光滩生物膜的鉴定和组成分析

Identification and composition analysis of biofilms on mudflat

【目的】建立光滩生物膜的判定方法。【方法】采集光滩生物膜及其附近表层沉积物,利用18SrRNA基因测序研究生物膜及其附近表层沉积物的优势藻种及其丰度差异;使用叶绿素a (chlorophyll a, Chl-a)检测和流式细胞检测,对生物膜及其附近表层沉积物的叶绿素a浓度和含有Chl-a的细胞量进行研究。【结果】光滩生物膜主要含有硅藻(Diatomea)、甲藻(Dinoflagellata)、色藻(Ochrophyta)、绿藻(Chlorophyta)、隐藻(Cryptophyceae)和轮藻(Phragmoplastophyta),不同季节和地理位置的生物膜优势藻种的相对丰度存在显著变化。光滩生物膜和附近表层沉积物之间的Chl-a浓度存在显著差异,生物膜中含有Chl-a的细胞量显著高于附近表层沉积物。通过藻类相对丰度、Chl-a浓度和含有Chl-a的细胞量构建了光滩生物膜的判定方法,即藻类相对丰度>40%,Chl-a浓度>500 mg/m^(3)且含有Chl-a的细胞量>500 cell/μL时,判定为有生物膜,反之判定为无生物膜,含有Chl-a的细胞量>1500cell/μL时,判定生物膜为生长旺盛期,含有Chl-a的细胞量介于500-1 500 cell/μL时,判定生物膜为定殖期或衰退期。【结论】本研究探讨了光滩生物膜及其附近表层沉积物的优势藻种类型及其丰度差异,评估了生物膜及其附近表层沉积物中Chl-a浓度和含有Chl-a的细胞量,并基于上述认识制定了光滩生物膜有无的判定方法,拓宽了对光滩生物膜的认知,为进一步开展生物膜固碳潜力相关研究提供了理论依据。

[Objective]To establish a methodology assessing the existence and active state of biofilms on mudflat.[Methods]We sampled the biofilms on mudflat and the surface sediments in the nearby regions,and compared the dominant algal species and their abundance between the biofilms and their nearby regions by 18S rRNA gene sequencing.Furthermore,we employed chlorophyll a(Chl-a)assay and flow cytometry to compare the concentration of Chl-a and the amount of Chl-a-containing cells between the biofilms and their nearby regions.[Results]The mudflat biofilms mainly harbored Diatomea,Dinoflagellata,Ochrophyta,Chlorophyta,Cryptophyceae,and Phragmoplastophyta,the relative abundance of which,however,varied significantly in different seasons or geographic locations.There was a significant difference in the concentration of Chl-a between biofilms and their nearby regions.The amount of Chl-a-containing cells in biofilms was significantly higher than that in the nearby regions.A method for assessing biofilms on mudflat was established based on the relative abundance of algae,the concentration of Chl-a,and the amount of Chl-a-containing cells.In brief,a sample is classified as a biofilm in the case of the relative abundance of algae higher than 40%,the Chl-a concentration higher than 500 mg/m^(3),and the amount of Chl-a-containing cells more than 500 cells/μL.Otherwise,the sample is classified as inexistence of biofilm.Additionally,the amount of Chl-a-containing cells more than 1500 cells/μL indicates that the biofilm is in the vigorous growth phase,and that between 500 cells/μL and 1500 cells/μL suggests that the biofilm is in the colonization or recession phase.[Conclusion]We compared the dominant algal species and their relative abundance,the concentration of Chl-a,and the amount of Chl-a-containing cells between biofilms on mudflat and their nearby regions,and established a methodology assessing the existence and active state of biofilms on mudflat based on the above indicators.The findings enriched the knowledge of biofilms on mudflat and provided a theoretical basis for understanding the microbial carbon sequestration capacity of biofilms on mudflat.