解淀粉芽胞杆菌PHODB35的溶磷特性及其对番茄的促生作用

【目的】从种植番茄的根围土壤中筛选高效溶磷细菌,为减施化学肥料和开发微生物肥料提供溶磷菌种资源,并初步探索其促生机制。【方法】采用无机磷培养基利用梯度稀释涂布法从土壤中分离筛选促生菌株,通过形态特征、16S rRNA和gyrB基因序列分析对优良促生菌株进行鉴定,并分别利用正交试验和单因素试验分析环境因子和营养因子对其溶磷效果的影响,进一步利用HPLC-MS并结合相应有机酸的标准物质,明确优良促生菌株产生的有机酸种类;盆栽试验测定接菌处理后番茄株高、地上鲜重、地下鲜重、基质和植株有效磷含量评价菌株对番茄的促生作用。【结果】筛选到1株优良的促生菌株,命名为PHODB35,鉴定其为解淀粉芽胞杆菌(Bacillus amyloliquefaciens)。对环境因子的正交试验结果表明,菌株PHODB35最佳溶磷条件为pH 7.0,温度为30°C,接种量为5%;对营养因子的单因素试验结果表明,该菌株以葡萄糖为碳源、硫酸铵为氮源、磷酸钙为磷源时,解磷效果最好,有效磷浓度为88.77mg/L。明确了菌株PHODB35产生的有机酸为葡萄糖酸。盆栽实验结果表明,菌株PHODB35对番茄幼苗有明显的促生作用,与空白对照相比,施用菌株后对株高、地上鲜重、地下鲜重、基质和植株有效磷含量分别增加28.21%、22.59%、113.06%、45.08%和16.24%,表明菌株PHODB35具有一定的肥效功能,可用于促生菌剂的研制。【结论】筛选到具有促生能力的解磷细菌,为进一步开发研制番茄促生菌剂或微生物有机肥提供资源,为菌株PHODB35在农业生产中的应用提供了理论依据和实验基础。

Unlocking the bacterial contact-dependent antibacterial activity to engineer a biocontrol alliance of two species from natural incompatibility to artificial compatibility

Plant growth-promoting rhizobacteria(PGPR)contain various biocontrol bacteria with broad-spectrum antimicrobial activity,and their single species has been extensively applied to control crop diseases.The development of complex biocontrol community by mixing two or more PGPR members together is a promising strategy to enlarge the efficacy and scope of biocontrol.However,an effective method to assess the natural compatibility of PGPR members has not yet been established to date.Here,we developed such a tool by using the bacterial contactdependent antibacterial activity(CDAA)as a probe.We showed that the CDAA events are common in two-species interactions in the four selected representative PGPRs,represented by the incompatible interaction of Lysobacter enzymogenes strain OH11(OH11)and Lysobacter antibioticus strain OH13(OH13).We further showed that the CDAA between OH11 and OH13 is jointly controlled by a contact-dependent killing device,called the type IV secretion system(T4SS).By deleting the respective T4SS synthesis genes,the T4SS in both strains was co-inactivated and this step unlocked their natural CDAA,resulting in an engineered,compatible mutant alliance that co-displayed antibacterial and antifungal activity.Therefore,this study reveals that releasing bacterial CDAA is effective to rationally engineer the biocontrol community.