Insect chitinases have been proposed as potential targets for pest control. In this work, a novel group IV chitinase gene, MdCht9, from Musca domestica was found to have multiple functions in the physiological activity, including chitin regulation, development and antifungal immunity. The MdCht9 gene was cloned and sequenced, its phylogeny was analysed and its expression was determined in normal and 20E treated larvae. Subsequently, RNA interference (RNAi)-mediated MdCht9 knockdown was performed, followed by biochemical assays, morphological observations and transcriptome analysis. Finally, the recombinant protein MdCht9 (rMdCht9) was purified and tested for anti-microbial activity and enzyme characteristics. The results showed that MdCht9 consists of three domains, highly expressed in a larval salivary gland. RNAi silencing of MdCht9 resulted in significant down-regulation of chitin content and expression of 15 chitin-binding protein (CBP) genes, implying a new insight that MdCht9 might regulate chitin content by influencing the expression of CBPs. In addition, more than half of the lethality and partial wing deformity appeared due to the dsMdCht9 treatment. In addition, the rMdCht9 exhibited anti-microbial activity towards Candida albicans (fungus) but not towards Escherichia coli (G-) or Staphylococcus aureus (G+). Our work expands on previous studies of chitinase while providing a potential target for pest management.

[目的]探明家蝇β-葡萄糖苷酶(β-glucosidase,BG)在家蝇体内的功能,为深入研究家蝇BG在木质纤维素降解中的作用奠定基础.[方法]针对家蝇BG基因的功能结构域设计3对特异性引物用于dsRNA的体外合成,通过显微注射的方法将dsRNA导入家蝇2龄幼虫,利用实时荧光定量PCR(RT-qPCR)检测抑制效率,分别以滤纸、水杨苷、微晶纤维素及羧甲基纤维素钠为底物检测BG基因的干扰对家蝇消化道粗酶液滤纸酶活性、BG、CBH(Cellobiohydrolase)及EG(Endoglucanase)酶活性的影响.[结果]在注射dsRNA后18 h家蝇幼虫消化道中BG基因的表达量下降62％且此时为最佳干扰时间点,在BG基因表达受到抑制后家蝇消化道的滤纸酶、BG酶活性显著降低,且时间变化趋势与上述干扰条件下BG基因表达量变化一致,均在干扰后18 h酶活性达最低,但CBH及EG酶活性较对照组无显著变化.[结论]RNA干扰技术能够有效抑制家蝇BG基因的表达,推测家蝇BG具有滤纸酶和BG酶活性.

Many insects are capable of developing enhanced resistance in response to repeated infection with the same pathogen, which is defined "immune priming". However, little is known in housefly, an ideal insect model for studying immunity. Here, Candida albicans (C. albicans) was used as the pathogen to explore whether housefly larvae are capable of eliciting immune priming. Firstly, we found that 2nd-instar larvae pre-exposure to heat-killed C. albicans could confer protection upon re-infection with C. albicans, as evidenced by the survival rate was higher in C. albicans primed larvae. Moreover, the hemocyte density was increased by priming, but phenoloxidase (PO) activity was not affected. For this reason, RNA sequencing (RNA-seq) was performed and found that 145 genes were differentially expressed after priming, in which 22 genes were related to immune response. Then, KEGG enrichment showed that Toll signaling pathway and Phagosome signaling pathway, as well as many other signaling pathways were enriched. Finally, qPCR was performed and found that the expression of 2 pattern recognition receptor (PRR) genes (PGRP-SD-like precursor and lectin subunit alpha-like) and 6 immune effector genes (phormicin, cecropin-A2-like, defensin-1, attacin-A-like, sarcotoxin-1C and lysozyme 1-like) in C. albicans primed larvae was significantly up-regulated after challenge. Taken together, our findings suggested that housefly larvae are capable of eliciting immune priming against C. albicans, and cellular immunity as well as the gene expression, especially genes involved in Toll signaling pathway were induced by immune priming with C. albicans.

