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塑料的广泛使用使得进入环境的塑料越来越多,随着时间的推移逐渐在水体中积累[1]。微塑料因其尺寸小、比表面积大、疏水性高等表面特性,使得微生物更容易黏附在其表面而形成异质性结构的生物膜[2]。在生物膜形成过程中,较高的细菌密度会产生能够与受体蛋白做出有效反应的群体感应(quorum sensing)信号[3]。群体感应是细菌达到一定浓度阈值时通过信号分子分泌、识别,调节基因表达、协调菌群行为的一种细胞交流机制[4]。这种机制赋予细菌一系列社会性能力,包括生物发光、生物膜形成[5]、基因水平转移[6-7]等。群体感应通过多个“信号通路”调节胞外多聚物的产生,从而控制生物膜的形成[8]。生物膜的形成与群体感应有着较强的关联性。微塑料在水环境中大量存在具有时间尺度的持久性、空间尺度的高传输性,还可通过食物链在生态圈中传递的特点,其表面的生物膜上的生态位点富集了很多潜在的致病菌[9]。研究微塑料生物膜群体感应信号分子分泌特征以及信号分子对生物膜形成的调节作用,为探究微塑料生物膜形成过程中群体感应的调控作用机制提供研究基础,同时为治理水环境中微塑料污染提供一种新的思路。
厚壁菌门在微塑料生物膜中常被发现[10]。从属于厚壁菌门的枯草芽孢杆菌能够分泌产生酰基高丝氨酸内酯(AHLs)类群体感应信号分子[11],该类信号分子广泛存在于微生物界的群体中。目前,对生物膜中AHLs类群体感应信号分子鉴定方法通常包括传统的薄层色谱法[12]、气相色谱质谱法[13]。因液相色谱-串联质谱法检测快速、准确性和灵敏度高等优点,近年来被多项研究应用于AHLs的定性与定量[14-17]。由于生物膜产生的信号分子浓度往往低于仪器检出限,需对样品进行浓缩富集。常用的富集方法包括固相萃取(SPE)[18]、液液萃取(LLE)[19]、固相萃取串联液相萃取(SPE-LLE)[20]。SPE和SPE-LLE通常适用于基质影响较大的环境样品[15],由于培养体系中枯草芽孢杆菌生物膜基质干扰相对较小,本研究选用萃取过程相对简单和经济的LLE方法。
本研究针对生物膜上常检出的3-oxo-C6-HSL 、C6-HSL和3-oxo-C8-HSL等 11种AHLs类信号分子 [20-22],采用LLE作为样品的前处理方法,通过对萃取方式和萃取液进行优化来提高微塑料枯草芽孢杆菌生物膜中AHLs回收率,基于超高效液相色谱-串联三重四极杆质谱(UPLC-MS/MS)仪器分析平台,优化色谱质谱分析条件,建立一种快速、准确的微塑料生物膜中AHLs类群体感应信号分子检测方法。使用所建立的方法来测定在生活生产使用最多且水环境中常被检出的聚丙烯(polypropylene,PP)、聚乙烯(polyethylene,PE)、聚苯乙烯(polystyrene,PS)的3种微塑料[23]上生物膜群体感应分泌的11种AHLs类信号分子,并研究其分泌特征。同时,添加外源信号分子来初步探究群体感应信号分子分泌量对生物膜成膜的影响。研究多种AHLs类信号分子化合物的同时定性与定量分析,能为微生物群体感应的进一步研究提供有效且便利的分析方法。
微塑料生物膜11种AHLs类群体感应信号分子测定及其分泌特征
Determination and secretion characteristics of 11 N-acyl-homoserine lactones signal molecules of quorum sensing in microplastic biofilms
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摘要: 为研究微塑料生物膜的群体感应效应,利用液液萃取和超高效液相色谱-串联质谱技术,建立了微塑料上枯草芽孢杆菌生物膜分泌的11种酰基高丝氨酸内酯(AHLs)类群体感应信号分子前处理和仪器分析方法。优化后的前处理方法采用酸化的乙酸乙酯(0.01%冰乙酸,V/V)对微塑料生物膜样品中AHLs类信号分子进行萃取,萃取方式采用冰浴超声。微塑料生物膜中AHLs回收率为50.6%—128.1%,相对标准偏差(n = 3)为0.2%—10.6%。对色谱和质谱条件进行优化,11种AHLs在0.5—50 μg·L−1范围内呈良好的线性关系(R2 > 0.995),检出限为0.005—0.01 μg·L−1,定量限为0.01—0.02 μg·L−1。本方法具有快速、准确、灵敏度高等优点。对聚丙烯、聚乙烯、聚苯乙烯等3种微塑料上枯草芽孢杆菌生物膜中11种AHLs分析结果表明,C8-HSL、C12-HSL和3-oxo-C10-HSL在3种微塑料生物膜中均被检出;C12-HSL的产生量最高,且在聚乙烯表面生物膜中含量最高达34 ng·g−1。通过添加外源信号分子研究表明,AHLs分子浓度增加会促进微塑料生物膜形成。
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关键词:
- 超高效液相色谱-串联质谱 /
- 生物膜 /
- 群体感应 /
- 酰基高丝氨酸内酯 /
- 微塑料
Abstract: In order to study the quorum sensing effect of biofilms on microplastics, a pretreatment and instrumental analysis method for 11 N-acyl-homoserine lactones (AHLs) secreted by Bacillus subtilis biofilms on microplastics was established by liquid-liquid extraction and ultra-performance liquid chromatography-tandem mass spectrometry. The optimized pretreatment method used acidified ethyl acetate (0.01% glacial acetic acid, V/V) to extract AHLs signal molecules from microplastic biofilm samples. The extraction method used ultrasound with ice bath. The recoveries of 11 AHLs in microplastic biofilms ranged from 50.6% to 128.1%, and the relative standard deviations (n = 3) ranged from 0.2% to 10.6%. After the optimization for chromatographic and mass