提高鱼精蛋白对革兰氏阴性菌抗菌活性的研究

测定了鱼精蛋白对常见食品污染菌的抑制效果和最低抑菌浓度 (MIC) ;通过鱼精蛋白与甘氨酸、醋酸钠复合 ,或与冷冻并用等方法 ,提高了鱼精蛋白对革兰氏阴性菌的抗菌活性     

鱼精蛋白抗菌机制的研究

鱼精蛋白是一种存在于各类动物精巢组织中的多聚阳离子肽,其抗菌性很早就被所知,然而它的抗菌机理却一直未能得到很清楚的了解。现存在的机理有2种:一种认为鱼精蛋白与细菌细胞壁结合,通过破坏细胞壁的形成来达到抑菌效果;另一种认为鱼精蛋白破坏了细胞能量的转换、营养物质的吸收功能,细胞质膜是鱼精蛋白攻击的对象。事实上,作者认为,鱼精蛋白的抗菌效果可能是通过以上2种方式共同作用的结果,因而它的抗菌机理也可能是这两种机理的叠加,这还需进一步的研究证明。     

TLC-生物自显影-MTT法检测滇重楼内生真菌中抗菌活性成分

本文采用TLC-生物自显影-MTT法检测了3株滇重楼内生真菌即芬芳镰刀菌、季氏毕赤氏酵母和烟曲霉正丁醇提取物对大肠杆菌、枯草芽孢杆菌、白色念珠菌和稻瘟病菌的抗菌活性成分,以芬芳镰刀菌和季氏毕赤氏酵母菌液提取物中含有的抗菌活性成分为多.同时与打孔药剂扩散法的检测结果进行了比较,为进一步快速分离内生真菌中抗菌活性成分提供了依据.     

鱼精蛋白抑菌机理及在食品防腐中的应用

鱼精蛋白是一类天然的阳离子抗菌肽,具有广谱抑菌活性。鱼精蛋白主要是通过破坏细菌的细胞壁、细胞膜及改变细胞的渗透性等途径抑制甚至杀死细菌细胞。在鱼精蛋白抑制细菌的同时,细菌也产生多种机制对抗鱼精蛋白。温度、pH、阳离子和EDTA等多种理化因子影响鱼精蛋白对细菌的抑制效果。由于鱼精蛋白在抑菌防腐方面的众多优势,目前已成为非常有发展前景的食品防腐剂。     

以甘草为原料的食品天然防腐剂的研制

采用不同的溶剂和提取条件,提取甘草中的抗菌有效成分,然后通过抑菌试验筛选出抗菌力最强的制剂,通过测定该制剂对常见食品污染菌的最小抑菌浓度(MIC),证实该制剂对多种常见的食品污染菌均有较强的抑制作用,保存试验证实本制剂能有效地延长食品的保质期。     

酒花浸膏及其异构化衍生物抗食品腐败菌的初步研究

以啤酒花及其异构化衍生物为原料,从中初筛出两种最有效抗菌成分β-酸和六氢β-酸,并测定其对几种常见食品腐败菌的抑制作用和最低抑菌浓度,结果表明β-酸(20×10-6)、六氢β-酸(8×10-6)对肉制品中的主要污染菌--李斯特菌有抑制作用,对荧光假单孢菌、普通变形杆菌也有较明显的抑制效果.     

海洋真菌抗病原菌生物活性物质的研究

对分离自大连海域的海洋生物共附生真菌进行了抗菌活性的初筛与复筛,发现有6株具有抗表皮葡萄球菌和铜绿假单胞菌的活性,发现培养基成分及培养方式对活性菌株抗菌物质的产生有显著影响。菌株11-N2抗菌活性最强,其发酵液抗表皮葡萄球菌的效价相当于为氨苄青霉素11.4 U/mL,抗铜绿假单胞菌的效价相当于氨苄青霉素6.0 U/mL。通过硅胶柱层析对该菌株提取物的抗菌活性成分进行了初步追踪,发现二氯甲烷∶甲醇=15∶1洗脱组分具有最强活性,薄层层析显示该组分主要成分在254 nm紫外光下具有强吸收,薄层显色反应提示其主要成分可能为含胺基的甾体或三萜类、有机胺类、吲哚衍生物类化合物。     