Chitinases are hydrolytic enzymes that play important roles in chitin degradation during the insect development process, and thus are considered as the potential targets for pest management. Here, we identified and characterized the group VII chitinase gene from health pest Musca domestica (MdCht2). We found that MdCht2 was 1932 bp in length with an open reading frame of 1530 bp, which encodes a polypeptide of 509 amino acid residues. Phylogenetic analysis showed that MdCht2 gene was homologs with other closed insects, and belong to the group VII chitinases. Moreover, Real-time PCR analysis indicated that MdCht2 mRNA was highly expressed in pupa stage, as well as in integument and trachea. However, RNAi-mediated knockdown of MdCht2 resulted in high mortality rates and abnormal eclosion. Therefore, we hypothesized that MdCht2 was a crucial gene required for housefly development, which was supported by the transcription level of MdCht2 could be induced by 20hydroxyecdysone (20E), and the dsMdCht2 could resulted in decrease of the chitinase activity and increase of the chitin content. Taken together, our findings suggested that MdCht2 regulated the chitin content via chitinases, thereby leading to abnormal development. Our results provide a potential target for M. domestica management.

Abstract The 14-3-3 gene plays important role in many biological processes, including cell survival, apoptosis, and signal transduction. However, function of the 14-3-3 homologous gene in Musca domestica remains unclear. Here, we identified and characterized the 14-3-3ζ of M. domestica. We found that Md14-3-3ζ gene was highly homologous with other close insects. The qRT–PCR analysis revealed that the Md14-3-3ζ was highly expressed in adults, and was expressed predominantly in hemocytes and fat body. Meanwhile, the expression of Md14-3-3ζ was up-regulated after injecting Escherichia coli and Staphylococcus aureus. Moreover, the recombinant protein rMd14-3-3ζ strongly inhibits the growth of E. coli and S. aureus. Notably, the rMd14-3-3ζ inhibits E. coli and S. aureus by permeating the cell membrane. Taken together, our findings suggested that Md14-3-3ζ is involved in the immune response against bacteria through damaging the cell membrane.

目的 了解不同生物被膜形成能力的临床分离耐碳青霉烯类鲍曼不动杆菌菌株(CRAB)基因表达的差异.方法 选取8株临床分离CRAB,将生物被膜形成能力强的菌株4、55、78、117号作为强生物被膜(BF)组,将生物被膜形成能力弱的菌株13、177、191、196号作为弱生物被膜(WBF)组,培养两组菌株形成生物被膜,分别提取RNA进行文库构建和转录组测序(RNA-Seq),以鲍曼不动杆菌AB030(NZ_CP009257.1)的基因组作为参考基因组对测序数据进行分析,鉴定差异表达基因(DEGs),并进行基因本体(GO)功能注释和京都基因与基因组百科全书(KEGG)通路富集分析,选取8个DEGs利用实时荧光定量PCR(qRT-PCR)验证转录组测序结果.结果 RNA样品完整无污染,测序数据错误率为0.03％;BF组与WBF组相比,鉴定到171个DEGs,其中106条基因为上调表达,65条基因为下调表达;这些基因主要涉及DNA结合、膜蛋白、菌毛调控、ATP的合成和分解等;GO分析显示较多基因被注释到生物过程部分,KEGG分析显示DEGs富集到多种物质代谢途径;选取的8个DEGs利用qRT-PCR进行验证,结果与转录组测序结果趋势一致.结论 不同生物被膜形成能力的临床CRAB的基因表达存在差异,多基因和多条信号通路影响生物被膜的形成.

几丁质酶是昆虫几丁质降解过程中的重要酶类,在昆虫整个生长发育过程中发挥着重要作用.为筛选及挖掘与防治有害医学昆虫相关的分子靶标,根据家蝇几丁质酶2(Musca domestica chitinase 2,MdCht2)基因序列设计并合成双链RNA(double-stranded RNA,dsRNA),采用微量注射法向家蝇2龄幼虫导入dsRNA,对对照组及干扰组的样本进行转录组测序,筛选差异表达基因,进行GO(gene ontology)功能注释和KEGG(kyoto encyclopedia of genes and genomes)通路富集分析.结果显示,注射dsRNA 24 h后,幼虫MdCht2 mRNA的表达显著下降,提示导入的dsRNA干扰了MdCht2的表达.经转录组测序,与对照组相比,显著差异基因共213条,其中78条基因为上调表达,135条基因为下调表达.随机选取8条显著差异基因通过实时荧光定量PCR(qRT-PCR)进行验证,该结果与转录组结果趋势一致.根据功能注释发现这些差异基因与生长发育、脂类代谢、免疫调控等途径相关.本研究通过RNA干扰和转录组测序技术处理家蝇获得大量差异基因,结果可为后续几丁质酶相关基因的挖掘和鉴定及功能研究提供一定的数据基础.

