概要

通过真空辅助吸附剂提取从人类相关样品中捕获活性产生的微生物挥发性有机化合物

Published: June 01, 2022
doi:

概要

该协议描述了使用真空辅助吸附剂提取方法从生物样品中提取挥发性有机化合物,使用Entech样品制备导轨进行气相色谱结合质谱分析以及数据分析。它还描述了生物样品的培养和稳定同位素探测。

Abstract

来自生物样品的挥发性有机化合物(VOC)来源不明。挥发性有机化合物可能来自宿主或宿主微生物群落内的不同生物体。为了解开微生物VOC的起源,对 金黄色葡萄球菌、铜绿假单胞菌 鲍曼不动杆菌的细菌单培养物和共培养物进行了挥发性顶空分析,并在粪便、唾液、污水和痰液的生物样品中进行了稳定同位素探测。单培养和共培养用于鉴定单个细菌物种的挥发性产生,或与稳定同位素探测结合使用,以鉴定生物样品中微生物的活性代谢。

采用真空辅助吸附剂萃取(VASE)提取VOCs。VASE是一种易于使用,商业化,无溶剂的顶空提取方法,用于半挥发性和挥发性化合物。与其他提取选项(如 叔丁基化和固相微萃取)相比,提取过程中使用的溶剂和近真空条件使得开发方法相对容易和快速。此处描述的工作流程用于识别来自单一培养和共培养物的特定易失性特征。此外,对人类相关生物样品的稳定同位素探测的分析确定了通常或独特生产的VOC。本文结合活性微生物培养物的稳定同位素探测,提出了VASTE的一般工作流程和实验注意事项。

Introduction

挥发性有机化合物(VOCs)在细菌检测和鉴定方面具有很大的前景,因为它们是从所有生物体中排放的,并且不同的微生物具有独特的VOC特征。挥发性分子已被用作检测各种呼吸道感染的非侵入性测量,包括慢性阻塞性肺病1,尿中的结核病2和呼吸机相关肺炎4,此外还区分囊性纤维化(CF)受试者和健康对照受试者56。挥发性特征甚至已被用于区分CF中的特定病原体感染(金黄色葡萄球菌7铜绿假单胞菌89金黄色葡萄球菌铜绿假单胞菌10)。然而,由于这种生物样品的复杂性,通常很难确定特定挥发性有机化合物的来源。

从多种感染微生物中分离挥发性特征的一种策略是对单培养和共培养11中的微生物进行顶空分析。顶空分析检查排放到样品上方“顶空”中的分析物,而不是嵌入样品本身的分析物。微生物代谢物通常在单一培养物中表征,因为在复杂的临床样品中难以确定微生物代谢物的来源。通过分析来自细菌单培养物的挥发物,微生物 在体外 产生的挥发物类型可能代表其挥发性库的基线。结合细菌培养物, 例如,创建共培养物,并分析产生的挥发性分子可以揭示细菌12之间的相互作用或交叉喂养。

鉴定挥发性分子微生物来源的另一种策略是提供用稳定同位素标记的营养来源。稳定同位素是天然存在的,具有不同数量中子的原子的非放射性形式。自20世纪30年代初以来,一种用于追踪动物活性代谢的策略13中,微生物以标记的营养来源为食,并将稳定同位素纳入其代谢途径。最近,重水(D2O)形式的稳定同位素已被用于鉴定临床CF痰液样本14中代谢活性的金黄色葡萄球菌。在另一个例子中,13个C标记的葡萄糖已被用于证明铜绿假单胞菌Rothia mucilaginosa12的CF临床分离物之间代谢物的交叉喂养。

随着质谱技术的进步,检测挥发性线索的方法已经从定性观察转向更定量的测量。通过使用气相色谱质谱(GC-MS),大多数实验室或临床环境都能够处理生物样品。许多调查挥发性分子的方法已被用于分析样品,例如食品,细菌培养物和其他生物样品,以及空气和水以检测污染。然而,具有高通量的几种常见挥发性取样方法需要溶剂,并且不能以真空萃取提供的优点进行。此外,分析通常需要更大体积或数量(大于0.5 mL)的样品材料1516,171819,尽管这是底物特异性的,需要针对每种样品类型和方法进行优化。

