Mn^(2+)促进Bacillus altitudinis LZP02生物膜形成

【目的】Bacillus altitudinis LZP02是一株水稻根际促生菌(PGPR),能定殖于水稻根部,形成生物膜,且Mn^(2+)对LZP02菌株生物膜形成具有促进作用,但调控机制尚不明确,旨在探究Mn^(2+)对LZP02菌株生物膜形成的促进机制。【方法】采用结晶紫染色法进行生物膜定量分析、蒽酮-硫酸法测定胞外多糖产量、扫描电镜(SEM)观察LZP02菌株在水稻根际定殖情况、转录组学测序技术分析差异表达基因(DEGs)。【结果】添加4 mmol/L Mn^(2+)和8 mmol/L Mn^(2+)显著提高了LZP02菌株的成膜能力和胞外多糖产量,扫描电镜发现4 mmol/L Mn^(2+)和8 mmol/L Mn^(2+)提高了LZP02菌株在水稻根际的定殖能力,随着Mn^(2+)浓度的增加,DEGs数量显著增多,其主要富集在芽孢形成、毒素代谢途径和双组分系统中。1 mmol/L Mn^(2+)和4 mmol/L Mn^(2+)处理组发现skf操纵子中基因的表达均上调。扫描电镜观察发现在1 mmol/L Mn^(2+)和4 mmol/L Mn^(2+)处理组中LZP02菌体存在损伤。4 mmol/L Mn^(2+)处理组双组分系统中KinE和Spo0A基因均显著上调。【结论】Mn^(2+)通过“嗜食同类”和双组分系统中KinE基因激活Spo0A~P提高了菌株LZP02的成膜能力。

环境条件对Bacillus altitudinis LZP02生物膜形成的影响

Bacillus altitudinis LZP02是一株水稻根际促生菌,可在水稻根际定殖,形成生物膜。为研究Bacillus altitudinis LZP02生物膜的形成情况,在不同培养条件下,通过96孔微量平板法观察生物膜形成,并采用结晶紫染色法对其进行定量。结果表明,B.altitudinis LZP02在培养基表面形成稳定的生物膜结构,具有良好的生物膜形成能力。其形成生物膜的最适温度为30℃,在25℃只形成少量生物膜,说明低温降低了B.altitudinis LZP02生物膜形成能力;在pH值为4~10时均能形成生物膜,pH值为7.0时生物膜形成能力最强。Ca^(2+)对B.altitudinis LZP02生物膜形成没有明显的影响,Fe^(2+)、Fe^(3+)、Mg^(2+)、K^(+)、Na^(+)、Zn^(2+)、Cu^(2+)可以抑制B.altitudinis LZP02生物膜的形成,Mn^(2+)能够促进B.altitudinis LZP02生物膜的形成。该研究结果为B.altitudinis LZP02的进一步开发利用提供了重要参考,也为深入探究B.altitudinis LZP02生物膜形成机制提供了现实依据。

Production,purification and activity evaluation of three novel antioxidant peptides obtained from grass carp(Ctenopharyngodon idella)scale waste by microbial protease BaApr1 hydrolysis

In this study,an alkaline protease BaApr1 from the Bacillus altitudinis W3 was chosen to hydrolysis grass carp(Ctenopharyngodon idella)scales.The hydrolysate of alkaline protease BaApr1 exhibited the best antioxidant activity compared to other protease hydrolysates.The optimal hydrolysis conditions for BaApr1 were an enzyme dosage of 1250 U/g,a hydrolysis time of 7 h,a pH of 9.5 and a temperature of 50℃.Three novel peptides were purified using ultrafiltration,anion exchange chromatography,gel filtration chromatography and ultra-performance liquid chromatography,and their sequences were identified as Tyr-Val-Gln-Ala-Gly-Ala-Ala-Gly-Ala-Ala-Ala-His(SHP2),Val-Lys-Leu-Tyr-Val-Leu-Leu-Val-Pro(SHP4),and Val-Gln-Val-Leu-Ala-Gly-Pro-Val-Val-Lys-Leu-Tyr(SHP5)with molecular weights of 1086.53 Da,1043.69 Da and 1285.79 Da,respectively.Among them,SHP2 exhibited the highest scavenging activity on DPPH;(EC_(50)4.08 mg/mL),ABTS+;(EC_(50)0.23 mg/mL)and HO;(EC_(50)2.78 mg/mL),and the strongest reducing power.Additionally,SHP5 can significantly inhibit lipid peroxidation in the linoleic acid system.In conclusion,three peptides isolated from scales of hydrolysate of grass carp showed great antioxidant activity and might be used as potential food ingredients and pharmaceuticals.