胞外多糖产生菌的筛选鉴定及其促生改土作用

【背景】一些微生物具有较强的产胞外多糖潜力，在改良盐碱土壤、促进作物生长方面潜力巨大。【目的】筛选耐盐碱且产胞外多糖的微生物，为开发具有盐碱土壤改良效果的菌剂提供菌种资源。【方法】从滨海盐碱植物根际土中筛选可在盐碱土壤中增殖、产胞外多糖、解有机磷和钾等能力的微生物菌株，并通过形态、生理生化、基于16S rRNA基因序列和gyrB基因的分子鉴定确定菌株类别，分析该菌株的生长、产胞外多糖特性受盐碱胁迫的影响，考察该菌对盐碱土壤不同粒径团聚体比例的影响，并结合盐碱土壤番茄种植试验考察对植物生长指标和土壤指标的影响。【结果】从727株滨海盐碱土壤菌株中筛选出一株产胞外多糖、具有较强盐碱土壤增殖能力且能解有机磷和钾的芽孢杆菌GBW HF-98，确定该菌为枯草芽孢杆菌沙漠亚种(Bacillus subtilis subsp. inaquosorum)。该菌可耐受pH值达10.0和NaCl浓度达110 g/L，在改善轻和中盐度土壤中不同粒径团聚体比例的效果较为显著。该菌的高剂量浓度T2组，在中度盐碱土壤的番茄种植试验中，与对照相比显著增加了壮苗指数、根干重、全株干重、茎粗和株高等指标，增幅分别为33.8%、59.3%、37.2%、12.3%和15.6% (P<0.05)；显著降低pH、全盐含量和土壤容重，降幅分别为8.9%、27.9%和17.9%；显著提升土壤速效磷和速效钾指标，增幅分别为36.0%和17.4% (P<0.05)。【结论】GBW HF-98菌株具有较强的胞外多糖产生能力，在中度盐碱土壤中促进番茄生长和改良土壤的效果显著，可用于盐碱土壤改良菌剂的研制。

Screening and identification of extracellular polysaccharide-producing strain and the influence on soil quality and crop growth

Background] Some microorganisms, with high production of extracellular polysaccharide, can help improve saline-alkali soil and promote crop growth. Objective] To screen saline-alkali-tolerant and extracellular polysaccharide-producing microorganisms for the development of microbial agents which can improve saline-alkali soil. Methods] We screened strains which reproduce in saline-alkali soil, produce extracellular polysaccharide, and have the ability to solubilize phosphate and release potassium from rhizosphere soil of plants in coastal saline-alkali area. The eligible strain was identified based on morphological observation, physiological and biochemical indexes, 16S rRNA gene and gyrB gene sequencing. Then we analyzed growth of the strain and the production of extracellular polysaccharide under saline-alkali stress. In addition, the influence of the strain on the proportion of aggregates with different particle sizes in saline-alkali soil was investigated, and the effect on growth indexes of tomato in saline-alkali soil and soil indexes was examined. Results] From 727 strains in coastal saline-alkali soil, strain GBW HF-98 was screened out, which, with strong reproductive ability in saline-alkali soil, produced extracellular polysaccharide and had the ability to solubilize phosphate and release potassium. The strain was identified as Bacillus subtilis subsp. inaquosorum and it can tolerate pH 10.0 stress and NaCl concentration of up to 110 g/L. It significantly improved the proportion of aggregates with different particle sizes in soil with mild and moderate salinity. The high dose of this strain (T2 group) increased the strong seedling index, root dry weight, dry weight of whole plant, stem diameter, and plant height of tomato in soil with moderate salinity by 33.8%, 59.3%, 37.2%, 12.3%, and 15.6%, respectively, as compared with the control (P<0.05). Moreover, it significantly reduced pH, total salt content, and soil bulk density by 8.9%, 27.9%, and 17.9%, respectively, and significantly raised soil available phosphorus content and available potassium content by 36.0% and 17.4%, separately (P<0.05).Conclusion] GBW HF-98, with high production of extracellular polysaccharide, can remarkably promote the growth of tomato in moderately saline-alkali soil and improve the soil. Thus, it can be used for the development of microbial agents for the improvement of saline-alkali soil.