CN112941090A - 一种恶臭假单胞菌烯醇酶基因克隆方法与应用 - Google Patents
一种恶臭假单胞菌烯醇酶基因克隆方法与应用 Download PDFInfo
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Abstract
本发明公开一种恶臭假单胞菌烯醇酶基因克隆方法与应用。本发明针对PHA合酶在粗甘油中耐受力比较弱的问题,从恶臭假单胞菌烯醇酶基因组出发,加入引物PCR成功扩增得到1290bp的片段,通过酶切连接成功构建了载体pET28a‑Eno,经酶切和测序验证正确后转化进入大肠杆菌BL21中获得表达重组菌。对重组菌诱导表达的两个条件IPTG浓度和温度进行优化,成功使Eno包涵体表达大量可溶表达。这对于利用价格低廉的生物柴油副产物甘油合成PHA,解决生物柴油副产物过度积累带来的环境问题,降低PHA的生产成本具有重要意义。
Description
技术领域
本发明属于基因工程技术领域,涉及利用PCR技术克隆恶臭假单胞菌中烯醇酶基因,导入大肠杆菌中构成重组菌,对其诱导表达条件进行优化,并测定酶活力,进而解决粗甘油耐受力比较弱的问题。
背景技术
聚羟基脂肪酸酯(Polyhydroxyalkanonate,PHA)是很多微生物在碳源充足,氮源缺乏状态下产生的一类颗粒状、可作为生物体内碳源和能量储备物的高分子生物聚酯。由于PHA的优良性质,可以用在包装材料、医药行业和基因工程等。生物柴油的迅猛发展产生了大量的副产物,研究者在利用生物柴油副产物合成PHA时,发现一个问题,即微生物菌株对高浓度甘油耐受性较差,多数情况下,菌株在高浓度甘油条件下无法合成PHA,更不能直接利用生物柴油副产物合成PHA,当甘油的浓度的范围为1-5%时,为合成PHA的适宜浓度,这在一定程度上加大了PHA的生产成本。
恶臭假单胞菌(Pseudomonas putida KT2442)是一株来源于KT2440的线性聚酯类工业生产菌,通过发酵,细胞积累碳源和能量将糖类或者脂类转化为PHA。烯醇酶(Enolase,Eno)是一个抗逆性基因,带烯醇酶基因的菌株具有很强的抗逆性能力。研究表明,烯醇酶在厌氧、高盐、干旱、高温、低温等胁迫下会出现基因表达量的差异及酶活力的相应变化,从而为逆境下光合生物中被产生的大量自由基损伤的光合系统提供足够能量。
发明内容
本发明针对PHA在粗甘油中耐受力比较弱的问题,从恶臭假单胞菌中克隆抗逆性基因烯醇酶基因并将其导入筛选出来的耐受力比较好的菌株中构建重组菌,以提高重组菌对甘油的耐受力。这对于利用价格低廉的生物柴油副产物甘油合成PHA,解决生物柴油副产物过度积累带来的环境问题,降低PHA的生产成本具有重要意义。
本发明提供了一种利用PCR技术克隆烯醇酶基因导入大肠杆菌中构成重组菌,提高其对粗甘油的耐受力,进而降低PHA的生产成本。
本发明采用的技术方案是:一种恶臭假单胞菌烯醇酶基因克隆方法,包括如下步骤:
1)提取恶臭假单胞菌总DNA;
2)以提取的总DNA为模板,以上游引物P1和下游引物P2为特异性引物,通过PCR扩增获得目的片段;P1和P2的序列为:
P1:GATAAGCTTGTATGGCAAAAATCGTCG
P2:CATCTCGAGTTAGCCGCGAAACTC
3)将目的片段与表达载体pET28a经HindIII/XhoI双酶切,T4连接酶16℃过夜连接,获得重组质粒pET28a-eno;
4)将重组质粒pET28a-eno转化大肠杆菌感受态细胞中,获得重组菌;
5)将重组菌通过Kan抗性筛选阳性转化子;
