重症肺炎新生儿肠道菌群特征和应激反应及益生菌干预的效果CSCD

目的研究重症肺炎新生儿肠道菌群特征、应激反应及益生菌干预的效果,为此类患儿的治疗提供参考。方法选取2019年1月至2020年3月我院收治的105例重症肺炎新生儿作为试验组,并选取我院产科48例健康新生儿作为对照组。采用随机数字表法将试验组分为益生菌组(n=53)和常规组(n=52),常规组给予新生儿重症肺炎常规治疗,益生菌组在常规组基础上联合运用益生菌治疗。对比试验组和对照组患儿肠道菌群特征,同时对比益生菌组和常规组患儿治疗前后肠道菌群特征和应激反应指标水平。结果相比于对照组,试验组患儿肠道乳杆菌(t=15.454,P<0.001)、肠球菌(t=23.191,P<0.001)、大肠埃希菌(t=25.274,P<0.001)数量显著升高,双歧杆菌数量显著降低(t=46.012,P<0.001)。治疗后,两组患儿肠道乳杆菌、肠球菌、大肠埃希菌数量均降低,双歧杆菌数量升高,且相比于常规组,益生菌组患儿肠道乳杆菌(t=3.617,P<0.001)、肠球菌(t=7.826,P<0.001)、大肠埃希菌数量显著降低(t=5.799,P<0.001),双歧杆菌数量显著升高(t=12.750,P<0.001)。治疗后,两组患儿总抗氧化能力(T-AOC)、超氧化物歧化酶(SOD)水平均升高,丙二醛(MDA)水平降低;且相比于常规组,益生菌组T-AOC(t=18.302,P<0.001)、SOD(t=8.639,P<0.001)水平显著升高,MDA水平显著降低(t=22.816,P<0.001)。结论重症肺炎新生儿肠道菌群主要以乳杆菌、肠杆菌、大肠埃希菌数量升高,双歧杆菌数量降低为特征。益生菌治疗能有效恢复患儿肠道菌群稳定,改善患儿应激反应。     

乳酸链球菌素对瘤胃体外发酵、甲烷生成及功能菌群数量的影响北大核心CSCD

【目的】旨在通过体外静态模拟瘤胃发酵法研究乳酸链球菌素(NI)对瘤胃发酵、甲烷生成及功能菌群数量的影响。【方法】以不添加任何添加剂处理做阴性对照(NC),以莫能菌素(MON,5μmol/L)做阳性对照,试验组NI添加水平分别为3(NI-3)、9(NI-9)和27 mg/100 m L(NI-27),每个处理4个重复,分别于培养后的0、3、6、9、12、24 h测定产气量和甲烷产量。培养24 h后,采集发酵液样品,用于发酵参数和菌群数量的测定。【结果】与NC组相比,添加NI和MON均能显著降低产气量和甲烷产量(P<0.05);添加NI对pH值、干物质消失率(DMD)和有机物消失率(OMD)无显著影响(P>0.05);NI-9处理组与NC组相比氨态氮浓度显著降低(P<0.05),而NI-3和NI-27组氨氮浓度没有显著变化(P>0.05);相比而言,MON处理组DMD、OMD和氨氮浓度与NC组相比均显著降低(P<0.05),而pH值与其他各处理组相比没有差异(P>0.05);与NC组相比,NI各处理组和MON组乙酸浓度及乙丙比均显著降低(P<0.05),丙酸浓度显著提高(P<0.05)。功能菌方面,qPCR结果显示添加NI和MON对总菌和拟杆菌门数量均无显著影响(P>0.05);与NC相比,添加NI对原虫、甲烷菌、真菌和厚壁菌门数量均无显著影响(P>0.05),而MON组原虫、甲烷菌、真菌和厚壁菌门数量显著降低(P<0.05);NI和MON处理均显著提高了硫还原菌和C.aminophilum数量(P<0.05),但C.sticklandii数量不受影响(P>0.05)。【结论】添加适宜浓度的NI可降低瘤胃甲烷与氨的生成,但并不影响饲料消化,这种发酵模式的改变可能与瘤胃功能菌群数量与多样性的变化密切相关。     

