王浩然 張連越 劉沛余
摘要:為探究濟南冬季泉水水系中細菌的生態(tài)分布、未培養(yǎng)趨磁細菌及其磁小體形態(tài)的多樣性,選擇濟南市泉水源頭、護城河及泉水匯集的大明湖等8處不同位點,于2018年1月13日收集水底表層泥樣,富集環(huán)境中趨磁細菌,提取樣品總DNA,進行16S rDNA高通量測序及生物信息學分析,并利用透射電子顯微鏡觀察和統(tǒng)計趨磁細菌及磁小體的形態(tài),揭示濟南泉水水系中趨磁細菌的分布特征。結果表明,濟南冬季泉水水系中趨磁細菌分布明顯不均,泉水源頭處未檢測到趨磁細菌;黑虎泉下游護城河中發(fā)現了少量單鏈趨磁球菌,基因序列表明為新種,暫定為η-變形菌綱(Candidatus Etaproteobacteria)的一個菌株;眾泉匯集的大明湖中趨磁細菌種類最多,且細菌和磁小體形態(tài)多樣性復雜。微生物多樣性分析發(fā)現,冬季泉水水系中細菌種類主要是變形菌門(Proteobacteria)、藍細菌門(Cyanobacteria)和綠彎菌門(Chloroflexi),三者總豐度均占細菌總量的65%以上,具有磁細菌生長所需的群落環(huán)境。本研究可為深入研究未培養(yǎng)趨磁細菌的全基因組及可培養(yǎng)條件等提供素材與線索。
關鍵詞:濟南泉水;冬季;趨磁細菌;磁小體;暫定η-變形菌綱;16S rRNA;微生物多樣性
中圖分類號:S273:Q938.8文獻標識號:A文章編號:1001-4942(2020)04-0079-07
Abstract In order to explore the ecological distribution of bacteria, the diversity of uncultured magnetotactic bacteria (MTB) and their magnetosome morphology in Jinan spring water system in winter, the water sludge samples were collected from 8 sites in the fountainhead, mead stream Hucheng River and downstream Daming Lake on January 13, 2018. The MTB cells were gathered from the sludge samples and used to extract the genome DNA for high-throughput sequencing and bioinformatics analysis. The morphology of MTB and magnetosome were observed by transmission electron microscope, and the distribution features of MTB in Jinan spring water in winter were revaled. The results showed that the distribution of MTB in Jinan spring water system was obviously uneven. No MTB was detected at the fountainheads. A small amount of single-stranded magnetococci was found in the downstream of Heihu Spring, which is a strain of Candidatus Etaproteobacteria. Daming Lake had the most diverse types of magnetotactic bacteria, and the morphology of bacteria and magnetosomes was diverse. Microbial diversity analysis showed that the types of bacteria in the spring water system in winter were mainly Proteobacteria,Cyanobacteria and Chloroflexi, whose abundance was more than 65%. The results in this article would provide materials and clues for the further researches of the whole genome and cultured conditions.
Keywords Jinan spring water; Magnetotactic bacteria; Magnetosome; Candidatus Etaproteobacteria; 16S rDNA; Microbial diversity
趨磁細菌是一類可沿地球磁場運動的微生物總稱,廣泛存在于海洋和湖泊中。其獨特之處在于胞內能夠合成由生物膜包被的納米級磁性顆?!判◇w(magnetosome),目前發(fā)現的磁小體主要成分為磁鐵礦或膠黃鐵礦[1]。相對于人工合成的磁性顆粒,磁小體具有眾多優(yōu)點,如化學組分純度高、質地均一、熱損耗高等,具有廣闊的應用前景。然而,趨磁細菌生長條件苛刻,實驗室條件下僅有少量趨磁細菌(如AMB-1)能被純培養(yǎng)[2],這給其深入研究帶來較大困難。
快速發(fā)展的宏基因組技術為未培養(yǎng)微生物的研究開拓了全新的方法,人們可通過對環(huán)境中微生物遺傳物質的分析探究趨磁細菌種群的種類、分布以及功能基因簇的起源與系統(tǒng)發(fā)育等。由于環(huán)境條件可能作為重要的進化壓力,在趨磁細菌長期演化過程中扮演重要角色,因此認識不同季節(jié)不同天然條件下趨磁細菌的分布就引起人們廣泛的興趣。前人研究揭示,在河流、湖泊、海洋等常見水體及以鹽堿湖和熱泉為代表的極端環(huán)境中趨磁細菌都具有復雜的生物多樣性[1,3-6],且種類的分布與環(huán)境因子體現出明顯相關性[7, 8]。目前還未見有關趨磁細菌在冬季泉水這種寡營養(yǎng)水體環(huán)境中的生物多樣性研究。本試驗即以冬季寡營養(yǎng)的濟南天然泉水水系為研究對象,分析趨磁細菌的分布以及細菌和磁小體的形態(tài)多樣性,揭示不同區(qū)域泉水的微生物多樣性,為進一步研究趨磁細菌與環(huán)境微生物群落之間的關系奠定基礎。