株高、根长、叶长、鲜重及叶绿素含量,表明菌株A3产生的嗜铁素在低铁条件下对黄瓜幼苗具有促生作用。     

贝莱斯芽胞杆菌Bacillus velezensis YL2021嗜铁素合成基因dhbC的功能研究

贝莱斯芽胞杆菌Bacillus velezensis YL2021是一株对多种病原细菌均有良好防治效果的生防菌,基因组中含有完整的儿茶酚型（2,3-Dihydroxybenzoate,DHB）嗜铁素合成基因簇。为了探明贝莱斯芽胞杆菌YL2021嗜铁素的功能,本研究以嗜铁素合成基因dhbC为对象,构建重组质粒pMD19-dhbc（cm）,利用同源重组技术获得突变株ΔdhbC。生防相关性状研究结果表明,与野生型菌株YL2021相比,突变株ΔdhbC泳动能力和生物膜形成能力明显下降,但是群集运动能力未发生改变。在营养丰富的LB培养基中,野生型菌株YL2021和突变株ΔdhbC均不产生嗜铁素,生长能力未发生改变,室内抑菌能力相当;但在缺铁M9培养基中,野生型菌株YL2021能产生儿茶酚型嗜铁素,生长缓慢,对供试细菌有较强的抑菌作用,突变株ΔdhbC不能产生嗜铁素,生长能力明显下降,完全丧失抑菌能力。本文结果表明,缺铁条件下,dhbC基因是贝莱斯芽胞杆菌YL2021嗜铁素生物合成的关键基因,嗜铁素是菌株YL2021发挥生防作用的重要抑菌物质。     

Characterization of bacterial isolates from rotting potato tuber tissue showing antagonism to Dickeya sp. biovar 3 in vitro and in planta

Possibilities for biocontrol of biovar 3 Dickeya sp. in potato were investigated, using bacteria from rotting potato tissue isolated by dilution plating on nonselective agar media. In a plate assay, 649 isolates were screened for antibiosis against Dickeya sp. IPO2222 and for the production of siderophores. Forty‐one isolates (6·4%) produced antibiotics and 112 isolates (17·3%) produced siderophores. A selection of 41 antibiotic‐producing isolates and 41 siderophore‐producing isolates were tested in a potato slice assay for control of the Dickeya sp. Isolates able to reduce rotting of potato tuber tissue by at least 50% of the control were selected. Isolates were characterized by 16S rDNA analysis as Bacillus, Pseudomonas, Rhodococcus, Serratia, Obesumbacterium and Lysinibacillus genera. Twenty‐three isolates belonging to different species and genera, 13 producing antibiotics and 10 producing siderophores, were further characterized by testing acyl‐homoserine lactone (AHL) production, quorum quenching, motility, biosurfactant production, growth at low (4·0) and high (10·0) pH, growth at 10°C under aerobic and anaerobic conditions and auxin production. In replicated greenhouse experiments, four selected antagonists based on the in vitro tests were tested in planta using wounded or intact minitubers of cv. Kondor subsequently inoculated by vacuum infiltration with an antagonist and a GFP (green fluorescent protein)‐tagged biovar 3 Dickeya sp. strain. A potato endophyte A30, characterized as S. plymuthica, protected potato plants by reducing blackleg development by 100% and colonization of stems by Dickeya sp. by 97%. The potential use of S. plymuthica A30 for the biocontrol of Dickeya sp. is discussed.     

出芽短梗霉及其生物产品研究进展

出芽短梗霉是一类具有典型细胞多形性的腐生真菌,不同的出芽短梗霉能产生胞外多聚糖类、胞外酶类及黑色素、聚苹果酸、嗜铁素等发酵产物,可广泛应用于医药、食品、生物防治、化妆品和烟草工业等众多领域。本文综述了出芽短梗霉及其生物产品的研究进展,展望今后通过全基因测序,找到更多出芽短梗霉的新基因与生物产品。