6)挑取单菌落接种于含有Kan的培养液中培养过夜;按1-3%接种量转接于新鲜的LB培养基中,37℃培养至OD600为0.5,加入终浓度为0.2-1mM的IPTG,于20-30℃培养4h;8000rpm离心,收集菌体。
优选地,步骤2)中,PCR扩增体系是:ddH2O 32.5μl,10×PCR Buffer 5μl,Mg2+5μl,dNTP Mixture 4μl,模板DNA 1μl,上游引物P1(25μM)1μl,下游引物P2(25μM)1μl,pfu DNA聚合酶(5U/μl)0.5μl。
优选地,步骤2)中,PCR扩增条件是:95℃预变性8min;95℃变性45s,63℃退火30s,72℃延伸2min,35个循环;最后72℃延伸7min;4℃保存。
优选地,步骤4)中,加入IPTG至终浓度为1mM。
优选地,步骤4)中,于30℃培养4h。
通过本发明的方法获得的菌体在生物柴油副产物甘油合成PHA中的应用。
本发明的有益效果是:本发明提供了一种利用PCR技术扩增恶臭假单菌细胞中烯醇酶基因,转化进入大肠杆菌获得表达重组菌,当温度为20℃时,上清表达量较好,说明Eno包涵体表达大量可溶表达,提高了重组菌对粗甘油的耐受力,进而能利用价格低廉的生物柴油副产物甘油合成PHA。
附图说明
图1是PCR扩增烯醇酶基因电泳图;
其中,M:1kb DNA Marker;1,2:烯醇酶PCR扩增产物。
图2是pET28a-eno单双酶切电泳图;
其中,M:1kb DNA Marker;1:pET28a-Eno双酶切;2:pET28a-Eno单酶切;3:pET28a-Eno质粒。
图3是Eno诱导表达SDS-PAGE电泳图;
其中,M:蛋白分子量marker;1:未诱导全菌;2:诱导全菌;3:诱导表达破碎沉淀;4:诱导表达破碎上清。
图4是Eno不同浓度IPTG诱导表达SDS-PAGE电泳图;
其中,M:蛋白分子量marker;1,2:1.0mM IPTG诱导表达破碎上清;3:0.5mM IPTG诱导表达破碎上清;4:0.2mM IPTG诱导表达破碎上清;5,6:1.0mM IPTG诱导表达破碎沉淀;7:0.5mM IPTG诱导表达破碎沉淀;8:0.2mM IPTG诱导表达破碎沉淀。
图5是Eno不同温度IPTG诱导表达SDS-PAGE电泳图;
其中,M:蛋白分子量marker;1:20℃诱导表达破碎上清2:25℃诱导表达破碎上清;3:30℃诱导表达破碎上清;4:20℃诱导表达破碎沉淀;5:25℃诱导表达破碎沉淀;6:30℃诱导表达破碎沉淀。
图6是Eno诱导表达和纯化SDS-PAGE电泳图;
其中,M:蛋白分子量marker;1:未纯化Eno;2、3:纯化Eno。
具体实施方式
实施例1一种恶臭假单胞菌烯醇酶基因克隆方法
本实施例亲本采用恶臭假单胞菌(P.putida KT2442)
1、提取恶臭假单胞菌总DNA
从-80℃冰箱中,用接种环沾取恶臭假单胞菌菌液在培养基上划线过夜培养后,挑取平板上单菌落于10ml培养液中过夜培养后,与30%甘油按1:1体积混合于无菌的1.5ml冻存管中,分子克隆法提取恶臭假单胞菌总DNA基因组和质粒小量提取。
2、烯醇酶基因克隆
以提取的总DNA为模板,以上游引物P1和下游引物P2为特异性引物,通过PCR扩增获得目的片段;P1和P2的序列为:
P1:GATAAGCTTGTATGGCAAAAATCGTCG
P2:CATCTCGAGTTAGCCGCGAAACTC
PCR扩增条件是:95℃预变性8min;95℃变性45s,63℃退火30s,72℃延伸2min,35个循环;最后72℃延伸7min;4℃保存。
