Tryptophan-like and humic-like fluorophores are extracellular in groundwater: implications as real-time faecal indicators.
Tryptophan-like and humic-like fluorophores are extracellular in groundwater: implications as real-time faecal indicators.
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DOI：
10.1038/s41598-020-72258-2
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发表时间：
2020-09-21
影响因子：
4.6
通讯作者：
Taylor RG
中科院分区：
文献类型：
--
作者：
Sorensen JPR;Carr AF;Nayebare J;Diongue DML;Pouye A;Roffo R;Gwengweya G;Ward JST;Kanoti J;Okotto-Okotto J;van der Marel L;Ciric L;Faye SC;Gaye CB;Goodall T;Kulabako R;Lapworth DJ;MacDonald AM;Monjerezi M;Olago D;Owor M;Read DS;Taylor RG
荧光天然有机物在类荧光（TLF）和类腐殖酸荧光（HLF）峰与地下水中的粪便指示细菌的存在和计数。然而，我们假设，在这些波长下发出荧光的主要是细胞外物质，而不是细菌细胞。我们量化了肯尼亚、马拉维、塞内加尔和乌干达城市人口密度范围内140个地下水源中的总（未过滤）和细胞外（过滤< 0.22 µm）TLF和HLF。当过滤后荧光发生变化时，它们与潜在的控制变量相关。在整个数据集中观察到滤过后TLF（ΔTLF）显著降低，尽管大部分信号保留，因此认为是细胞外信号（中位数96.9%）。ΔTLF仅在TLF最大的城市化程度更高的研究地区具有显著性。在塞内加尔达喀尔以下，ΔTLF与细菌总数显著相关（ρs 0.51）。在所有数据中，过滤后HLF没有显著变化，表明这些荧光团是细胞外的。我们的研究结果表明，TLF和HLF是更多的移动的比粪便指示细菌和更大的病原体在地下水中，主要是细胞外的荧光团是不太容易应变。因此，TLF/HLF比粪便指示细菌更能预防地下水饮用水中的微生物风险。
Fluorescent natural organic matter at tryptophan-like (TLF) and humic-like fluorescence (HLF) peaks is associated with the presence and enumeration of faecal indicator bacteria in groundwater. We hypothesise, however, that it is predominantly extracellular material that fluoresces at these wavelengths, not bacterial cells. We quantified total (unfiltered) and extracellular (filtered at < 0.22 µm) TLF and HLF in 140 groundwater sources across a range of urban population densities in Kenya, Malawi, Senegal, and Uganda. Where changes in fluorescence occurred following filtration they were correlated with potential controlling variables. A significant reduction in TLF following filtration (ΔTLF) was observed across the entire dataset, although the majority of the signal remained and thus considered extracellular (median 96.9%). ΔTLF was only significant in more urbanised study areas where TLF was greatest. Beneath Dakar, Senegal, ΔTLF was significantly correlated to total bacterial cells (ρs 0.51). No significant change in HLF following filtration across all data indicates these fluorophores are extracellular. Our results suggest that TLF and HLF are more mobile than faecal indicator bacteria and larger pathogens in groundwater, as the predominantly extracellular fluorophores are less prone to straining. Consequently, TLF/HLF are more precautionary indicators of microbial risks than faecal indicator bacteria in groundwater-derived drinking water.
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