六种中草药提取物对两株口腔致病菌的体外抗菌活性

采用二倍稀释法,以中草药提取物中的总黄酮、总有机酸和总皂苷等主要活性成分为定量标准,测定艾叶、侧柏叶、金银花、蒲黄、三七、仙鹤草提取物对变异链球菌和牙龈卟啉单胞菌的最低抑菌浓度(MIC)与最低杀菌浓度(MBC);并用大孔吸附树脂进行富集和除杂,探讨其可能的抗菌成分。结果发现金银花提取物对两株菌具有较好的抗菌效果,且总黄酮和有机酸是其主要的抗菌成分;三七提取物纯化后总皂苷浓度增大了1.7倍,对牙龈卟啉单胞菌由无抑菌变成抑菌作用;其它4种草药提取物纯化前后抗菌效果无明显改变。因此金银花总黄酮和总有机酸可认为是其主要的抗菌成分;三七总皂苷很有可能是抑制牙龈卟啉单胞菌生长的物质。     

三株亚肉座菌乙酸乙酯提取物生物活性及GC-MS分析

采用乙酸乙酯提取3株亚肉座菌菌丝体,测试虫生真菌乙酸乙酯提取物（EAE）的抗肿瘤、抗菌和抗氧化活性,并借助GC-MS方法分析各提取物中的化学成分。结果发现2株亚肉座菌的菌丝体EAE对HepG2细胞的抑制活性较强,IC₅₀均小于9μmol/L;抗菌结果表明2株真菌的提取物具有抑制细菌生长的作用;1株供试菌的EAE表现出较强的DPPH自由基清除活性（清除率可达85%）。GC-MS分析表明从亚肉座菌JXJG201717、JXJG201720和ARSEF7697的EAE中分别鉴定出21、35和39种成分,主要成分为酯类、醇类和酸类;盘状亚肉座菌JXJG201720与ARSEF7697有相同化合物13个,与暹罗亚肉座菌JXJG201717存在7个相同化合物。本研究表明虫生亚肉座菌具有产生丰富活性成分的能力,彰显出多种利用价值。     

2010 年上海市食源性沙门菌菌型分布和药敏分析 以及快速检测方法的建立

目的:通过对2010年上海市市售食品中食源性沙门菌污染状况、菌型分布及药敏试验进行分析,初步确定该地区食源性沙门菌的菌型分布及耐药性,为防治因沙门菌感染引起的食源性疾病提供科学依据,并摸索建立了针对沙门菌的快速检测方法。方法:对农贸市场和超市的5类840份市售食品进行沙门菌分离鉴定及耐药性分析,并根据沙门菌的侵袭蛋白A(invA)基因序列设计保守引物,特异性快速检测沙门菌。结果:本次市售食品沙门菌阳性率检出率为4.29%,共36株沙门菌,生禽畜肉所占比例高达91%。主要血型为鼠伤寒沙门菌,德尔卑沙门菌和都柏林沙门菌。36株沙门菌药敏分析显示:所有菌株对头孢类等抗生素敏感较高,但对氨苄西林、麦迪霉素、环丙沙辛、呋喃妥因等存在普遍较多耐药菌株,并在此基础上通过PCR法成功地特异性检测出沙门菌。结论:上海市市售食品沙门菌污染以生禽畜肉为主,对抗菌药物的耐药性较高。目前治疗市售食品中食源性沙门菌引起的食源性疾病应首选头孢内等抗生素。另外PCR快速检测方法也操作简单,特异性强,灵敏度高,对食品中沙门菌污染能起到快速检测和监控。     

鲤鱼鱼精蛋白的提取及抑菌活性研究

以鲤鱼的成熟精巢为原料,经0.15 mol/L NaCl溶液浸提,硫酸解离,并分别经乙醇、丙酮分离提取鱼精蛋白。测定了鱼精蛋白对细菌和真菌的最低抑制浓度以及在不同pH条件下的抑菌特性,试验结果表明鱼精蛋白具有较好的热稳定性,与EDTA复合使用可以增强抑菌效果,在酱油中可以代替苯甲酸的防腐作用。     

Solubility and antimicrobial efficacy of protamine on Listeria monocytogenes and Escherichia coli as influenced by pH

The antimicrobial efficacy of protamine on Listeria monocytogenes and Escherichia coli was evaluated at concentrations from 50 to 10 000 microgram ml-1 and pH levels from 5.5 to 8.0. The minimum inhibitory concentrations decreased with increasing pH. Protamine inhibited E. coli at all pH values while L. monocytogenes was inhibited at pH 6.5 and above. The antimicrobial efficacy of protamine decreased in the presence of negatively charged gelatine B but remained almost unchanged with addition of the positively charged gelatine A. Binding studies showed that the amount of protamine adsorbed to culture media components in tryptic soy broth and bacterial cells increased with increasing pH values. The increased efficacy of protamine at alkaline pH may be explained on the basis of an increase in electrostatic affinity for the cell surface of target cells. E. coli produced a protamine-degrading enzyme, however, was still susceptible to protamine.     