为探明家蝇重组Serpin15蛋白的体外活性和酶稳定性,本文对家蝇Serpin15基因进行了生物信息学分析和克隆表达,并对纯化后的家蝇重组Serpin15蛋白进行了酶特性的研究.结果显示:家蝇Serpin15基因ORF框全长为1353 bp,编码450个氨基酸,理论分子量为51076.63 Da,有信号肽和一个标志抑制活性的功能结构域RCL反应环;成功构建原核表达载体pET-28a(+)-Serpin15,经诱导表达和纯化获得家蝇重组Serpin15蛋白;重组蛋白酶特性研究发现,家蝇重组Serpin15蛋白对胰蛋白酶有极显著的抑制作用,此外,将重组Serpin15蛋白经20～60℃热处理15 min,或经pH 6～10过夜处理,或经50℃和pH 8处理后室温存放15～90 min,重组蛋白的胰蛋白酶抑制活性均仍大于70％.研究结果为家蝇Serpin15蛋白的免疫功能研究奠定了重要实验基础,也为有害昆虫杀虫剂的研发提供思路.

目的 了解临床分离的耐碳青霉烯类鲍曼不动杆菌(CRAB)生物被膜态和游离态的转录组差异,探究生物被膜形成的机制.方法 从住院病人痰液或血液样本分离CRAB 4、55、78及117菌株,挑取单菌落分别培养生物被膜态菌(A组)和游离态菌(B组),采用Trizol法提取2组细菌核糖核酸(RNA)样本进行转录组测序;使用DESeq软件进行差异表达基因(DEGs)分析,通过GOSeq R软件进行基因本体(GO)富集分析,通过KO-BAS软件进行京都基因与基因组百科全书(KEGG)通路富集分析;选择8个DEGs,利用实时荧光定量PCR(qRT-PCR)验证转录组测序分析结果.结果 RNA样品完整无污染满足测序要求,测序数据错误率不超过0.03％;A与B组相比鉴定到407个差异基因,其中212条基因为上调表达,195条基因为下调表达,涉及铁的摄取和转运、菌毛合成的调控、生化代谢酶类及转录调节因子等;GO分析显示,GO条目主要富集于分子功能类别和生物过程类别;KEGG分析显示,DEGs富集到硫代谢、ATP结合盒(ABC)转运系统、万古霉素耐药、群体感应及阳离子抗菌肽耐药等多条通路;选取的8个差异基因通过qRT-PCR进行验证,结果与转录组结果趋势一致.结论 临床分离的CRAB菌株,其生物被膜态和游离态存在基因表达差异,生物被膜的形成涉及多基因和多信号通路参与.

为探索天敌昆虫与云南木蠹象之间的信息联系机制,研究天敌寄生蜂定向到该虫的种间化学信号,为筛选对天敌寄生蜂具有生物活性的引诱剂,实现对该虫的生态控制提供理论参考.采用固相微萃取和气质联用(SPME-GC-MS)技术,对云南木蠹象幼虫危害的云南松带虫树皮和带虫木质部挥发性成分进行了研究.云南松带虫树皮挥发性化合物主要包括7类37种,分别是萜烯类21种、醇类7种、酮类4种、醚类2种、烷烃类1种、酯类1种和烯烃1种;云南松带虫木质部挥发性化合物主要包括6类40种,分别是萜烯类24种、醇类7种、酮类5种、烷烃类2种、酯类1种和氧化物1种.