土壤生物消毒对番茄青枯病的防控、土壤理化特性和微生物群落的影响

为探索土传病害番茄青枯病防治的有效途径,通过盆栽实验研究了土壤添加米糠及灌水厌氧处理方法对青枯病的控制效果和土壤理化特性的影响。结果表明:与对照(CK)相比,添加2.0%米糠(B)、添加2.0%米糠+淹水(DB)和添加2.0%米糠+密闭厌氧(ADB)对青枯病的防效分别为82.5%、90%和100%,且ADB处理对番茄株高、茎粗和鲜重分别提高176%、111%和755%;3种处理对土壤理化特性也产生了影响,其中DB和ADB处理显著提高土壤温度、pH和电导率(EC),降低氧化还原电位(Eh),而且ADB还明显提高土壤中琥珀酸、反丁烯二酸和柠檬酸的含量;此外,DB和ADB处理减少土壤细菌、放线菌和真菌数量,但显著增加细菌/真菌、细菌/放线菌的比例,同时还显著降低土壤和植株中青枯菌数量。研究表明,DB和ADB两种厌氧处理均能显著改善土壤理化特性和调控微生物群落结构,抑制青枯菌和减少番茄青枯病的发生。     

阿魏酸对高脂血症小鼠肝脂肪变性及肠道菌群的调节作用

目的探讨阿魏酸(ferulic acid)对高脂血症小鼠肝脂肪变性及肠道菌群的调节作用。方法将24只6周龄雄性Apo E-/-小鼠随机分为4组(n=6),即对照组、模型组、阿魏酸组[40 mg/(kg·d)]、辛伐他汀组[5 mg/(kg·d)];另取6只同龄C57BL/6小鼠为空白组。高脂喂养12周后,再给药处理12周,采集小鼠粪便进行肠道菌群检测,检测血脂水平,制作肝切片观察病理变化。结果与对照组相比,模型组小鼠体重、血清总胆固醇(total cholesterol,TC)、甘油三酯(triglyceride,TG)、低密度脂蛋白(low-density lipoprotein cholesterol,LDL-C)明显升高(P 0. 05),肝切片可见小鼠肝细胞质内充满脂滴,大部分肝细胞呈现脂肪变性,模型组厚壁菌门(Firmicutes)和韦荣球菌科(Erysipelotrichaceae)的细菌数量升高,拟杆菌门(Bacteroidetes)、瘤胃菌科(Ruminococcaceae)和Odoribacter数量减少;与模型组比较,阿魏酸组小鼠体重、血清TC、TG、LDL-C显著降低,肝脂肪变性明显减轻,厚壁菌门和韦荣球菌科细菌数量减少,拟杆菌门、瘤胃菌科和Odoribacter数量升高。结论阿魏酸可以改善小鼠的血脂异常,肝脂肪变性,调节肠道菌群失衡。     

基于盲肠菌群和回肠粘膜基因表达探讨解淀粉芽孢杆菌提高蛋鸡生产性能的潜在机制

【背景】我们的前期工作表明,在蛋鸡饲料中添加解淀粉芽孢杆菌BLCC1-0238可显著提高产蛋性能和蛋品质,但其益生机制还不清楚。【目的】从基因组学和转录组学的视角去揭示益生菌提高蛋鸡生产性能的潜在机制。【方法】利用高通量测序技术比较分析基础日粮组(C组)和解淀粉芽孢杆菌BLCC1-0238添加组(0.06%,2.0×1010 CFU/g,T组)盲肠微生物菌群和回肠粘膜基因表达的差异。【结果】基因组学分析发现,与对照组相比,益生菌添加组的盲肠菌群Chao1和Shannon指数升高;在门水平上,厚壁菌门/拟杆菌门(Firmicutes/Bacteroidetes)的比例显著增加,梭杆菌门(Fusobacteria)和变形菌门(Proteobacteria)的相对丰度降低;在属水平上,厚壁菌门中的考拉杆菌属(Phascolarctobacterium)、乳酸杆菌属(Lactobacillus)、瘤胃球菌科UCG-014属(Ruminococcaceae UCG-014)、厌氧棍状菌属(Anaerotruncus)、瘤胃梭菌属(Ruminiclostridium9)、克里斯滕森氏菌(Christensenellaceae_R-7_group)相对丰度明显增加。转录组学结果表明,回肠粘膜组织中共有356个差异表达基因,其中,上调基因199个,下调基因157个。生物信息学分析提示,上调基因参与了淀粉和蔗糖代谢、半乳糖代谢以及甘氨酸、丝氨酸和苏氨酸代谢等促进物质代谢和营养吸收的过程。【结论】日粮中添加解淀粉芽孢杆菌BLCC1-0238,可通过改善盲肠菌群多样性和肠道营养吸收能力提高蛋鸡的饲料利用率和产蛋性能,具有潜在的实用价值。     

