蒙小俊,李海波,盛宇星,曹宏斌*(1.安康學(xué)院旅游與資源環(huán)境學(xué)院,陜西 安康 75000；.中國(guó)科學(xué)院過(guò)程工程研究所綠色過(guò)程與工程重點(diǎn)實(shí)驗(yàn)室,北京 100190)

焦化廢水活性污泥PAH雙加氧酶基因多樣性分析

蒙小俊1,2,李海波2,盛宇星2,曹宏斌2*(1.安康學(xué)院旅游與資源環(huán)境學(xué)院,陜西 安康 725000；2.中國(guó)科學(xué)院過(guò)程工程研究所綠色過(guò)程與工程重點(diǎn)實(shí)驗(yàn)室,北京 100190)

為分析焦化廢水活性污泥中降解PAH雙加氧酶的多樣性,利用16Sr DNA-PCR-DGGE方法,以實(shí)際焦化廢水好氧單元活性污泥總DNA為模板,通過(guò)引物對(duì)污泥中的雙加氧酶基因進(jìn)行了克隆表達(dá)和多樣性分析.結(jié)果表明,以活性污泥總 DNA為模板,利用引物RHD-GN-610F和RHD-GN-916R擴(kuò)增后有明顯的產(chǎn)物,產(chǎn)物大小約為300bp;DGGE指紋圖譜顯示PCR產(chǎn)物有8條分離條帶,豐度分別為2.99%、8.16%、20.75%、28.50%、8.62%、7.26%、10.62%和13.10%;條帶經(jīng)切膠回收PCR擴(kuò)增后出現(xiàn)明顯的擴(kuò)增產(chǎn)物,TA克隆后成功測(cè)試出4條序列,長(zhǎng)度分別為305bp,298bp,334bp和294bp,表明焦化廢水活性污泥中存在不同降解PAH的RHD酶.這些結(jié)果為焦化廢水中PAHs的風(fēng)險(xiǎn)評(píng)估及其潛在生物降解提供理論基礎(chǔ).

焦化廢水；PAHs；活性污泥；雙加氧酶基因

PAHs是一類由稠合芳環(huán),不含取代基或雜原子組成的有毒有害化合物,這類物質(zhì)常以混合的形式存在,廣泛分布于不同性質(zhì)的水環(huán)境介質(zhì)中,如生活廢水和工業(yè)廢水中.在廢水的處理過(guò)程中PAHs會(huì)大量積存于初沉池污泥、活性污泥、消化污泥、脫水污泥和外排污泥中,對(duì)微生物活性有負(fù)效應(yīng),因致突、致畸和致癌使該類物質(zhì)成為最危險(xiǎn)的有機(jī)污染物之一.因與固體顆粒有很強(qiáng)的親和性,在廢水處理過(guò)程中 PAHs很容易被吸附在固體顆粒表面,吸附作用是 PAHs在廢水處理過(guò)程中去除的主要途徑[1-3].焦化廠是環(huán)境中PAHs的主要來(lái)源之一,焦化排放的PAHs占我國(guó)多環(huán)芳烴年排放總量的17.9%,尤其如萘、菲、芘、苯并[a]芘是焦化廢水中PAHs的典型代表[4-6].焦化廢水生化處理過(guò)程中PAHs的遷移轉(zhuǎn)化主要是依賴生物反應(yīng)器中生物污泥-微生物群落的吸附降解耦合作用來(lái)去除,在生物反應(yīng)器中多環(huán)芳烴遷移轉(zhuǎn)化的可能途徑主要是生物污泥的吸附,其次是緩慢的生物降解,多環(huán)芳烴的水溶解度隨著分子量的增大而降低,水相遷移能力也隨之變差,多環(huán)芳烴會(huì)更容易被懸浮物和沉積物吸附[7-10].焦化廢水中PAHs的最終去除依靠微生物的降解作用,已從焦化廢水活性污泥、土壤或者其他場(chǎng)所鑒定出多株具有降解多環(huán)芳烴能力的菌株,如芘降解菌Pseudomonas sp.[11], Burkholderia sp.[11]和Diaphorobacter sp.[12]等,萘降解菌如 Streptomyces sp.[13]和 Geobacillus sp.[14]等,菲降解菌如Pseudomonas sp.[15]和Sphingomonas sp.[16]等.