载体植物系统作为一种新型的生物防治手段,具有良好的防治效果和应用价值.蚕豆蚜Aphis fabae偏好豆科植物,对茶树安全,且作为猎物可满足南方小花蝽Orius strigicollis生长和繁殖的需要.因此本研究以蚕豆蚜作为替代猎物、蚕豆Vicia faba作为载体植物及南方小花蝽作为天敌昆虫构建"南方小花蝽-蚕豆-蚕豆蚜"载体植物系统来防治茶叶害虫.为探究该载体系统是否可有效控制茶叶害虫,本研究事先在室内比较了该载体植物系统与直接释放南方小花蝽对茶蚜Toxoptera aurnantii的防治效果;之后在田间调查中发现茶树上主要有茶蚜、茶棍蓟马Dendrothrips minowai及小贯小绿叶蝉Empoasca onukii共3种害虫混合发生,且它们均可被南方小花蝽捕食,因此在田间试验中本研究同时评价了载体植物系统及直接释放南方小花蝽对这3种害虫的防治效果.结果显示:在室内试验中,载体植物系统与直接释放南方小花蝽相比,在前3次调查中茶蚜种群数量显著降低,且虫口减退率及防治效果均显著高于直接释放南方小花蝽,其中载体植物系统对茶蚜的控制效果最高可达92.16％,而直接释放南方小花蝽对茶蚜的防治效果仅为72.25％,表明该载体植物系统有应用于田间防治茶叶害虫的潜力.在田间试验中,载体植物的布局(条状、块状及点状)对载体植物系统的防治效果无显著影响;载体植物系统与直接释放南方小花蝽均对小贯小绿叶蝉有显著的防治效果,且最高防效均在90％左右,但对茶蚜及茶棍蓟马则无明显的控制作用,表明载体植物系统与直接释放南方小花蝽均可用于茶叶害虫的防治,但在应用时需考虑到多种害虫同时发生对防治效果的影响.

The transposon vector containing enhanced green fluorescent protein (EGFP) was injected into early housefly (Musca domestica L.) eggs by microinjection method to realize stable gene expression in vivo for verification, and to study housefly gene function. A borosilicate glass micro injection needle suitable for microinjection of housefly eggs was made, the softening treatment conditions of housefly egg shells were explored, and a microinjection technology platform suitable for housefly was constructed with a high-precision microsyringe Nanoject Ⅲ as the main body. The recombinant plasmid PiggyBac-[3×P3]-EGFP containing the eye-specific 3×P3 promoter and EGFP and the stable genetic expression helper plasmid pHA3pig helper were microinjected into the treated housefly eggs. After emergence, the eye luminescence was observed, and the expression and transcription level of EGFP were detected. The results showed that the normal hatching rate of housefly eggs was 55% when rinsed in bleaching water for 35 s. The hardness of the egg shell treated for 35 s was suitable for injection and the injection needle was not easy to break. About 3% of the emerged housefly eyes had green fluorescence. Through further molecular detection, EGFP specific fragments with a size of 750 bp were amplified from DNA and RNA of housefly. Through the technical platform, the stable expression of reporter genes in housefly can be conveniently and effectively realized, and a bioreactor with housefly as the main body can be established, which provides certain reference value for subsequent research on housefly gene function.

The stick tea thrip Dendrothrips minowai (Priesner) (Thysanoptera: Thripidae) is a destructive pest in tea plantations in south and southwest China. To control this pest, a non-crop banker plant system was developed using a polyphagous predator Orius strigicollis (Poppius) (Heteroptera: Anthocoridae) with the black bean aphid Aphis fabae (Scopoli) (Hemiptera: Aphididae) as an alternative prey and the faba bean Vicia faba as the banker plant to support the predator in targeting the pest. The fitness of A. fabae on tea plants and faba bean was evaluated to determine its host specificity. Moreover, the control efficacy of the banker plant system on D. minowai on tea plants was tested in the laboratory and compared with that of direct release of O. strigicollis. The experiments showed that faba bean was an excellent non-crop host for A. fabae because, while the aphid population increased quickly on faba bean, it could only survive for up to 9 days on tea plants. Compared with direct release of O. strigicollis, lower densities of pest were observed when introducing the banker plant system. Our results indicate that this banker plant system has the potential to be implemented in the field to improve the control of the pest thrips.

小花蝽是农业生产上一类极具利用和开发前景的捕食天敌昆虫,人工饲养扩繁是小花蝽广泛应用的前提,然而在大规模饲养中产卵基质、饲料和饲养条件等制约了人工饲养扩繁.为小花蝽大规模生产及田间大面积推广应用提供参考,从小花蝽人工饲养(产卵基质、饲料、饲养条件、饲养工具及储藏条件)、捕食能力和应用技术等方面综述小花蝽的研究进展,.