spectrometry condition, the linearities of 11 AHLs were good in the range of 0.5—50 μg·L−1 (R2 > 0.995), the limits of detection were in the range of 0.005—0.01 μg·L−1, and the limits of quantification were in the range of 0.01—0.02 μg·L−1. The method is rapid and accurate, and has high sensitivity. The quantitative analysis for 11 AHLs in Bacillus subtilis biofilms on polypropylene, polyethylene and polystyrene showed that C8-HSL, C12-HSL and 3-oxo-C10-HSL were all detected in the three types of microplastic biofilms; the production amount of C12-HSL was the highest, and was up to 34 ng·g−1 in polyethylene biofilm. The result from the addition of exogenous AHLs indicated the increasing concentrations of AHLs can promote the biofilm formation on microplastics.-
Key words:
- UPLC-MS/MS /
- biofilm /
- quorum sensing /
- AHLs /
- microplastics
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表 1 12种AHLs类信号分子的质谱条件
Table 1. Analysis parameters of 12 AHLs for mass spectrometry
化合物
Compounds母离子(m/z)
Parents ion子离子(m/z)
Daughter ion锥孔电压/ V
Cone碰撞能量/eV
Collision energy3-oxo-C6-HSL 214 102.0*,111 20 10 C6-HSL 200.1 102.0*,99 20 10 3- oxo-C8-HSL 242.2 102.0*,140.9 20 15 C7-HSL 214.3 102.0*,111.3 20 15 C8-HSL 228.2 102.0*,126.6 20 15 3-oxo-C10-HSL 270.2 102.0*,169 20 15 C10-HSL 256 102.0*,155 20 15 3-oxo-C12-HSL 298 102.0*,197 20 15 3-OH-C12-HSL 300.4 102.0*,199.4 20 15 C12-HSL 284.3 102.0*,183.1 20 15 3-oxo-C14-HSL 326.4 102.0*,102 20 15 C14-HSL 312 102.0*,211 20 15 *为定量离子. *Ions are quantitative ions. 表 2 11种AHLs信号分子的线性关系、检出限、定量限
Table 2. The linear regression equation,limit of detection,limit of quantitation of 11 AHLs
化合物
Compounds线性回归方程
Linear regression equations回归系数
Regression coefficient R2检出限/ (μg·L-1)
Limit of detection定量限/ (μg·L-1)
Limit of quantitation3-oxo-C6-HSL y=3.53x+0.44 0.9996 0.005 0.02 C6-HSL y=1.38x+0.09 0.9998 0.01 0.02 3-oxo-C8-HSL y=5.17x+0.31 0.9992 0.005 0.01 C8-HSL y=2.31x+0.57 0.9989 0.005 0.01 3-oxo-C10-HSL y=2.77x+0.10 0.9991 0.005 0.01 C10-HSL y=2.86x+0.80 0.9987 0.005 0.01 3-oxo-C12-HSL y=6.32x+0.44 0.9986 0.005 0.01 3-OH-C12-HSL y=1.38x+0.21 0.9966 0.005 0.01 C12-HSL y=2.44x+0.70 0.9971 0.005 0.01 3-oxo-C14-HSL y=3.70x+0.39 0.9955 0.005 0.01 C14-HSL y=3.27x+0.36 0.9987 0.005 0.02 表 3 11种AHLs的加标回收率和相对标准偏差(n = 3)
Table 3. Recoveries and relative standard deviations of 11 AHLs(n = 3)
化合物
Compounds添加浓度2 μg·L−1 添加浓度5 μg·L−1 添加浓度10 μg·L−1 平均回收率/%
Mean recoveryRSD/% 平均回收率/ %
Mean recoveryRSD/ % 平均回收率/%
Mean recoveryRSD /% 3-oxo-C6-HSL 54.2 1.3 57.2 0.9 60.1 1.5 C6-HSL 128.1 10.6 101.2 2.7 117.1 6.6 3-oxo-C8-HSL 93.0 5.5 52.6 1.6 90.0 1.2 C8-HSL 119.7 5.8 109.6 5.2 118.8 0.5 3-oxo-C10-HSL 99.5 1.6 101.3 5.2 90.2 3.4 C10-HSL 108.9 6.2 60.7 1.3 86.0 0.3 3-oxo-C12-HSL 78.0 4.3 50.6 1.6 79.0 0.4 3-OH-C12-HSL 65.1 2.3 54.2 1.4 64.0 0.8 C12-HSL 65.1 2.5 64.6 0.9 65.2 1.0 3-oxo-C14-HSL 55.3 0.2 58.4 1.6 56.5 0.5 C14-HSL 73.7 2.3 57.2 2.0 66.8 0.8 -
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