人工瘤胃技术的研究及其进展

人工瘤胃技术的创立人是Tappeiner, 早在1882年他就开始应用所谓的“人工瘤胃”研究公牛瘤胃细菌对纤维素的消化作用,并发现有大量挥发性脂肪酸(VFA)产生。1938年,Woodman和Vans首次发现葡萄糖是纤维素消化的中间产物,乳酸和VFA则是终产物。1943年,Pearson和Smith在培养加有尿素、磷酸氢二钾、葡萄糖和硫酸亚铁的瘤胃液后,发现瘤胃微生物能利用尿素     

改善瘤胃微生物转化效率增进反刍家畜生产力

牛、羊的营养物质消化和利用取决于瘤胃微生物的作用。瘤胃微生物对牛、羊的营养作用主要表现在:①能分解粗纤维,牛、羊能消化饲料中的粗纤维达50—80％;②能把植物性饲料中的低质蛋白转变成高质微生物蛋白,甚至能利用非蛋白氧(如尿素)合成高质菌体蛋白;③合成维生素R复合体及维生素K;④还能合成牛、羊所需的十种必需氨基酸,并能将牧草中的不炮和脂肪酸转变成牛、羊体内的饱和脂肪酸。Smith等(1977)认为,提高家畜生产力的途径将包括利用遗传调节瘤胃细菌以控制瘤胃生态系。任何不利于瘤胃微生物的因素,都将影响营养物的转化和利用。     

反刍动物的氮代谢—历史的回顾,当前的认识及今后的展望

反刍动物的氮代谢是很多研究报告的主题。对于瘤胃和肠道功能的研究还在继续进行。许多试验已经表明了瘤胃微生物作为蛋白质来源在数量上和质量上具有重要性。控制微生物蛋白的合成或微生物的生长以及日粮蛋白的降解的各种因素已被揭示出来。关 于向反刍动物提供蛋白质的细节(瘤胃合成、过瘤胃日粮蛋白质、小肠消化)方面的知识已经有了相当的积累。相比之下当前对于反刍动物对氨基酸数量上的需要了解得还很不够。已经提出了一些描述反刍动物氮代谢的模型,这些模型综合了当前有关方面的各种知识。今后随着逐步加以修正,将有助于日粮的配合工作,更加充分地利用瘤胃发酵,提高反刍动物的生产效率。对于反刍动物氯代谢的进一步研究,将会更好地控制瘤胃发酵及瘤胃后的消化过程。     

瘤胃细菌和原虫蛋白的测定方法

在过去几十年里,主要瘤胃微生物已经得到鉴别,其营养需要,生理特性,生化途径和微生物功能已作了大量论述。最后阶段就是把瘤胃作为一个生态体系,要对微生物在混合培养或体内试验中显示其特性的程度作定量和动态分析。达到这一目标,显然要弄清瘤胃微生物既相互依存又竞争的关系。瘤胃微生物之间彼此存在相互制约,相互共生关系。纤毛虫能吞食和消化细菌,除了菌体     

反刍动物蛋白质体系的最新概念

瘤胃产生的微生物蛋白不能满足高产奶牛和快速育肥牛的需要,饲粮中必须有过瘤胃蛋白到小肠以提供充分的氨基酸。因此,合理的蛋白质营养由供给瘤胃和微生物的蛋白质来确定。NRC(1985)用消化区(Pools)和换算系数来描述蛋白质的代谢,并使用了计算机。各区消化的换算系数见表1,用于换算系数的术语限于6个性状,它们是成比例的,为提供一个严谨的计算模式,引入FORTRAN Ⅳ程序计算有关系数。     

鱼粉对瘤胃细菌发酵的影响

在泌乳牛日粮中添加鱼粉(FM)作为过瘤胃蛋白会降低乳脂率。FM含4.5％～10.5％的粗脂肪,其中14％～26％是20以上碳链多烯脂肪酸。虽然微生物脂解活性很高,使瘤胃中游离脂肪酸(FFA)迅速形成,但日粮中所含的未酯化脂肪酸比酯化脂肪酸对瘤胃微生物危害更大。新鲜鱼油中,脂肪酸形成中性脂肪或磷脂,但FM长期存放或变质时,脂肪酸会游离出来。因此,有些FM的FFA含量很高。Storry首先用鳕鱼肝油做了研究,指出日粮脂肪酸可能通过影响瘤胃挥发性脂肪酸(VFA)比例,抑制瘤胃微生物脂肪酸合成;或者因20以上碳链多烯脂     