南方小花蝽Orius strigicollis作为一种广食性捕食性天敌昆虫,可高效控制蓟马、蚜虫及螨类等多种害虫,极具生防潜能.但目前国内南方小花蝽商业化进程相对滞后,其中未找到适合的饲料来源是主要的限制因素之一.本研究以新鲜麦蛾Sitotroga cerealella卵和紫外线处理的麦蛾卵作为饲养南方小花蝽的替代猎物,以南方小花蝽的天然猎物西花蓟马Frankliniella occidentalis为对照,通过比较其发育历期、存活率及寿命等生物学指标,组建生命表来评价麦蛾卵对南方小花蝽的饲喂效果.结果发现:以新鲜麦蛾卵、紫外处理麦蛾卵和西花蓟马饲喂的南方小花蝽若虫发育历期均无显著性差异,但取食新鲜麦蛾卵的南方小花蝽若虫存活率(60.5％)高于其他两种猎物;同时,饲喂新鲜麦蛾卵的南方小花蝽雌虫寿命(37.3 d)和雄成虫寿命(23.0 d)以及产卵量(74.0粒)均最高,其次是紫外处理麦蛾卵,而西花蓟马最低;饲喂新鲜麦蛾卵的南方小花蝽存活率、净增殖率(47.91)、内禀增长率(0.10)、周限增长率(1.11)和世代平均周期(36.5 d)均大于饲喂紫外处理麦蛾卵和饲喂西花蓟马,且种群加倍时间也以饲喂新鲜麦蛾卵的南方小花蝽最短(6.57 d).本研究结果表明麦蛾卵可作为南方小花蝽饲养的替代猎物,且以新鲜麦蛾卵为最佳.

储蓄植物系统作为一种开放式的天敌饲养系统,越来越多地应用到温室及田间的害虫防治.南方小花蝽 Orius similis Zheng可捕食蓟马、蚜虫等多种害虫,是农业上一类极具应用价值的捕食性天敌.为提高南方小花蝽的控害效果,建立南方小花蝽储蓄植物系统是一种极为有效的方法.为了筛选适用于南方小花蝽保育和增殖的储蓄植物,进而构建南方小花蝽储蓄植物系统,本研究选择了月季Rosa chinensis、长寿花Narcissus jonquilla、辣椒Capsicum annuum、黄瓜Cucumis sativus和蚕豆Vicia faba作为候选的储蓄植物,通过六臂嗅觉仪分析了南方小花蝽对5种植物花朵的气味选择性,同时分析了南方小花蝽在5种植物上的繁殖系数、发育历期、存活率等生物学参数.结果表明43.33％的南方小花蝽雌虫偏好辣椒花朵气味,其次为蚕豆(26.67％);南方小花蝽卵的孵化率在辣椒上最高达到95.59％,其次为蚕豆为80.74％;同时,南方小花蝽卵在蚕豆上的发育历期显著低于另外4种植物,仅有4.92 d.综上所述,本研究初步认为辣椒和蚕豆比较适合用来构建南方小花蝽储蓄植物系统.

本文旨在探明家蝇Musca domestic幼虫对高粱秸秆和小麦秸秆营养成分利用和木质纤维素的降解情况,以及不同配比秸秆饲料对家蝇生物学指标的影响,为今后产业化利用家蝇来生物降解秸秆类有机废弃物奠定理论基础.本研究采用70％高粱秸秆粉、70％麦秸秆粉和纯麦麸作为饲料,每种饲料各设置对照组、发酵组和家蝇幼虫取食组3种处理,检测并分析3种饲料各处理组中一般营养成分和木质纤维素的含量及变化;同时采用7种配比饲料喂养家蝇,观察各组家蝇不同发育阶段的体长、体重、存活率和发育历期等.结果表明:(1)3种饲料的各处理组中,一般营养成分和木质纤维素的含量均呈现:对照组>发酵组>家蝇取食组的趋势,此外除高粱秸秆组粗蛋白外,其余各组成份均差异显著(P<0.05);(2)小麦秸秆的木质纤维素含量>高粱秸秆>麦麸,且各组间均差异显著(P<0.05);(3)在相同秸秆配比条件下,高粱秸秆饲喂的家蝇其各虫态体长、体重、总存活率和发育历期均要优于麦秸秆喂养,且总存活率和发育历期与麦麸喂养相比差异不显著(P>0.05);(4)纯高粱秸秆喂养下家蝇仍能保持正常的生长发育,而在90％小麦秸秆喂养下,家蝇则无法存活.综上所述,家蝇适合作为生物转化器用于秸秆、尤其是高粱秸秆的降解,且降解效果优于单纯的微生物发酵降解,研究结果为今后规模化利用家蝇降解秸秆类有机废弃物提供了理论依据和科学基础.