PCR扩增产物按照试剂盒(AxyPrep DNA Gel Extraction Kit)的说明步骤回收PCR产物。经电泳检测,如图1所示,PCR产物大小为1290bp,与预期结果基本一致。
3、重组质粒的构建
将目的片段与表达载体pET28a经HindIII/XhoI双酶切,在酶切反应体系中37℃酶切1h。在连接反应体系中16℃过夜,构建重组质粒pET28a-eno。
4、构建重组菌
将重组质粒pET28a-eno转化大肠杆菌感受态细胞BL21(DE3)中,获得重组菌。
将含有重组质粒pET28a-eno的重组菌菌液涂布于含有Kan抗性的LB平板上,挑取阳性克隆,培养后提取质粒经HindIII和XhoI双酶切筛选出阳性转化子。HindIII/XhoI双酶切验证连接结果并送测序公司测序。
pET28a-eno单双酶切电泳图如图2,由图2可见,挑取阳性克隆液体培养后为阳性转化子。
为保证不出现假阳性,同时取菌液送上海生物工程公司测序,测序结果表明,表达载体pET28a-eno构建成功,克隆的烯醇酶基因的DNA序列如SEQ ID NO.1所示。
5、目的蛋白诱导表达
将含有重组质粒pET28a-eno的重组菌菌液涂布于含有Kan抗性的LB平板上,筛选阳性克隆。挑取单菌落接种于含有Kan的培养液中培养过夜;按1-3%接种量转接于新鲜的LB培养基中,37℃培养至OD600约为0.5,加入终浓度为1mM的IPTG,于30℃培养4h;8000rpm收集菌体,水洗一次。
目的蛋白诱导表达后,每200ml初始培养物菌体用4ml结合缓冲液重悬,超声波破碎,400W,5s工作,5s间歇,重复20次;菌体破碎后经10000rpm离心20min去除细胞碎片,收集上清和沉淀,分别取40μl上清和沉淀加入10μl 5×SDS上样缓冲液混匀后SDS-PAGE分析。
如图3所示Eno表达时沉淀和上清均有表达,沉淀表达量远远大于上清表达量,说明Eno包涵体表达。
6、烯醇酶活性测定
6.1)Ni-NTA亲和层析柱的预处理:
①混匀固化Ni2+琼脂糖胶,取3ml加入层析柱,垂直固定,使胶自然沉降;
②加10倍体积的超纯水洗柱;
③加5倍体积的交换溶液以补充Ni2+;
④加5倍体积的平衡缓冲液,使柱子平衡至基线。
6.2)目的蛋白的纯化
层析柱平衡后,低速上样,并用20mM咪唑结合缓冲液平衡至基线,50mM、100mM、150mM、200mM咪唑洗脱缓冲液梯度洗脱,收集洗脱峰。
Ni2+琼脂糖柱子用平衡缓冲液平衡后,将上述纯化的蛋白过层析柱,收集洗脱峰进行SDS-PAGE,并进行Ni-NTA琼脂糖的再生。
取0.1ml经过Ni-NTA柱纯化的ENO加入1ml基质缓冲液,37℃水浴10min,加入2ml0.1M的HCl终止反应。同时设定对照管,对照管加0.1ml经过Ni-NTA柱纯化的ENO,以0.1M的HCl 2ml,然后加入1ml基质缓冲液。紫外分光光度计波长240nm,比色杯光径1cm,以对照管调零,读取测定管吸光度。按如下公式计算酶活性:
式中:A0为测定管吸光度;1300为磷酸烯醇式丙酮酸在240nm的摩尔吸光度。
可溶蛋白纯化后测定其吸光度值,根据公式计算得到烯醇酶的酶活力为510.39U/L。
实施例2 IPTG浓度条件优化
将含有重组质粒pET28a-eno的重组菌菌液涂布于含有Kan抗性的LB平板上,筛选阳性克隆。挑取单菌落接种于含有Kan的培养液中培养过夜;按1-3%接种量转接于新鲜的LB培养基中,37℃培养至OD600约为0.5,加入终浓度分别为1mM、0.5mM、0.2mM的IPTG,于30℃培养4h;8000rpm收集菌体,水洗一次。