反刍动物肽代谢的研究进展

肽作为蛋白质的主要消化产物,是反刍动物和瘤胃微生物的重要营养来源。反刍动物的组织及瘤胃微生物都能利用肽作为氮源以维持其生长,且肽显示了比氨基酸更强的刺激瘤胃微生物生长的作用。反刍动物存在对肽和氨基酸不同的并行吸收机制,以确保机体在各种生理状态下的营养代谢的平衡。本文从瘤胃肽的产生和降解机制、吸收和营养作用、代谢调控等方面阐述了反刍动物肽的研究进展。     

反刍动物氨基酸营养的研究进展

一、AA在反刍动物体内的代谢 1.AA在瘤胃内降解与合成 饲料蛋白质在瘤胃内经微生物蛋白酶水解产生肽、AA除少量被细菌摄取外,大部分迅速脱氨基产生NH_3、CO_2和挥发性脂肪酸(VFA)。Chalupa等(1975)用体外法测定AA的降解率证明,亮氨酸(国Leu)、异亮氨酸(Ile)和缬氨酸(Val)的最低;精氨酸(Arg)、赖氨酸(Lys)、苯丙氨酸(Phe)和苏氨酸(Thr)居中;蛋氨酸(Met)最高。将5克Met注入绵羊瘤胃,其半衰期为2.5小时。 瘤胃微生物可利用NH_3合成AA。Loosl等(1949)给绵羊和山羊饲喂仅含尿素的纯     

反刍动物碳水化合物和含氮化合物的消化代谢规律刍议

碳水化合物和含氮化合物是反刍动物营养的重要来源,碳水化合物在瘤胃中降解为挥发性脂肪酸(VFA)和酮酸;含氮化合物降解为NH3和CO2;瘤胃中的微生物利用酮酸和NH3合成MCP,为瘤胃微生物和动物提供能量与蛋白营养。本文从反刍动物碳水化合物和含氮化合物的消化吸收,代谢和营养作用等方面阐述了反刍动物碳水化合物和含氮化合物的规律。     

奶牛饲料的蛋白质来源

奶牛饲料中的粗蛋白质被瘤胃微生物分解成肽、氨基酸以及游离氨。氨和来自饲料及添加的非蛋白氮(NPN)能转化为微生物蛋白质,条件是必须提供充足而又能发酵的碳水化合物。 由于瘤胃微生物蛋白不足以满足高产奶牛的最大产乳量之需要,因此,为达到高水平的产乳量,奶牛还须依赖于饲料中非降解蛋白质(UIP)或称过瘤胃蛋白质。 美国NRC饲养标准(1988年版)中规定了奶牛降解蛋白质(DIP)的推荐量和UIP的需要量。但是,在目前完全按照DIP/UIP方法看来还有些困难,原因是在原料的测试上还不够完善。     

Estimating the postmortem interval using microbes: Knowledge gaps and a path to technology adoption

Microbes have potential to be used as physical evidence for forensic science because they are ubiquitous and have predictable ecologies. With the advent of next generation sequencing technology and the subsequent boost to microbiome science (study of the genes and molecules of microbial communities), it has become possible to develop new microbial-based tools for forensic science. One promising approach is the use of microbial succession during the ecological process of decomposition to estimate the time since death, or postmortem interval (PMI). This microbial clock of death is developed by building a regression model using microbiome data collected from postmortem samples (e.g. swab of skin) with known PMIs. In a death investigation, a similar sample type (e.g. swab of skin) would be collected, the microbes profiled using DNA sequencing, and the microbes would be matched to a point on the clock (i.e. the regression model). Recent research by several independent scientific teams has provided a proof of concept for this new microbiome forensic tool. However, developing and transitioning new forensic science technologies into the justice system requires overcoming scientific, investigative, and legal hurdles. In this article, I address the apparent knowledge gaps in the science of microbiome technology to estimate PMI, and discuss a path for bringing this technology into the justice system.     

Exploring postmortem succession of rat intestinal microbiome for PMI based on machine learning algorithms and potential use for humans

The microbial communities may undergo a meaningful successional change during the progress of decay and decomposition that could aid in determining the post-mortem interval (PMI). However, there are still challenges to applying microbiome-based evidence in law enforcement practice. In this study, we attempted to investigate the principles governing microbial community succession during decomposition of rat and human corpse, and explore their potential use for PMI of human cadavers. A controlled experiment was conducted to characterize temporal changes in microbial communities associated with rat corpses as they decomposed for 30 days. Obvious differences of microbial community structures were observed among different stages of decomposition, especially between decomposition of 0–7d and 9–30d. Thus, a two-layer model for PMI prediction was developed based on the succession of bacteria by combining classification and regression models using machine learning algorithms. Our results achieved 90.48% accuracy for discriminating groups of PMI 0–7d and 9–30d, and yielded a mean absolute error of 0.580d within 7d decomposition and 3.165d within 9–30d decomposition. Furthermore, samples from human cadavers were collected to gain the common succession of microbial community between rats and humans. Based on the 44 shared genera of rats and humans, a two-layer model of PMI was rebuilt to be applied for PMI prediction of human cadavers. Accurate estimates indicated a reproducible succession of gut microbes across rats and humans. Together these results suggest that microbial succession was predictable and can be developed into a forensic tool for estimating PMI.     