PAHs的生物降解需要多種酶系的參與,酶系的生成和不同活性都是由相關(guān)基因進(jìn)行編碼控制,其中重要的關(guān)鍵啟動(dòng)酶為環(huán)羥基雙加氧酶(RHD),它決定和控制后續(xù)的生物降解步驟和速率.RHD由β和α終端雙加氧酶,鐵氧化還原蛋白和鐵氧化還原蛋白酶組成,在 PAH環(huán)裂解過(guò)程中另外還需雌二醇雙加氧酶的參與,在不同的染色體或質(zhì)粒位點(diǎn)上,不同的 PAH降解菌具有不同的 RHD編碼基因[17-18].已從紅杉沉淀物中發(fā)現(xiàn)nidA和ndo (nahAc and phnAc)終端雙加氧酶基因[19-20],利用實(shí)時(shí)定量 PCR從土壤和沉積物樣品中成功克隆和鑒定出降解 PAHs的環(huán)羥化雙加氧酶基因RHD[21-22].降解PAHs的雙加氧酶基因具有相似性和多樣性,如高效降解芘的放線菌 Mycobacterium sp.雙加氧酶大亞基和小亞基的基因片段與已知降解芘的分枝桿菌的雙加氧酶基因具有高度同源性[23],而降解蒽嗜鹽菌AD-3 的雙加氧酶基因與 Marinobacter sp.NCE312菌株萘雙加氧酶大亞基的部分氨基酸序列同源性相似[24],嗜鹽菌群萘雙加氧酶(ndo)基因有6種基因型[25].實(shí)際焦化廢水處理工藝好氧單元多以活性污泥法為主,然而好氧單元活性污泥PAHs雙加氧酶基因多樣性未見(jiàn)報(bào)道.對(duì)編碼降解PAH啟動(dòng)基因RHD進(jìn)行克隆表達(dá)和多樣性分析有利于降解PAHs功能微生物的監(jiān)測(cè),風(fēng)險(xiǎn)評(píng)估及其PAHs的潛在生物降解.本研究利用16Sr DNA- DGGE技術(shù)對(duì)采自實(shí)際焦化廢水處理廠好氧單元的活性污泥分析其RHD基因的多樣性.

1 材料與方法

1.1 實(shí)驗(yàn)試劑

D5625-01E.Z.N.A.Soil DNA Kit(OMEGA)、Q10212Qubit2.0DNA 檢測(cè)試 劑 盒(Life)、Ep0406Taq DNA Polymerase(Thermo) 、SK8192SanPrep柱式DNA膠回收試劑盒(上海生工).

1.2 實(shí)驗(yàn)主要儀器

Pico-2臺(tái)式離心機(jī)(Thermo Fisher)、GL-88B漩渦混合器(海門(mén)市其林貝爾儀器制造有限公司)、 TND03-H-H干式恒溫器(深圳拓能達(dá)科技有限公司)、DYY-6C電泳儀電源(北京市六一儀器廠)、DYCZ-21電泳槽(北京市六一儀器廠)、GelDoc-It310凝膠成像系統(tǒng)(美國(guó) UVP)、Qubit?2.0Q32866熒光計(jì)(Invitrogen)、T100TMThermal Cyeler PCR儀(BIO-RAD)、DGGE儀(Bio-Rad).

1.3 采樣

活性污泥采自遼寧某焦化廠好氧單元,該焦化廢水生物處理系統(tǒng)采用A-A-O工藝,表1為主要水質(zhì)指標(biāo)和好氧單元工藝參數(shù),SRT為15～18d,活性污泥中16種EPA優(yōu)控PAHs單體濃度為18.95～68.50μg/g.

表1 焦化廢水主要水質(zhì)指標(biāo)和好氧單元工藝參數(shù)Table 1 Major indices of coking wastewater and operational parameters of aerobic basin

1.4 樣品總DNA提取和PCR擴(kuò)增

活性污泥基因組 DNA 通過(guò) E.Z.N.A. Soil DNA Kit 提取,Qubit2.0檢測(cè)DNA濃度,瓊脂糖凝膠檢測(cè)DNA完整性.

