Cell-free supernatants of Bacillus inhibit the biofilms of Pseudomonas lundensis cultured with and without Acinetobacter johnsonii

[Objective] Pseudomonas as one of the dominant spoilage bacteria highly form biofilms in chilled meat products and processing environment when contaminating single or mixed with other species.This study aims to investigate the antibiofilm properties of the cell-free supernatants(CFSs) of three Bacillus species isolated from fermented food and rice seeds on Pseudomonas lundensis(PL) or and Acinetobacter johnsonii(AJ) as mono-or dual-species.[Methods] Biofilm biomass,extracellular polymeric substances(EPSs),and biofilm structure were measured by crystal violet staining,spectrophotometry,confocal laser scanning microscopy(CLSM),respectively,as well as transcription of biofilm-related genes determined by qPCR.[Results] The CFSs of Bacillus amyloliquefaciens ZG08,B.velezensis B5,and B.subtilis YB11 inhibited the biofilm formation of PL and AJ without affecting their growth.The treatment with 50% CFSs of ZG08 and B5 decreased the cell viability of two biofilms by 12.73%–21.04%,which was higher than that of YB11(0.15%–4.38%).The inhibition rates of 50% CFSs of the three strains were 59.75%–79.59% against the PL biofilm and 63.62%–78.57% against the biofilm of PL+AJ,in which the CFS of YB11 had weaker activity.The content of exopolysaccharides and exoprotein in the two biofilms treated with these CFSs were reduced by 53.77%–73.30% and 54.84%–62.38%,respectively.The treatment with the three CFSs also reduced the adhesive cells,loosened biofilm structures,and thinned their thickness by 57.63%–74.49% and 60.43%–64.64%,respectively.Moreover,the CFSs of ZG08 and B5 effectively eradicated by 41.77%–69.79% against the mature biofilms of PL and PL+AJ,compared to weak activity of YB11.In addition,the antibiofilm activities of the three CFSs were stable under four enzyme digestion and heating conditions.Compared with the control,the CFSs of ZG08 and B5 significantly down-regulated the expression of six biofilm-related genes,lapA,alg44,pelG,luxR,wspR,and rpoS.[Conclusion] The CFSs of ZG08 and B5 have strong antibiofilm activities against PL and AJ as mono-or dual-species.

离心弃沉淀处理对药品微生物限度检查结果影响的考察

目的:通过对供试液经500r/min离心5min后,考察细菌、霉菌和酵母菌在上清液及沉淀中的分配情况及对药品微生物限度检查结果的影响。方法:采用药用淀粉为供试品制备供试液,分别加入各验证菌,将其离心后对上清液和沉淀物分别进行细菌、霉菌和酵母菌的计数并与未经离心处理的供试液进行对比。结果:离心后分布在上清液中的细菌、霉菌和酵母菌数少于沉淀物中,细菌的回收率小于40%,霉菌和酵母菌回收率小于5%。结论:供试液经500r/min离心5min后取上清液弃沉淀的处理方式影响药物菌落计数的准确性,使结果明显偏低,是一种需改进的方法。

酵母菌代谢产物对植物乳杆菌AB-1生产苯乳酸的影响

以植物乳杆菌AB-1(Lactobacillus plantarum AB-1)为研究对象,探究不同培养基组成以及外源添加酵母菌无细胞发酵上清液(cell-free supernatant,CFS)对植物乳杆菌AB-1生产苯乳酸的影响。结果表明,将培养植物乳杆菌AB-1的MRS培养基中葡萄糖浓度由20.0 g/L提高至27.5 g/L、蛋白胨浓度由10.0 g/L提高至30.0 g/L时,苯乳酸产量从81.2 mg/L提高至103.8 mg/L,提高了27.8%(P<0.05)。在此基础上,外源添加15%经40 h发酵的酵母菌E1 CFS,可使苯乳酸产量达到130.2 mg/L,相较于优化MRS培养基和初始MRS培养基分别提高了25.4%和60.3%(P<0.05)。进一步研究表明,植物乳杆菌AB-1苯乳酸产量的提高可能与酵母菌CFS中苯丙氨酸(Phe)和α-酮戊二酸(α-KG)两种代谢产物有关。综上,该研究通过优化培养基及外源添加酵母菌CFS的方法,找到一种提高植物乳杆菌AB-1生产苯乳酸能力的培养方式。

Prenatal diagnosis of Down syndrome using cell-free fetal DNA in amniotic fluid by quantitative fluorescent polymersase chain reaction

Backgroud Amniotic fluid （AF） supernatant contains cell-free fetal DNA （cffDNA） fragments.This study attempted to take advantage of cffDNA as a new material for prenatal diagnosis,which could be combined with simple quantitative fluorescent polymerase chain reaction （QF-PCR） to provide an ancillary method for the prenatal diagnosis of trisomy 21 syndrome.Methods AF supernatant samples were obtained from 27 women carrying euploid fetuses and 28 women carrying aneuploid fetuses with known cytogenetic karyotypes.Peripheral blood samples of the parents were collected at the same time.Short tandem repeat （STR） fragments on chromosome 21 were amplified by QF-PCR.Fetal condition and the parental source of the extra chromosome could be determined by the STR peaks.Results The sensitivity of the assay for the aneuploid was 93％ （26/28; confidence interval,CI：77％-98％） and the specificity was 100％ （26/26; CI：88％-100％）.The determination rate of the origin of the extra chromosome was 69％.The sensitivity and the specificity of the assay in the euploid were 100％ （27/27）.Conclusions Trisomy 21 can be prenatally diagnosed by the QF-PCR method in AF supernatant.This karyotype analysis method greatly reduces the requirement for the specimen size.It will be a benefit for early amniocentesis and could avoid pregnancy complications.The method may become an ancillary method for prenatal diagnosis of trisomy 21.

酵母菌强化磷酸铵镁结晶体系处理富磷污泥上清液

利用一株除磷酵母菌在除磷过程中表面形成局部富磷区域的现象,将其引入到结晶除磷中,开发了酵母菌诱导强化磷酸铵镁(MAP)结晶协同除磷新体系。以A^(2)/O污泥浓缩池富磷上清液为处理对象,探究了pH、Mg/P、N/P、反应时间和搅拌强度对该体系除磷效能的影响,采用扫描电子显微镜能谱仪(SEM-EDS)、X射线衍射仪(XRD)分析结晶产物的形貌及晶型。结果表明,酵母菌诱导强化MAP结晶体系处理A^(2)/O污泥浓缩池富磷上清液的最优参数如下:pH=10.0、Mg/P=2.0、N/P=2.0、反应时间=30 min、搅拌强度=300 r/min,出水磷浓度可低至1.71 mg/L,除磷率为97.14%。结晶产物分析结果表明,酵母菌分泌的大量胞外聚合物(EPS)可以吸附废水中的PO_(4)^(3-)-P和Mg^(2+),在菌体周围形成富磷区域,进而以酵母菌为晶核形成MAP结晶产物,实现磷的去除与回收。