溶菌酶对瘤胃体外发酵、甲烷生成及微生物菌群结构的影响

【目的】通过体外静态模拟瘤胃发酵法研究溶菌酶对瘤胃发酵、甲烷生成及微生物菌群结构的影响。【方法】采用单因素多水平试验设计,溶菌酶添加水平分别为0(L-0,对照组)、0.1 mg/100 m L(L-0.1)、1 mg/100 m L(L-1)、10 mg/100 m L(L-10)和100 mg/100 m L(L-100),定时测定产气量和甲烷产量,培养24 h后,发酵液用于发酵参数和微生物菌群数量的q PCR测定,其中L-0、L-1和L-100三个组发酵液同时进行16S r RNA基因Illumina高通量测序。【结果】与对照组相比,低剂量溶菌酶添加(L-0.1组)不影响甲烷产量、氨氮浓度、干物质消失率、有机物消失率和总挥发性脂肪酸等瘤胃发酵参数(P0.05);随着剂量提高,L-1处理组甲烷产量、氨氮浓度显著降低(P0.05),丙酸浓度显著增加(P0.05),并且干物质消失率、有机物消失率和总挥发性脂肪酸不受影响(P0.05);而较高剂量组(L-10和L-100组)虽然甲烷产量显著降低,丙酸浓度显著增加(P0.05),但干物质消失率和有机物消失率也显著降低(P0.05)。q PCR结果显示高剂量组(L-100组)总菌、原虫、甲烷菌数量与对照组相比显著降低(P0.05),而L-0.1、L-1和L-10组总菌、真菌和原虫数量与对照组相比均无显著变化(P0.05)。高通量测序主成分分析(PCA)显示对照组与溶菌酶添加组间瘤胃细菌组成的明显区分,说明添加溶菌酶显著改变了瘤胃细菌菌群结构。溶菌酶通过增加月形单胞菌和琥珀酸弧菌等丙酸生成菌的相对丰度,使更多的氢被用于生成丙酸,导致甲烷产量降低;溶菌酶可抑制普雷沃氏菌和拟杆菌属等蛋白降解菌的生长,进而减少蛋白质过度降解,降低氨氮浓度。【结论】添加适宜浓度(1 mg/100 m L)的溶菌酶可通过调控瘤胃微生态改变瘤胃发酵模式,降低瘤胃甲烷和氨的生成,短期内并不影响饲料消化。     

原生质体融合构建高效产脂肽工程菌

芽孢杆菌因其可产生多种生理活性物质,在环境污染修复、生物防治、微生物采油等领域具有广阔的应用前景。莫哈韦芽孢杆菌Bacillus mojavensis JF-2和解淀粉芽孢杆菌B. amyloliquefaciens BQ-6是从油田筛选出的产脂肽类表面活性剂菌株, 但在微生物采油实际应用中受到氧气浓度、盐度及pH的限制。原生质体融合是改变微生物代谢功能的一种简便有效的方法,以上述两株芽孢杆菌为对象,利用4因素3水平正交试验来探索菌龄、溶菌酶浓度、酶解温度和酶解时间对原生体制备、再生的影响。此外,对两菌株进行了双亲灭活原生质体融合,通过筛选得到了一株工程菌HY-4,并对其进行了初步的评价。结果表明:菌龄、溶菌酶浓度和酶解时间显著影响芽孢杆菌原生质体制备率及再生率(P<0.05),且在溶菌酶处理前用生理盐水多次洗涤菌体细胞,可提高制备率。两种芽孢杆菌原生质体制备及再生的最优条件均为:菌龄7 h、溶菌酶浓度2.5 mg/ml、酶解时间30 min、酶解温度42 ℃。融合子HY-4的最高耐盐度为15%,可耐50 ℃高温,代谢产脂肽的pH范围为4.0~9.5,且在好氧及厌氧条件下均能够代谢产脂肽,在厌氧条件下生长迅猛(细胞干重>1.6 g/L)。综上所述,融合子HY-4具有较大的应用潜力,该研究为芽孢杆菌的遗传育种打下了方法学基础,并对驱油微生物菌种的选育具有指导意义。     