为Rhodosporidiobolus odoratus菌株中病毒的鉴定提供参考,从Rhodosporidiobolus odora-tus菌株GZ2017中,分离真菌病毒Rhodosporidiobolus odoratus Totivirus 1(RoTV1);获取并解析真菌病毒RoTV1的全长基因组序列;明确真菌病毒RoTV1的病毒学分类学地位.采用随机引物法扩增病毒的全长序列;使用接头引物扩增法获取病毒末端序列;获取的病毒片段通过DNAMAN软件进行拼接;序列同源性搜索使用NCBI网站的在线BLAST程序;使用MEGA7.0软件进行系统进化树的构建.结果表明:成功分离新型真菌病毒RoTV1,其携带3条病毒条带,分别为dsRNA1、dsRNA2和dsRNA3.获得RoTV1的全长基因组序列,其中,dsRNA1序列分析显示具有2个不连续的开放阅读框(Open Reading Frame,ORF),即ORF1和ORF2.ORF1和ORF2分别跟全病毒科(Totiviridae)全病毒属(Totivirus)真菌病毒编码的外壳蛋白(Coat Protein,CP)和RNA依赖的RNA聚合酶(RNA dependent RNA polymerase,RdRp)具有较高的相似性.ORF1和ORF2之间间隔92个碱基.ORF2有可能通过1个由移码序列(GGAUUUU)启动的-1核糖体移码机制跟ORF1融合成1个大的融合蛋白.对dsRNA2和dsRNA3序列进行分析,未发现编码有意义的大ORF,无已知的蛋白质与dsRNA2和dsRNA3具有序列相似性.此外,dsRNA1、dsRNA2、dsR-NA3在菌株GZ2017中非常稳定和相互依赖,推测dsRNA2和dsRNA3可能是dsRNA1的卫星RNA(SatRNA).另外,基于RoTV1的RdRp和CP序列进行的系统发育分析表明,RoTV1属于Totiviridae科Totivirus属的新成员.

为评价南方小花蝽Orius similis对非洲菊上西花蓟马的控制效果,本研究在非洲菊上以2头/m2密度释放南方小花蝽,以西花蓟马的虫口减退率及南方小花蝽对西花蓟马校正防效作为指标评价了其控害效果.结果显示:在释放南方小花蝽前期,南方小花蝽对非洲菊上西花蓟马的控制效果不明显,但随着释放时间延长,控制效果显著提高,释放南方小花蝽21 d后的控制效果高达90.25％,而喷施化学农药的控制效果为?40.93％,释放南方小花蝽的控制效果远高于喷施化学农药处理,表明南方小花蝽对西花蓟马具有更高效持久的控制潜力.

结合不同抗菌肽的优点与抗菌肽Cec4杂合,以提高其抗菌能力.通过杂合肽进行序列比对、3级结构预测、相关抗菌效果等参数分析,设计出可能具有更强抗菌能力的杂合肽6条.进而采用微量稀释法,检测杂合肽对大肠杆菌、白色念珠菌、金黄色葡萄球菌、及各类鲍曼不动杆菌的最小抑菌浓度(minimum inhibitory concentration,MIC).杂合肽Cec4-1-1、Cec4-4-2与母肽Cec4对革兰氏阴性菌(大肠杆菌)的抑菌效果相当,Cec4-2-1对大肠杆菌的MIC值为2μg/mL,其抑菌效果优于母肽Cec4.杂合肽和母肽Cec4对革兰氏阳性菌(金黄色葡萄球菌)、真菌(白色念珠菌)均无抑菌效果.杂合肽Cec4-1-1、Cec4-2-2、Cec4-4-2与母肽Cec4对各类鲍曼不动杆菌的抑菌效果相当,Cec4-2-1对标准鲍曼不动杆菌的MIC值为0.5 μg/mL,其抑菌效果优于母肽Cec4.综上,杂合肽Cec4-1-1、Cec4-2-1、Cec4-2-2、Cec4-4-2对各类鲍曼不动杆菌均有较强抑菌活性且对人红细胞无溶血反应.