厦门市空气微生物的时空分布特征及其影响因素

Spatiotemporal distribution and influencing factors of airborne microbes in Xiamen of China

摘要:

【背景】城市环境中空气微生物的丰度、群落组成及其传输、扩散受区域环境和气象条件等多种因素的综合影响，并深刻影响着城市环境安全和居民健康。【目的】研究福建厦门不同季节、城市功能区和行政区空气细菌和真菌丰度和群落组成的时空分布特征，探讨影响空气微生物群落时空变化的主要影响因素，评估病原菌的潜在风险。【方法】采用大容量生物气溶胶采样器，于2021年夏季和2022年冬季在厦门市多个城市功能区采集了生物气溶胶样品，利用实时荧光定量PCR技术分析不同功能区和行政区空气细菌和真菌的绝对丰度，并探究其与环境因子的相关性；利用宏基因组测序技术分析厦门岛和同安区细菌群落组成，并开展潜在病原菌的风险评估。【结果】细菌绝对丰度在夏冬两季之间存在显著性差异(P<0.001)，冬季(平均2.17×10⁵ copies/m³)比夏季(平均3.18×10⁴ copies/m³)高1个数量级左右。公园中空气细菌绝对丰度最低，而在工业区最高。真菌绝对丰度在夏冬两季之间无显著性差异，夏季绝对丰度(平均4.24×10³ copies/m³)高于冬季(平均8.95×10² copies/m³)，最低绝对丰度出现在公园。夏季同安区空气细菌和真菌绝对丰度最高，并与其他3个行政区有显著性差异。在冬季，厦门岛细菌绝对丰度平均值最低，真菌最高，并且与其他3个行政区有显著性差异。采样点不同半径范围内“绿色空间”占比与细菌绝对丰度存在显著相关(P<0.01)。细菌绝对丰度与大气多个环境参数(NO₂、PM_2.5、SO₂、温度和相对湿度)有显著相关，而真菌仅与温度有显著正相关(P<0.01)。群落组成分析表明，厦门岛和同安区的优势菌群无明显的时空变异。冬季潜在病原菌的绝对丰度显著高于夏季(P<0.001)，工业区显著高于公园(P<0.05)。【结论】与全国其他城市相比，厦门市空气微生物的绝对丰度较低；空气细菌与真菌绝对丰度具有明显的空间差异；空气细菌绝对丰度具有明显的季节差异；厦门空气细菌和真菌的绝对丰度与环境因子息息相关，但其关键影响因子不尽相同。厦门岛和同安区的菌群组成具有较为稳定的时空分布特征，但潜在病原菌的风险冬季高于夏季，工业区高于公园。

Abstract:

[Background] The abundance of airborne microbes in urban environments, as well as their community composition, dispersion and transmission, are influenced by diverse factors such as regional environmental and meteorological conditions, which have profound impacts on the urban environmental security and the health of local residents. [Objective] To investigate the spatiotemporal distribution characteristics of the abundance and community composition of airborne bacteria and fungi in different urban functional zones and administrative districts of Xiamen in Fujian, explore the main influencing factors of the spatiotemporal distribution of airborne microbes, and evaluate the potential risks of pathogens. [Methods] This study employed a large-capacity sampler to collect bioaerosol samples from several urban functional zones of Xiamen in the summer of 2021 and the winter of 2022. Real-time quantitative PCR was employed to study the absolute abundance of airborne bacteria and fungi in different functional zones and administrative districts, and their correlations with environmental factors were analyzed; The composition of bacterial communities in Xiamen Island and Tongan district was analyzed by metagenome sequencing, and the risk of potential pathogens was evaluated. [Results] The bacterial absolute abundance was different between winter and summer (P<0.001), with the that in winter (average 2.17×10⁵ copies/m³) being approximately one order of magnitude higher than that in summer (average 3.18×10⁴ copies/m³). The bacterial absolute abundance was the lowest in the parks and the highest in the industrial areas. The fungal absolute abundance showed no significant difference between the winter and summer, with that in summer (average 4.24×10³ copies/m³) being higher than that in winter (average 8.95×10² copies/m³), and the lowest was observed in the parks. In summer, the absolute abundance of bacteria and fungi were the highest in Tongan district, which was significantly different from those in the other three administrative districts. In winter, Xiamen Island had the lowest average bacterial absolute abundance and the highest fungal absolute abundance, which showed significant differences from those in other three administrative districts of Xiamen. Within different radius ranges of sampling sites, the proportion of green space had a correlation (P<0.01) with bacterial absolute abundance. The bacterial absolute abundance showed significant correlations with environmental factors such as NO₂, PM_2.5, SO₂, temperature, and relative humidity. However, the fungal abundance only showed positive correlations with temperature (P<0.01). The community composition results revealed that the dominant bacteria in Xiamen Island and Tongan did not exist the significant spatiotemporal variation. The absolute abundance of potential pathogens was significantly higher in winter than in summer (P<0.001) and higher in industrial areas than in parks (P<0.05). [Conclusion] The absolute abundance of airborne microbes in Xiamen was at a low level compared with that in other cities in China. The absolute abundance of airborne bacteria and fungi showed significant spatial variations. The airborne bacterial absolute abundance exhibited significantly seasonal differences; The absolute abundance distribution of airborne bacteria and fungi in Xiamen showed closely relations with environmental factors, with the main influencing factors being different. The bacterial community composition showed relatively stable spatiotemporal distribution in Xiamen Island and Tongan, however, the risk of potential pathogens was higher in winter than in summer and higher in industrial areas than in parks.