氮磷钾添加对罗汉松土壤微生物功能多样性的影响

为揭示罗汉松土壤微生物对不同氮磷钾养分水平的响应及规律,该研究以两年生罗汉松(Podocarpus macrophyllus)幼苗为试验树种,采用L9正交试验控制盆栽土壤的氮磷钾养分水平梯度,使用稀释平板涂布法和Biolog-ECO微平板法探讨不同土壤氮磷钾养分水平对罗汉松土壤微生物量和群落多样性及其对6种碳源的利用特征。结果表明:(1)随氮添加量的增加,土壤细菌(P<0.05)和放线菌数量(P<0.001)减少,真菌(P<0.001)及固氮菌数量(P<0.01)显著增加,土壤微生物群落的Pielou 指数(P<0.001)降低,Simpson指数(P<0.05)和McIntosh指数(P<0.001)升高,从而降低了土壤微生物对6种碳源的利用强度,特别是对难利用碳源胺类(P<0.001)、羧酸(P<0.001)、聚合物(P<0.001)及其他化合物(P<0.001)的利用强度显著降低。(2)磷添加量的增加显著降低了土壤微生物群落的Shannon指数(P<0.05)。(3)钾添加量的增加显著降低了土壤微生物群落的Shannon指数和Pielou指数及微生物群落对碳水化合物和氨基酸(P<0.01)两类易利用碳源的强度。综上所述,氮添加和钾添加是影响罗汉松土壤微生物群落功能多样性的主要因素,在罗汉松培育时应注意少量多次施肥,降低氮和钾的添加量,适当提高磷添加量,以促进罗汉松的生长及其可持续培育。该研究从微生物的角度为罗汉松施肥及管护提供了理论依据。     

急性呼吸窘迫综合征新生儿肠道菌群特征及其对免疫功能的影响

目的 研究急性呼吸窘迫综合征(ARDS)新生儿肠道菌群特征及其对免疫功能的影响。方法 采用前瞻性研究方法,以我院2017年1月至2021年1月诊断的新生儿急性呼吸窘迫综合征患儿120例作为研究对象,其中轻度患儿39例,中度患儿45例,重度患儿36例,另选取同期出生的健康新生儿120例作为对照组,收集患儿的粪便样本并保存于厌氧菌稀释液,使用MRS琼脂培养基、KF琼脂培养基、马丁培养基检测肠道双歧杆菌、肠球菌、乳杆菌以及真杆菌的数量,比较各类患儿肠道菌群、免疫指标的差异。结果 观察组患儿肠道双歧杆菌(t=16.217,P<0.001)、肠球菌(t=10.677,P<0.001)、乳杆菌(t=8.326,P<0.001)以及真杆菌(t=12.455,P<0.001)数量显著低于对照组。轻度组、中度组以及重度组患儿肠道双歧杆菌(F=13.069,P<0.001)、肠球菌(F=10.269,P<0.001)、乳杆菌(F=12.036,P<0.001)以及真杆菌(F=10.698,P<0.001)数量之间的差异有统计学意义。患儿出生后第10天肠道乳杆...     

高效厌氧纤维素降解细菌的分离及酶特性研究

采用透明圈初筛和滤纸降解率复筛的方法从内蒙古绵羊瘤胃内容物中分离到高效厌氧纤维素降解细菌4株.通过形态学、生理生化反应、生态特性和遗传型的鉴定,所分离的4株菌WHQ、LYQ、LBG-1和NDF-3分别归为溶纤维丁酸弧菌(Butyrivibrio fibrisollvens)、黄色瘤胃球菌(Ruminococcus flavefaciens)、产琥珀酸丝状杆菌(Fibrobacter succinogenes)和解多糖梭菌(Clostridium polysaccharolyticum).测定了4株菌对滤纸的降解率,WHQ、LYQ、LBG-1和NDF-3的2周滤纸降解率分别为25.1%、14.3%、21.0%和20.6%.本研究同时对4株菌的滤纸酶活力、羧甲基纤维素酶活力和β-葡萄糖苷酶活力进行了测定.     