目的蛋白诱导表达后,每200ml初始培养物菌体用4ml结合缓冲液重悬,超声波破碎,400W,5s工作,5s间歇,重复20次;菌体破碎后经10000rpm离心20min去除细胞碎片,收集上清和沉淀,分别取40μl上清和沉淀加入10μl 5×SDS上样缓冲液混匀后SDS-PAGE分析。
不同浓度的IPTG的电泳图如图4,表明IPTG浓度对烯醇酶的可溶表达影响小。
实施例3培养温度优化
将含有重组质粒pET28a-eno的重组菌菌液涂布于含有Kan抗性的LB平板上,筛选阳性克隆。挑取单菌落接种于含有Kan的培养液中培养过夜;按1-3%接种量转接于新鲜的LB培养基中,37℃培养至OD600约为0.5,加入终浓度为1mM的IPTG,于20℃、25℃、30℃培养4h;8000rpm收集菌体,水洗一次。
目的蛋白诱导表达后,每200ml初始培养物菌体用4ml结合缓冲液重悬,超声波破碎,400W,5s工作,5s间歇,重复20次;菌体破碎后经10000rpm离心20min去除细胞碎片,收集上清和沉淀,分别取40μl上清和沉淀加入10μl 5×SDS上样缓冲液混匀后SDS-PAGE分析。
由图5可见,温度对Eno的可溶表达影响较大,低温有利于Eno的可溶表达,当温度为20℃时,上清表达量较好。
<110> 辽宁大学
<120>一种恶臭假单胞菌烯醇酶基因克隆方法与应用
<160> 1
<170> SIPOSequenceListing 1.0
<210> 1
<211>1290
<212> DNA
<213>烯醇酶基因
<400> 1
ATGGCAAAAA TCGTCGACAT CAAAGGTCGT GAAGTTCTCG ACTCCCGTGG 50
CAACCCCACC GTCGAAGCCG ACGTGCTTCT CGATAACGGC ATCATCGGCA 100
GCGCCTGCGC GCCGTCCGGT GCTTCTACCG GTTCGCGCGA AGCGCTGGAA 150
CTGCGTGATG GCGACAAGAG CCGTTACCTG GGCAAAGGTG TACTCAAGGC 200
TGTAGCCAAC ATCAACGGCC CGATCCGTGA CCTGTTGCTG GGCAAGGACC 250
CGCTGGACCA GAAAGCCCTG GACCACGCGA TGATCAAGCT CGACGGCACT 300
GAAAACAAAG GCAGCCTGGG CGCCAACGCC ATCCTCGCCG TGTCCCTGGC 350
CGCTGCCAAG GCCGCCGCCC AGGACCAGGA CCTGCCGCTG TACGCCCACA 400
TCGCCAACCT GAACGGCACG CCGGGTGTGT ACTCGATGCC GGTGCCGATG 450
ATGAACATCA TCAACGGCGG TGAGCACGCT GATAACAACG TCGACATCCA 500
GGAATTCATG GTACAGCCGG TTGGCGCCAA GACCTTCTCC GAAGGCCTGC 550
GCATGGGCAC CGAGATTTTC CATCACCTCA AAGCTGTGTT GAAGGCCCGT 600
GGCCTGAGCA CCGCGGTGGG TGACGAGGGT GGTTTTGCCC CGAACCTGGC 650
GTCCAACGAA GATGCACTGA AAGTGATCTC CGAAGCCGTG GCCAACGCGG 700
GCTACAAGCT GGGCACCGAC GTGACCCTGG CTCTGGACTG CGCCGCCAGC 750