在这里,采用真空辅助吸附剂提取(VASE)然后在GC-MS上进行热解吸,以调查细菌单培养物和共培养物的挥发性分布,并鉴定来自人类粪便,唾液,污水和痰液样品的稳定同位素探测的活性挥发物(图1)。在样品量有限的情况下,从低至15μL的痰中提取VOCs。对人类样品的同位素探测实验需要添加稳定的同位素源,如 13°C葡萄糖和培养基来培养微生物群落的生长。挥发物的活性生产被GC-MS确定为更重的分子。在静态真空下提取挥发性分子能够以更高的灵敏度检测挥发性分子202122

Protocol

1. 顶空吸附笔(HSP)和样品分析注意事项 注意:选择含有吸附剂Tenax TA的HSP是为了捕获各种挥发物。与其他吸附剂相比,Tenax对水的亲和力较低,这使其能够从高湿度样品中捕获更多的VOC。Tenax还具有低水平的杂质,可以调节以重复使用。在GC-MS中安装色谱柱时,还考虑了吸附剂的选择(参见 材料表)。 通过提取具有与样品提取相同的条件提取培养基和/或…

Representative Results

金黄色葡萄球菌、铜绿假单胞菌和鲍曼氏菌的单一和共培养 单一培养和共培养物由细菌种类 金黄色葡萄球菌、铜绿假单胞菌 和 鲍曼氏菌组成。这些是在人类伤口和慢性感染中发现的常见机会性病原体。为了鉴定单培养物和共培养物中存在的挥发性分子,在70°C下以200rpm搅拌进行短的…

Discussion

为了鉴定 体外 培养物和人相关样品中的挥发性产生,对 铜绿假单胞菌,金黄色葡萄球菌 鲍曼氏 菌的单培养物和共培养物进行挥发性分析,并对不同生物样品进行稳定同位素探测。在单培养和共培养物的分析中,通过在70°C下进行短萃取1小时来检测挥发物。 对单一培养和共培养物的挥发性分析允许对单个物种及其与其他物种相互作用期间产生的化合物进行调查。不同文化…

開示

The authors have nothing to disclose.

Acknowledgements

我们感谢希瑟·毛恩(Heather Maughan)和琳达·M·卡利金(Linda M. Kalikin)对这份手稿的精心编辑。这项工作得到了NIH NHLBI的支持(拨款5R01HL136647-04)。

Materials

13C glucose Sigma-Aldrich 389374-1G
2-Stg Diaph Pump Entech Instruments 01-10-20030
20 mL VOA vials Fisher Scientific 5719110
24 mm Black Caps with hole, no septum Entech Instruments 01-39-76044B holds lid liner in place on vial
24 mm vial liner for sorbent pens Entech Instruments SP-L024S allows pens to make a vacuum seal at top of vial
5600 Sorbent pen extraction unit (SPEU) Entech Instruments 5600-SPES 5600 Sorbent Pen Extraction Unit -120 VAC
96-well assay plates Genesee 25-224
Brain Heart Infusion (BHI) media Sigma-Aldrich 53286-500G
ChemStation Stofware Agilent
DB-624 column Agilent 122-1364E 60 m, 0.25 mm ID, 1.40 micron film thickness, in GC-MS
Deuterium oxide Sigma-Aldrich 151882-1L
Dexsi sofware Dexsi (open source)
GC-MS (7890A GC and 5975C inert XL MSD with Triple-Axis Detector) Agilent 7890A GC and 5975C inert XL MSD with triple-axis detector
Headspace Bundle HS-B01, 120VA Entech Instruments SP-HS-B01 Items for running headspace extraction included in bundle
Headspace sorbent pen (HSP) – blank Entech Instruments SP-HS-0
Headspace sorbent pen (HSP) Tenax TA (35/60 Mesh) Entech Instruments SP-HS-T3560
Microcentrifuge tubes (2 mL) VWR 53550-792
O-rings Entech Instruments SP-OR-L024
Sample Preparation Rail Entech Instruments
Sorbent pen thermal conditioner Entech Instruments 3801-SPTC
Todd Hewitt (TH) media Sigma T1438-500G

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記事を引用
Phan, J., Kapcia III, J., Rodriguez, C. I., Vogel, V. L., Cardin, D. B., Dunham, S. J. B., Whiteson, K. Capturing Actively Produced Microbial Volatile Organic Compounds from Human-Associated Samples with Vacuum-Assisted Sorbent Extraction. J. Vis. Exp. (184), e62547, doi:10.3791/62547 (2022).

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