所用引物為PAH-RHD,如表2所示[21-22].反應(yīng)體系50μL:10×Buffer(含2.0mmol/L MgCl2)5μL, dNTP(10mmol/L)1μL,GC(10μmol/L)1μL,NS1(10 μmol/L)1μL,Taq酶(5U/μL)0.25μL,母板 DNA 2μL,ddH2O補(bǔ)至50μL.PCR擴(kuò)增程序:94℃ 5min預(yù)變性;94℃變性 30s,54℃退火 45s,72℃延伸1min,35個(gè)循環(huán);延伸7min,4℃保存.取PCR產(chǎn)物各2μL,1.5%瓊脂糖,1×TAE緩沖液,120V穩(wěn)壓電泳 15min,利用凝膠成像系統(tǒng)拍攝電泳圖譜查看PCR的擴(kuò)增效果.

表2 PCR擴(kuò)增引物Table 2 PCR amplification primers

1.5 變性梯度凝膠電泳DGGE和條帶回收

利用D-Code突變檢測(cè)系統(tǒng)對(duì)上述PCR產(chǎn)物(取PCR產(chǎn)物400ng)進(jìn)行DGGE分析,8%的聚丙烯酰胺凝膠濃度,變性劑濃度梯度 15%～40%,電壓條件為70V,60℃恒溫,1×TAE中電泳13h.電泳結(jié)束后,利用超純水將膠沖洗干凈放入含 TE的染液中染色 30min,然后置于凝膠成像系統(tǒng)上拍攝圖譜.待凝膠成像系統(tǒng)拍攝電泳圖譜結(jié)束后,用潔凈的手術(shù)刀片將預(yù)先挑選的代表性目標(biāo)DGGE條帶完整地切下裝入1.5mL離心管中,按上海生工公司試劑盒方法進(jìn)行回收,備用.

1.6 PCR擴(kuò)增、產(chǎn)物回收和目標(biāo)片段測(cè)序

PCR反應(yīng)體系與程序同上.PCR產(chǎn)物按上海生工測(cè)序公司 SK8131試劑盒方法切膠回收.依次經(jīng)過(guò)連接、感受態(tài)細(xì)胞制備、連接產(chǎn)物轉(zhuǎn)化、藍(lán)白斑篩選和質(zhì)粒提取過(guò)程后對(duì)目標(biāo)片段進(jìn)行測(cè)序,測(cè)序由上海生工完成.

2 結(jié)果與討論

2.1 PCR擴(kuò)增產(chǎn)物和DGGE指紋圖譜分析

提取活性污泥樣品總DNA后,利用表2中的引物以總DNA為模板進(jìn)行PCR擴(kuò)增,發(fā)現(xiàn)引物RHD-GN-610F和RHD-GN-916R有明顯的擴(kuò)增產(chǎn)物,如圖1所示,產(chǎn)物大小為300bp,這與相關(guān)研究報(bào)道結(jié)果一致[21,24],說(shuō)明 A-A-O處理工藝好氧單元活性污泥中存在降解PAHs的RHD基因酶.

圖1 PCR擴(kuò)增產(chǎn)物Fig.1 PCR amplification product

圖2 RHD基因DGGE 指紋圖譜分析Fig.2 DGGE analysis of RHD genes

對(duì)樣品PCR產(chǎn)物進(jìn)行DGGE分析,發(fā)現(xiàn)有明顯的分離條帶(圖2),分別編號(hào)1、2、3、4、5、6、7、8(圖2),說(shuō)明焦化廢水活性污泥中RHD基因存在多樣性.RHD基因酶由β和α終端雙加氧酶,鐵氧化還原蛋白和鐵氧化還原蛋白酶組成,在不同的染色體或質(zhì)粒位點(diǎn)上,不同的PAH降解菌具有不同的 RHD編碼基因[17-18].焦化廢水活性污泥是一個(gè)復(fù)雜的微生物群落,存在不同的 PAHs降解菌株,如 Burkholderia sp.和 Pseudomonas sp.、Comamonas sp.和Diaphorobacter sp.等[26-28]. 8條條帶的亮度如圖2所示,亮度的大小可反映該條帶的豐富度,表3所示8條帶所占的豐度分別為2.99、8.16、20.75、28.50、8.62、7.26、10.62和13.10%,主要條帶為3和4號(hào)條帶,推測(cè)3和4號(hào)條帶的RHD基因酶是焦化廢水中降解PAHs的主要酶.用潔凈的手術(shù)刀片將1～8號(hào)目標(biāo)DGGE條帶完整的切下利用引物 RHD-GN-610F和RHD-GN-916R PCR擴(kuò)增后進(jìn)行電泳檢測(cè).