Sinorhizobium meliloti genes involved in tolerance to the antimicrobial peptide protamine

The innate resistance of plants and animals to microbial infection is mediated in part by small cationic peptides with antimicrobial activity. We assessed the susceptibility of the alfalfa symbiont Sinorhizobium meliloti to the model antimicrobial peptide protamine. Twenty-one Tn5-induced mutants showing increased sensitivity to protamine were isolated, and nine were further characterized in detail. These nine mutants carried distinct transposon insertions that affected a total of seven different genes. Three of these genes are involved in exopolysaccharide and beta-(1,2)-glucan biosynthesis (exoT, exoU and ndvB), three other genes are implicated in nitrogen metabolism, such as a putative dyhidropyrimidinase, hutU and ureF, and the last gene exhibited similarity to the ATP binding cassette family of membrane transporters. Symbiotic defects ranging from severe to moderate were displayed by some of the protamine-hypersensitive mutants suggesting that S. meliloti possess active mechanisms to counteract hypothetical cationic peptides that may be produced by its host plant.     

Identification of OmpT as the Protease That Hydrolyzes the Antimicrobial Peptide Protamine before It Enters Growing Cells of Escherichia coli

The influence of extracytoplasmic proteases on the resistance of Escherichia coli to the antimicrobial peptide protamine was investigated by testing strains with deletions in the protease genes degP, ptr, and ompT. Only ΔompT strains were hypersusceptible to protamine. This effect was abolished by plasmids carrying ompT. Both at low and at high Mg²⁺ concentrations, ompT⁺ strains cleared protamine from the medium within a few minutes. By contrast, at high Mg²⁺ concentrations, protamine remained present for at least 1 h in the medium of an ompT strain. These data indicate that OmpT is the protease that degrades protamine and that it exerts this function at the external face of the outer membrane.     

A Salmonella protein that is required for resistance to antimicrobial peptides and transport of potassium.

The ability of invading pathogens to proliferate within host tissues requires the capacity to resist the killing effects of a wide variety of host defense molecules. sap mutants of the facultative intracellular parasite Salmonella typhimurium exhibit hypersensitivity to antimicrobial peptides, cannot survive within macrophages in vitro and are attenuated for mouse virulence in vivo. We conducted a molecular genetic analysis of the sapG locus and showed that it encodes a product that is 99% identical to the NAD+ binding protein TrkA, a component of a low-affinity K+ uptake system in Escherichia coli. SapG exhibits similarity with other E. coli proteins implicated in K+ transport including KefC, a glutathione-regulated efflux protein, and Kch, a putative transporter similar to eukaryotic K+ channel proteins, sapG mutants were killed by the antimicrobial peptide protamine in the presence of both high and low K+, indicating that protamine hypersensitivity is not due to K+ starvation. Strains with mutations in sapG and either sapJ or the sapABCDF operon were as susceptible as sapG single mutants, suggesting that the proteins encoded by these loci participate in the same resistance pathway. SapG may modulate the activities of SapABCDF and SapJ to mediate the transport of peptides and potassium.     

mig-14 is a Salmonella gene that plays a role in bacterial resistance to antimicrobial peptides

It was previously demonstrated that the mig-14 gene of Salmonella enterica serovar Typhimurium is necessary for bacterial proliferation in the liver and spleen of mice following intragastric inoculation and that mig-14 expression, which is induced within macrophages, is under the control of the global regulator PhoP. Here we demonstrate that the mig-14 promoter is induced by growth in minimal medium containing low magnesium or acidic pH, consistent with regulation by PhoP. In addition, mig-14 is strongly induced by polymyxin B, protamine, and the mammalian antimicrobial peptide protegrin-1. While phoP is necessary for the induction of mig-14 in response to protamine and protegrin, mig-14 is still induced by polymyxin B in a phoP background. We also demonstrate that mig-14 is necessary for resistance of S. enterica serovar Typhimurium to both polymyxin B and protegrin-1. Gram-negative resistance to a variety of antimicrobial peptides has been correlated with modifications of lipopolysaccharide structure. However, we show that mig-14 is not required for one of these modifications, the addition of 4-aminoarabinose to lipid A. Additionally, sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis of wild-type and mig-14 lipopolysaccharide also shows no detectable differences between the two strains. Therefore, mig-14 contributes to Salmonella resistance to antimicrobial peptides by a mechanism that is not yet fully understood.     

常用食品防腐剂抗菌作用的研究

采用杯碟法和琼脂平板点种法分别测定２０种常用食品防腐剂对３０株菌的抑菌圈直径和最低抑菌浓度,借此判断药剂抗菌力的大小。实验结果表明,在所测２０种防腐剂中,对细菌抑制力最强者是乙酸,对霉菌和酵母菌抑制力最强者是富马酸二甲酯。