Effects of malic acid on rumen fermentation, urinary excretion of purine derivatives and feed digestibility in steers

The objective of this study was to evaluate the effects of malic acid (MA) supplementation on rumen fermentation, urinary excretion of purine derivatives (PDs) and whole gastro-intestinal tract feed digestibility in steers. Eight ruminally cannulated Simmental steers (465 ± 13 kg) were used in a replicated 4 × 4 Latin square design. The treatments were: control (without MA), LMA (MA-low), MMA (MA-medium) and HMA (MA-high) with 0.0, 7.8, 15.6 and 23.4 g MA per kg dry matter (DM), respectively. Diets consisted of corn stover and concentrate (60/40, DM basis). DM intake was approximately 9 kg per day, which was 90% of ad libitum intake including 5.4 kg corn stover and 3.6 kg concentrate. Ruminal pH (range of 6.91 to 6.56), ratio of acetate to propionate (range of 3.88 to 3.25), ammonia N (range of 9.03 to 6.42 mg/100 ml) and lactate (range of 91.25 to 76.31 mg/100 ml) decreased linearly as MA supplementation increased, whereas total volatile fatty acid (VFA) concentration (range of 55.68 to 61.49 mM) linearly (P < 0.05) increased with increase in MA supplementation. In situ ruminal neutral detergent fiber (aNDF) degradation of corn stover was improved but the crude protein (CP) degradability of concentrate mix was decreased with increasing the dose of MA. Urinary excretion of PDs was quadratically (P < 0.01) changed with altering MA supplementation (67.88, 72.74, 75.81 and 73.78 mmol/day for control, LMA, MMA and HMA, respectively). Similarly, digestibilities of DM, organic matter (OM), NDF and acid detergent fiber (ADF) in the total tract were also quadratically increased with increasing MA, and no differences in terms of CP and ether extract digestibility were observed. The results indicate that MA supplementation has the potential to improve rumen fermentation and feed digestion in beef cattle. The MA stimulates the digestive microorganisms or enzymes in a quadratic response. In the experimental conditions of this trial, the optimum MA dose was 15.6 g MA per kg DM.     

外源茉莉酸诱导的青杨叶片保护性酶活性变化及其对舞毒蛾幼虫生长发育的影响

为探讨外源茉莉酸对青杨Populus cathayana的诱导抗性及其对舞毒蛾Lymantria dispar的影响, 室内对青杨扦插苗喷施不同浓度的茉莉酸（对照为0.17%丙酮）, 分别在喷施后1, 5和10 d采集叶片分析其保护性酶活性的变化, 并接舞毒蛾幼虫于青杨苗木上观测其长发育情况。结果表明： 0.1 和0.001 mmol/L两种浓度的茉莉酸（JA）处理均使青杨叶过氧化物酶（POD）、 多酚氧化酶（PPO）、 苯丙氨酸解氨酶（PAL）、 胰凝乳蛋白酶抑制剂（CI）和胰蛋白酶抑制剂（TI）活性较对照增加(P<0.05)。取食茉莉酸诱导的青杨苗木后, 舞毒蛾幼虫的发育历期延长, 体重降低。0.1 mmol/L茉莉酸诱导的青杨苗木5 d后接虫, 使舞毒蛾幼虫的发育历期显著延长, 较对照长8 d; 接虫21 d后称重时, 取食茉莉酸诱导的青杨叶片的幼虫体重较对照组降低了50%~100%, 该结果说明外源茉莉酸诱导青杨产生了对舞毒蛾明显的抗虫性。     