表3 RHD基因的多樣性和豐度Table 3 Diversities and richness of RHD genes

2.2 DGGE條帶PCR產(chǎn)物電泳分析

圖3 DGGE條帶PCR產(chǎn)物電泳圖Fig.3 Electrophoresis of DGGE band PCR products

如圖3所示,對(duì)DGGE指紋圖譜中的8條條帶進(jìn)行回收經(jīng)PCR擴(kuò)增后發(fā)現(xiàn)有明顯的擴(kuò)增產(chǎn)物,進(jìn)一步證實(shí)了活性污泥中存在不同的 RHD基因酶,不同的PAH降解菌具有不同的RHD編碼基因[18],說(shuō)明焦化廢水活性污泥中存在不同的PAHs降解菌株,萘、菲、芘的代謝過(guò)程分別說(shuō)明

[18],RHD 加氧酶是 PAHs好氧代謝過(guò)程中最重要的關(guān)鍵酶和啟動(dòng)酶,決定和控制后續(xù)的生物代謝過(guò)程.

2.3 DGGE條帶PCR產(chǎn)物序列分析

為了分析 DGGE條帶 PCR產(chǎn)物的序列,回收產(chǎn)物依次經(jīng)過(guò)連接、感受態(tài)細(xì)胞制備、連接產(chǎn)物轉(zhuǎn)化、藍(lán)白斑篩選和質(zhì)粒提取過(guò)程后對(duì)目標(biāo)片段進(jìn)行測(cè)序,成功測(cè)試出條帶編號(hào)分別為4、5、6和7的序列,序列長(zhǎng)度分別為305bp、298bp、334bp、294bp,結(jié)果如下所示:

條帶4:305bp

GAGATGCATACCACGTTGGTTGGACGC ACGCATCGTCTTTGCGCTCGGGGCAGTCGA TATTTACTCCTCTTGCGGGCAACGCGATGCT TCCACCCGAAGGCGCGGGCTTGCAAATGAC CAGCAAGTATGGCAGTGGAATGGGCGTATT GTGGGACGCCTACTCCGGTGTCCACAGCGC TGATCTGGTTCCCGAAATGATGGCATTCGGC GGCGCAAAACAGGAAAAGCTCGCCAAAGA AATCGGCGATGTCCGGGCGCGGATTTACCG CAGCCATCTGAACAGCACTATCTTCCCGAA CAACAGC

條帶5:298bp

GAGATGCATACCACGTTGGTTGGACGC ACGCATCGTCTTTGCGCACAGGGCAGTCGA TATTTACCCCTCTTGCGGGCAACGCTATGCC TCCACCCGAAGGCGCGGGCTTACAAGTGA CCAGCAAGTATGGCAGTGGAATGGGCGTAT TGTGGGACGCCTACTCCGGTGTCCACAGCG CAGACCTGGTTCCCGAAATGATGGCATTCG GCGGCGCAAAACAGGAAAAGCTCGCCAAG AAATCGGCGATGTCCGGGCGCGGATTTACC GCAGCCATCGTCGACCTGCAGGCATGCAAG CT

條帶6:334bp

GAGATGCATACCACGTTGGTTGGACGC ACGCATCGTCTTTGCGCTCAGGGCAGTCGA TATTTACCCCTCTTGCGGGCAACGCTATGCC TCCACCCGAAGGCGCGGGCTTACAAGTGA CCAGCAAGTATGGCAGTGGAATGGGCGTAT TGTGGGACGCCTACTCCGGTGTCCACAGCG CTGATCTGGTTGCCGAACTGATGGCATTCG GCGCCGCAAGACAGGAAAAACTCGCCAAG GAAATCGGCGTTGTCCGGGCACAGATTTAC CGCAGCCATCTAAACAGCACTATCTTCCCG AACAACAGCTAACCGCACTATCTTCCCGAA CAACAGCT