GAGTTCTACG AGGACGGTAA ATACAACCTG TCCGGCGAAG GCCACGTGTT 800
CACCTCCGAA GGTTTTGCTG ACTACCTCAA AGGCCTGACC GAGCGATACC 850
CGATCATCTC GATCGAAGAT GGCCTGGACG AGTCCGACTG GGCGGGCTGG 900
AAAGTCCTCA CCGACAAGAT CGGCGAGAAA ATCCAACTGG TCGGCGACGA 950
CCTGTTCGTG ACCAACACCA AGATCCTCAA AGAAGGCATC GACAAGCAGA 1000
TCGCCAACTC GATCCTGATC AAGTTCAACC AGATCGGCAC CCTGACCGAA 1050
ACCCTGGAAG CCATCCAGAT GGCCAAGGCC GCGGGCTACA CCGCCGTGAT 1100
CTCGCACCGC TCCGGCGAAA CCGAAGATTC GACCATTGCC GACCTGGCGG 1150
TGGGCACTTC GGCCGGCCAG ATCAAGACCG GCTCCCTGTG CCGTTCCGAC 1200
CGCGTGTCCA AGTACAACCA ATTGCTGCGT ATCGAAGAGC AACTGGCAGG 1250
TAAAGCCAAA TACAACGGTC GCAGCGAGTT TCGCGGCTAA 1290
Claims (6)
1.一种恶臭假单胞菌烯醇酶基因克隆方法,其特征在于,包括如下步骤:
1)提取恶臭假单胞菌总DNA;
2)以提取的总DNA为模板,以上游引物P1和下游引物P2为特异性引物,通过PCR扩增获得目的片段;P1和P2的序列为:
P1:GATAAGCTTGTATGGCAAAAATCGTCG
P2:CATCTCGAGTTAGCCGCGAAACTC
3)将目的片段与表达载体pET28a经HindIII/XhoI双酶切,T4连接酶16℃过夜连接,
获得重组质粒pET28a-eno;
4)将重组质粒pET28a-eno转化大肠杆菌感受态细胞中,获得重组菌;
5)将重组菌通过Kan抗性筛选阳性转化子;
6)挑取单菌落接种于含有Kan的培养液中培养过夜;按1-3%接种量转接于新鲜的LB培养基中,37℃培养至OD600为0.5,加入终浓度为0.2-1mM的IPTG,于20-30℃培养4h;8000rpm离心,收集菌体。
2.根据权利要求1所述的一种恶臭假单胞菌烯醇酶基因克隆方法,其特征在于,步骤2)中,PCR扩增体系是:ddH2O 32.5μl,10×PCR Buffer 5μl,Mg2+ 5μl,dNTP Mixture 4μl,模板DNA 1μl,上游引物P1(25μM)1μl,下游引物P2(25μM)1μl,pfu DNA聚合酶(5U/μl)0.5μl。
3.根据权利要求1所述的一种恶臭假单胞菌烯醇酶基因克隆方法,其特征在于,步骤2)中,PCR扩增条件是:95℃预变性8min;95℃变性45s,63℃退火30s,72℃延伸2min,35个循环;最后72℃延伸7min;4℃保存。
4.根据权利要求1所述的一种恶臭假单胞菌烯醇酶基因克隆方法,其特征在于,步骤4)中,加入IPTG至终浓度为1mM。
5.根据权利要求1所述的一种恶臭假单胞菌烯醇酶基因克隆方法,其特征在于,步骤4)中,于30℃培养4h。
6.按照权利要求1-5任意一项所述的方法获得的菌体在生物柴油副产物甘油合成PHA中的应用。
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