Biohydrogenation of linoleic acid by rumen fungi compared with rumen bacteria

AIMS: To investigate biohydrogenation of linoleic acid by rumen fungi compared with rumen bacteria, and to identify the fungus with the fastest biohydrogenation rate. METHODS AND RESULTS: Biohydrogenation of linoleic acid by mixed rumen fungi and mixed rumen bacteria were compared in vitro. With mixed rumen bacteria, all biohydrogenation reactions were finished within 100 min of incubation and the end product of biohydrogenation was stearic acid. With mixed rumen fungi, biohydrogenation proceeded more slowly over a 24-h period. Conjugated linoleic acid (CLA; cis-9, trans-11 C18 : 2) was an intermediate product, and vaccenic acid (VA; trans-11 C18 : 1) was the end product of biohydrogenation. Fourteen pure fungal isolates were tested for biohydrogenation rate. DNA sequencing showed that the isolate with the fastest rate belonged to the Orpinomyces genus. CONCLUSIONS: It is concluded that rumen fungi have the ability to biohydrogenate linoleic acid, but biohydrogenation is slower in rumen fungi than in rumen bacteria. The end product of fungal biohydrogenation is VA, as for group A rumen bacteria. Orpinomyces is the most active biohydrogenating fungus. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first study to demonstrate that rumen fungi can biohydrogenate fatty acids. Fungi could influence CLA content of ruminant products.     

The influence of extracellular hydrogen on the metabolism of Bacteroides ruminicola, Anaerovibrio lipolytica and Selenomonas ruminantium

Strains of three anaerobic rumen bacteria, Bacteroides ruminicola, Anaerovibrio lipolytica and Selenomonas ruminantium, were able to use extracellular H2 to reduce fumarate to succinate. Each bacterium possessed membrane-bound hydrogenase and fumarate reductase activity. Membrane-bound cytochrome b was reducible by H2 and oxidizable by fumarate in each bacterium. The apparent Km values for hydrogen of the hydrogenases were 4 . 5 x 10(-6) M, 1 . 4 x 10(-5) M and 4 . 4 x 10(-5) M for B. ruminicola, A. lipolytica and S. ruminantium, respectively. The apparent Km values for fumarate of the fumarate reductases were approximately 1 . 0 x 10(-4) M for each bacterium.     

Diet-dependent shifts in the bacterial population of the rumen revealed with real-time PCR

A set of PCR primers was designed and validated for specific detection and quantification of Prevotella ruminicola, Prevotella albensis, Prevotella bryantii, Fibrobacter succinogenes, Selenomonas ruminantium-Mitsuokella multiacida, Streptococcus bovis, Ruminococcus flavefaciens, Ruminobacter amylophilus, Eubacterium ruminantium, Treponema bryantii, Succinivibrio dextrinosolvens, and Anaerovibrio lipolytica. By using these primers and the real-time PCR technique, the corresponding species in the rumens of cows for which the diet was switched from hay to grain were quantitatively monitored. The dynamics of two fibrolytic bacteria, F. succinogenes and R. flavefaciens, were in agreement with those of earlier, culture-based experiments. The quantity of F. succinogenes DNA, predominant in animals on the hay diet, fell 20-fold on the third day of the switch to a grain diet and further declined on day 28, with a 57-fold reduction in DNA. The R. flavefaciens DNA concentration on day 3 declined to approximately 10% of its initial value in animals on the hay diet and remained at this level on day 28. During the transition period (day 3), the quantities of two ruminal prevotella DNAs increased considerably: that of P. ruminicola increased 7-fold and that of P. bryantii increased 263-fold. On day 28, the quantity of P. ruminicola DNA decreased 3-fold, while P. bryantii DNA was still elevated 10-fold in comparison with the level found in animals on the initial hay diet. The DNA specific for another xylanolytic bacterium, E. ruminantium, dropped 14-fold during the diet switch and was maintained at this level on day 28. The concentration of a rumen spirochete, T. bryantii, decreased less profoundly and stabilized with a sevenfold decline by day 28. The variations in A. lipolytica DNA were not statistically significant. After an initial slight increase in S. dextrinosolvens DNA on day 3, this DNA was not detected at the end of the experiment. S. bovis DNA displayed a 67-fold increase during the transition period on day 3. However, on day 28, it actually declined in comparison with the level in animals on the hay ration. The amount of S. ruminantium-M. multiacida DNA also increased eightfold following the diet switch, but stabilized with only a twofold increase on day 28. The real-time PCR technique also uncovered differential amplification of rumen bacterial templates with the set of universal bacterial primers. This observation may explain why some predominant rumen bacteria have not been detected in PCR-generated 16S ribosomal DNA libraries.     

