干湿交替循环频率对生物膜特征及其微生物群落的影响

Effects of alternate drying-wetting cycles on biofilm characteristics and their microbial communities.

为研究干湿交替循环下生物膜的抗性机制,以天然水体生物膜为研究对象,基于室内控制实验,通过16S rRNA高通量测序和激光共聚焦显微成像等技术,探究干湿交替循环对生物膜形态结构及其微生物种群结构、多样性和功能的影响.结果表明,随着干湿交替循环频率从一轮(C1)增加到五轮(C5),生物膜厚度从9.10减小到6.46µm,胞外聚合物含量从2.64μm^(3)/μm^(3)(对照)减少到1.90μm^(3)/μm^(3)(C1),再增加到4.41μm^(3)/μm^(3)(C3),随后减少到1.54μm^(3)/μm^(3)(C5,P=0.004),活/死菌比例则从2.52(C1)增加到3.60(C3)再显著减少到0.72(C5,P=0.009),而比表面积和粗糙度系数无显著变化.与对照相比,干湿交替循环下生物膜内微生物群落丰富度和多样性下降,指示物种发生改变.当干湿交替循环的频率超过生物膜耐受程度(C5)时,生物膜内优势菌由变形菌转变为与蓝藻相关的菌群,且生物膜功能由化能异养转变为光合自养.可见,不同干湿交替循环频率下生物膜形态结构和微生物种群结构不同,且在干湿交替循环频率较低时生物膜内微生物群落的生存策略表现为抵抗力,频率较高时表现为恢复力.

The periphytic biofilm was sampled in natural environment and cultivated under indoor controlled conditions to clarify the biofilm resistance mechanisms under the influence of alternate drying and wetting cycles.The morphology,microbial community structure,diversity and function of natural biofilms were examined using 16S rRNA gene high throughput sequencing and confocal laser scanning microscopy.The results showed that biofilm thickness was reduced from 9.10 to 6.46µm with the increase of alternate drying-wetting cycles from one(C1)to five(C5).The extracellular polymer content decreased from 2.64μm^(3)/μm^(3)(control)to 1.9μm^(3)/μm^(3)(C1),and then increased from 4.41μm^(3)/μm^(3)(C3)to 1.54μm^(3)/μm^(3)(C5,P=0.004).The ratio of live/dead bacteria increased from 2.52(C1)to 3.60(C3),and then decreased to 0.72(C5,P=0.009).However,the changes in surface area to volume ration and roughness coefficient with the alternate drying and wetting cycles were not significant compared to the control.In contrast to the control,the richness and diversity of the microbial community decreased and the indicator species changed when biofilm exposed to alternate drying and wetting cycles.The dominant bacteria in biofilm shifted from Proteobacteria to Cyanobacteria-related flora when the alternate drying and wetting cycles reached to five(C5).Moreover,functional groups associated with photoautotrophy became the most abundant.Therefore,biofilm morphology and microbial community structure were associated with the alternate drying and wetting cycles.Microbial communities exhibited high degrees of resistance under lower alternate drying and wetting cycles,whereas showed high degrees of resilience to increased alternate drying and wetting cycles.