一株吡啶降解菌Pseudomonas sp. ZX08的生物膜形成特性及影响因素

Characteristics and influencing factors of biofilm formation by a pyridine-degrading bacterium Pseudomonas sp. ZX08

摘要:

【背景】煤化工企业排放的废水中含有大量难降解、高毒性的有机污染物，采用以高效降解菌为基础的生物强化技术对其进行处理，是一种经济可行的策略；而促进高效降解菌在载体材料表面的生物膜形成，有助于提升生物膜法废水处理系统的效能。【目的】探究一株吡啶高效降解菌Pseudomonas sp. ZX08的生物膜形成过程和特性，识别不同的环境因子如温度、pH、Na+、K+、Ca2+、Mg2+等对其生物膜形成的影响规律，为实现人工调控其在实际废水处理系统中的成膜过程提供理论依据。【方法】采用改良的微孔板生物膜培养与定量方法，以单因子影响实验测定不同条件下菌株在12孔板内的生物膜形成量和浮游态细菌量；采用激光共聚焦显微镜(confocal laser scanning microscope，CLSM)观察和分析生物膜的结构特征。【结果】Pseudomonas sp. ZX08菌株具有良好的吡啶降解性能，且生物膜形成能力较强，CLSM观察到其在载体表面形成的生物膜可达40?50 mm；生物膜外层的活细胞比例更高，分泌的胞外蛋白也更多。ZX08菌株的生物膜形成量具有明显的周期性变化特征，12 h、48 h的生物膜量是相对峰值。ZX08生物膜形成的最适温度是25 °C，最适pH范围是7.0?9.0；较高浓度的NaCl (>0.6 mol/L)和KCl (>0.4 mol/L)均对ZX08的生物膜形成有显著的抑制作用；一定范围内(0?16 mmol/L) Ca2+浓度的提高可以促进ZX08在12孔板底部固-液界面生物膜的形成，浓度更高时则显著抑制生物膜的形成；一定范围内(0?16 mmol/L) Mg2+浓度的提高对ZX08生物膜形成有促进作用，但促进幅度不大。【结论】吡啶降解菌Pseudomonas sp. ZX08的生物膜形成能力较强，未来在实际废水处理系统中应用时需要综合考虑各种环境因子对其生物膜形成的影响。

Abstract:

[Background] The wastewater discharged by coal chemical industries contains a large number of refractory and highly toxic organic pollutants. It is an economically feasible strategy to treat the wastewater with bioaugmentation technology based on efficient degrading bacteria. Promoting the biofilm formation of degrading bacteria is proved to be beneficial to the performance of the biofilm wastewater treatment system. [Objective] To investigate the biofilm formation process and characteristics of a pyridine-degrading bacterium Pseudomonas sp. ZX08, and to identify the influence of different environmental factors such as temperature, pH, Na+, K+, Ca2+, Mg2+ on biofilm formation, and finally to provide references for regulating biofilm formation in wastewater treatment systems. [Methods] A modified microtiter dish biofilm formation assay was used to determine the biofilm formation and the planktonic bacteria growth in the 12-well plate under different conditions; the structural characteristics of biofilm was observed and analyzed by a confocal laser scanning microscope (CLSM). [Results] Pseudomonas sp. ZX08 showed good pyridine-degrading performance and biofilm-forming abilities. According to the CLSM analysis, the thickness of its biofilms formed at the surface reached 40?50 mm, and the proportion of live cells and protein/cell ratio were higher in the outer layer of the biofilms. A periodic variation was observed in the biofilm formation process in 72 h, and the biofilm biomass at 12 h and 48 h were relative peaks. The optimum temperature for ZX08 biofilm formation was 25 °C, and the optimum pH range was 7.0?9.0. Higher concentrations of NaCl (>0.6 mol/L) and KCl (>0.4 mol/L) significantly inhibited the biofilm formation of ZX08. Within a certain range (0?16 mmol/L), the increase of Ca2+ concentration could promote the biofilm formation at the solid-liquid interface of the 12-well plate bottom. Adding Mg2+ ranged from 0?16 mmol/L also resulted in a slight increase in the biofilm formation of ZX08. [Conclusion] The pyridine-degrading bacterium Pseudomonas sp. ZX08 can form thick and stable biofilms, and it needs to comprehensively consider the influence of various environmental factors on its biofilm formation in future applications.