Activity and properties of fumarate reductase in ruminal bacteria

Fumarate-reducing bacteria were sought from the main ruminal bacteria. Fibrobacter succinogenes, Selenomonas ruminantium subsp. ruminantium, Selenomonas ruminantium subsp. lactilytica, and Veillonella parvula reduced fumarate by using H(2) as an electron donor. Ruminococcus albus, Prevotella ruminicola, and Anaerovibrio lipolytica consumed fumarate, although they did not oxidize H(2). Of these bacteria, V. parvula, two strains of Selenomonas, and F. succinogenes had a high capacity to reduce fumarate. In all the fumarate-reducing bacteria examined, fumarate reductase existed in the membrane fraction. Based on the activity per cell mass and the affinity of fumarate reductase to fumarate, these bacteria were divided into two groups, which corresponded to the capacity to use H(2): A group of bacteria with higher activity and affinity were able to use H(2) as an electron donor for fumarate reduction. The bacteria in this group should gain an advantage over the bacteria in another group in fumarate reduction in the rumen. Cellulose digestion by R. albus was improved by fumarate reduction by S. lactilytica as a result of an increased growth of R. albus, which may have been caused by the fact that S. lactilytica immediately consumed H(2) produced by R. albus. Thus fumarate reduction may play an important role in keeping a low partial pressure of H(2) in the rumen.     

The Effect of Monensin on Pure and Mixed Cultures of Rumen Bacteria

The antibiotic monensin was added to pure cultures of Bacteroides ruminicola, Selenomonas ruminantium, Anaerovibrio lipolytica and Megasphaera elsdenii. These organisms, representing succinate- and propionate-producing rumen bacteria, were not affected by monensin up to 10 μg/ml. Methanobacterium ruminantium was slightly inhibited by monensin, Butyrivibrio fibrisolvens, Ruminococcus albus and Streptococcus bovis were inhibited to differing extents by monensin at concentrations between 0.1 and 10 μg/ml. Bacteroides succinogenes was inhibited at first by monensin at >0.5 μg/ml but after a prolonged lag phase adapted to grow in the presence of monensin at concentrations below 5 μg/ml.
Monensin (1 μg/ml) almost completely stopped the digestion of chopped straw and dewaxed cotton fibres by rumen contents incubated in vitro. The digestion of grass and powdered filter paper was not significantly reduced under these conditions, but when the concentration of monensin was increased to between 3 and 5 μg/ml, the digestion of these substrates was reduced.     

基于对JNK信号通路的调控探讨齐墩果酸对食管癌细胞凋亡的影响

摘要 目的：本研究通过对JNK信号通路的调控来探讨齐墩果酸( oleanolic acid,OA) 对食管癌细胞凋亡的影响。方法：对食管癌细胞EC109进行培养,以MTT法分析不同浓度齐墩果酸对食管癌细胞EC109的生长抑制作用,采用流式细胞术考察齐墩果酸对EC109细胞凋亡的影响,以Western blot实验检测JNK通路蛋白的表达情况。结果：不同浓度齐墩果酸作用Eca109细胞48 h后,均有显著的抑制作用（P<0.05）,且随着齐墩果酸浓度的增加,对Eca109的抑制作用逐渐增强。与对照组相比,各浓度OA组的Eca109细胞的凋亡率分别为8.03±0.34 %,12.82±0.28 %,19.34±0.79 %和32.21±0.81 %,均显著增加（P<0.05）,且随着OA浓度的增加,细胞凋亡率显著升高。与对照组相比,不同浓度OA组的P-JNK、Bak、Bax表达量均显著升高（P<0.05）,Bcl-2表达量显著降低（P<0.05）,JNK表达量无显著差异（P>0.05）,对OA组(1.2 mmol/L)相比,OA组(2.4 mmol/L) Bak、Bax表达量均显著升高（P<0.05）,Bcl-2表达量显著降低（P<0.05）,P-JNK、JNK表达量无显著差异（P>0.05）。结论：齐墩果酸能通过对JNK信号通路的调控促进食管癌细胞的凋亡,且随着浓度的增强,细胞凋亡率显著升高。     