條帶7:294bp

AGATGCATACCACGTTGGTTGGACGCA CGCATCGTCTTTGCGCACAGGGCAGTCGAT ATTTACTCCTCTTGCGGGCAACGCTACGCTT CCACCCGAAGGCGCGGGCTTGCAAATGAC CAGCAAGTATGGCAGTGGAATGGGCGTATT GTGGGACGCATACCACGTAGGTTGGACGCA CGCATCGTCTTTGCGCTCAGGGCAGTCGAT ATTTACTCCTCTTGCGGGCAACGCGATGCTT CCACCCGAAGGCGCGGGCTTGCAAATGAC CAGCAAGTATGGCAGTGGAATGGGCGT

利用BLAST在NCBI數(shù)據(jù)庫(kù)(http://blast.stva.ncbi.nlm.nih.gov/Blast.cgi)中進(jìn)行同源性檢索BLAST比對(duì)分析顯示:條帶4,條帶5,條帶6和條帶 7分別與 PAH雙加氧酶基因(Accession AM743143.1), (Accession JX297666.1), (Accession AM743159.1),和(Accession AM743143.1)相似,相似度分別為98%,97%,96%和98%,說(shuō)明克隆表達(dá)成功測(cè)序的4條的序列基因均為PAH雙加氧酶基因.

3 結(jié)論

3.1 提取焦化廢水活性污泥樣品總 DNA,利用引物以總 DNA為模板 PCR擴(kuò)增,發(fā)現(xiàn)引物RHD-GN-610F和RHD-GN-916R擴(kuò)增后有明顯產(chǎn)物,對(duì)PCR擴(kuò)增產(chǎn)物進(jìn)行DGGE分析,發(fā)現(xiàn)有8條條帶,豐度分別為2.99%、8.16%、20.75%、28.50%、8.62%、7.26%、10.62%和13.10%.

3.2 8條條帶經(jīng)切膠回收PCR擴(kuò)增后有明顯產(chǎn)物,進(jìn)一步證實(shí)了活性污泥中存在不同的 RHD基因酶.TA克隆后.成功測(cè)試出4條序列.長(zhǎng)度分別為305bp、298bp、334bp和294bp.

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Diversity of PAH dioxygenase genes of activated sludge from coking wastewater.

MENG Xiao-jun1,2, LI Hai-bo2, SHENG Yu-xing2, CAO Hong-bin2*
(1.School of Tourism and Environment, Ankang University, Ankang 725000, China；2.Key Laboratory of Green Process and Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China). China Environmental Science, 2017,37(1)：367～372

In order to analyze the biodiversity of PAH dioxygenase in activated sludge from a full-scale coking wastewater, primers were used for dioxygenase gene cloning expression and diversity analysis by 16Sr DNA-PCR-DGGE method using total DNA of aerobic activated sludge as the template. The results showed that significant amplification product was found using primers RHD-GN-610F and RHD-GN-916R, and the product size was 300bp. PCR product was conducted by DGGE analysis and eight separate bands were found, the abundance was 2.99%, 8.16%, 20.75%, 28.50%, 8.62%, 7.26%, 10.62% and 13.10%, respectively. Obvious amplification products further appeared after strips by gel extraction and PCR amplification, and 4sequences were tested successfully by TA cloning, the length of the sequences was 305bp, 298bp, 334bp and 294bp, respectively, indicating the presence of different PAH RHD enzymes in coking activated sludge. These results provide a theoretical basis for the risk assessment and potential biodegradation of PAHs.

coking wastewater；PAHs；activated sludge；dioxygenase gene

X703

A

1000-6923(2017)01-0367-06

蒙小俊(1981-),男,陜西漢中人,博士,主要從事生物法處理工業(yè)廢水研究.發(fā)表論文16篇.

2016-05-10

安康學(xué)院高層次人才科研專項(xiàng)經(jīng)費(fèi)(2016AYQDZR09);國(guó)家自然科學(xué)基金項(xiàng)目(31370281);化學(xué)工業(yè)廢水處理污泥污染特征與污染風(fēng)險(xiǎn)控制研究(201509053)

* 責(zé)任作者, 研究員, hbcao@home.ipe.ac.cn