Biohydrogenation of C18 unsaturated fatty acids to stearic acid by a strain of Butyrivibrio hungatei from the bovine rumen

AIMS: To identify a ruminal isolate which transforms oleic, linoleic and linolenic acids to stearic acid and to identify transient intermediates formed during biohydrogenation. METHODS AND RESULTS: The stearic acid-forming bacterium, isolated from the rumen of a grazing cow, was a Gram-negative motile rod which utilized a range of growth substrates including starch and pectin but not cellulose or xylan. From its 16S rRNA gene sequence, the isolate was identified as a strain of Butyrivibrio hungatei. During conversion of linoleic acid, 9,11-conjugated linoleic acid formed as a transient intermediate before trans-vaccenic acid accumulated together with stearic acid. Unlike previously studied ruminal biohydrogenating bacteria, B. hungatei Su6 was able to convert alpha-linolenic acid to stearic acid. Linolenic acid was converted to stearic via conjugated linolenic acid, linoleic acid and trans-vaccenic acid as intermediates. Oleic acid and cis-vaccenic acid were converted to a series of trans monounsaturated isomers as well as stearic acid. An investigation of these isomers indicated that mixed trans positional isomers are intermediate in the biohydrogenation of cis monounsaturated fatty acids to stearic acid. CONCLUSION: This, the first rigorous identification and characterization of a ruminal bacterium which forms stearic acid, shows that B. hungatei plays an important role in unsaturated fatty acid transformations in the rumen. SIGNIFICANCE AND IMPACT OF THE STUDY: Biohydrogenating bacteria which convert C18 unsaturated fatty acids to stearic acid have not been available for study for many years. Access to B. hungatei Su6 now provides a fresh opportunity for understanding biohydrogenation mechanisms and rumen processes which lead to saturated fat in ruminant products.     

Effects of protozoa on Methane production in rumen and hindgut of calves around time of weaning

Effects of the presence or absence of ciliate protozoa on methanogenesis in the rumen and hindgut were investigated in young calves during a 7-week period. Ten Holstein calves, aged 7 days, were divided in two groups (n = 5) and fed an increasing amount of a commercial milk replacer and small amounts of a calves starter. One group was inoculated with ciliate fauna on two occasions, week 5 and 6, while the second remained ciliate-free. The absence of protozoa in the rumen decreased rumen empty weight ( ? 23%, P < 0.01), and rumen pool size of N ( ? 36%, P < 0.01) and crude fat ( ? 37%, P < 0.05). Rumen bacteria of non-faunated calves contained a higher proportion of total amino acid-N per 16 g N ( + 3%, P < 0.01) and D-alanine-N per 16 g N ( + 13%, P < 0.05) compared to faunated calves. Further results contain a reference for a higher bacterial mass in the ciliate-free rumen with an increased number of bacteria adherent to rumen mucosa. The CH₄ production in the rumen increased exponentially with the increase in protozoa population size (R² = 0.68). In presence of 46 · 10⁴ protozoa per ml rumen fluid, the in vitro CH₄ production of rumen fluid per mol total VFA was about 34% higher in faunated than in non-faunated calves (P < 0.001). Hydrogen (2H) recovery of rumen fermentation was positively correlated (R² = 0.55) to the CH₄ production rate. Methanogens were attached on rumen mucosa. Methanogenesis, induced by rumen mucosa attached bacteria, was stimulated by ruminal protozoa. In the absence of protozoa in the rumen, the acetate - propionate ratio and butyrate proportion of VFA were reduced. In vivo in the absence of protozoa not only the whole animal CH₄ production ( ? 30%, P < 0.05) but also the digestibility of carbohydrates ( ? 4%, P < 0.05) was reduced. Thereby no difference was observed in the intake of ME per kg DM between the groups. In conclusion, the methanogenesis in the rumen, but not in hindgut, is associated with the development of the ruminal protozoa population. The level of methanogenesis (mol/mol VFA) in the hindgut amounts to 20% of the ruminal methanogenesis.