航天飞行和模拟微重力下微生物次级代谢研究与太空微生物制药

随着人类对宇宙的不断探索,大量研究观察到微生物次级代谢在航天飞行中的变化,为人类利用太空环境进行高产和高质量微生物制药带来了希望。研究者认为,太空环境下微生物生长停滞期缩短,更早进入生长期,更早产生次级代谢产物。由于空间飞行的稀缺性和高昂成本,研究者利用微重力模拟设备进行微生物次级代谢研究。目前,不同的航天飞行和模拟微重力下微生物次级代谢研究并未观察到趋势相对一致的结果,其表型变化背后的分子生物学机制也有待进一步研究。太空微生物制药利用太空诱变筛选具有商业和医学价值的制药微生物菌株,这种航天飞行后地面筛选的模式具有无法控制诱变方向、被动筛选的缺陷,有待相关诱变通路进一步研究后予以改进。     

单人纯氧舱高压氧对微生物抑制的研究

目的探讨单人纯氧舱高压氧治疗对微生物的抑制。方法模拟实验菌的存在环境,接受模拟的高压氧治疗方案。结果高压氧对厌氧菌有高度抑制作用,对需氧菌和真菌有抑制作用,但对铜绿假单胞菌抑制作用不明显。结论在高压氧舱内有交叉污染的可能。     

Tracing recent outdoor geolocation by analyzing microbiota from shoe soles and shoeprints even after indoor walking

The microbial communities on shoe soles and shoeprints could carry microbial information about where someone walked. This is possible evidence to link a suspect in a crime case to a geographic location. A previous study had shown that the microbiota found on shoe soles depend on the microbiota of the soil on which people walk. However, there is a turnover of microbial communities on shoe soles during walking. The impact of microbial community turnover on tracing recent geolocation from shoe soles has not been adequately studied. In addition, it is still unclear whether the microbiota of shoeprints can be used to determine recent geolocation. In this preliminary study, we investigated whether the microbial characteristics of shoe soles and shoeprints can be used to trace geolocation and whether this information can be destroyed by walking on indoor floors. In this study, participants were asked to walk outdoors on exposed soil, then walk indoors on a hard wood floor. High-throughput sequencing of the 16S rRNA gene was performed to characterize the microbial communities of shoe soles, shoeprints, indoor dust, and outdoor soil. Samples of shoe soles and shoeprints were collected at steps 5, 20, and 50 while walking indoors. The PCoA result showed that the samples were clustered by geographic origin. The shoeprint showed a more rapid turnover of microbial community than the shoe sole during indoor walking. The result of FEAST showed that the microbial communities of shoe sole and shoeprint were mainly (shoe sole, 86.21∼92.34 %; shoeprint, 61.66∼90.41 %) from the soil of the outdoor ground where the individual recently walked, and a small portion (shoe sole, 0.68∼3.33 %; shoeprint, 1.43∼27.14 %) from the indoor dust. Based on the matching of microbial communities between geolocation and shoe sole or shoeprint, we were able to infer the recent geolocation of the individual with relatively high accuracy using the random forest prediction model (shoe sole: 100.00 %, shoeprint: 93.33∼100.00 %). Overall, we are able to accurately infer the geolocation of an individual’s most recent outdoor walk based on the microbiota of shoe sole and shoeprint, even though these microbiotas show a turnover when walking indoor floor. The pilot study was expected to provide a potential method for tracing recent geolocation of suspects.     

反刍动物短期人工瘤胃发酵技术的应用及存在问题

瘤胃发酵体外模拟技术是利用离体方法研究反刍动物瘤胃微生物发酵以及评定日粮营养价值的一项技术。研究瘤胃模拟技术的方法很多，本文综述了短期人工瘤胃发酵技术的应用情况及存在问题。     

Applying microbial biogeography in soil forensics

The ubiquity, heterogeneity and transferability of soil makes it useful as evidence in criminal investigations, especially using new methods that survey the microbial DNA it contains. However, to be used effectively and reliably, more needs to be learned about the natural distribution patterns of microbial communities in soil. In this study we examine these patterns in detail, at local to regional scales (2 m–260 km), across an environmental gradient in three different soil types. Geographic location was found to be more important than soil type in determining the microbial community composition: communities from the same site but different soil types, although significantly different from each other, were still much more similar to each other than were communities from the same soil type but from different sites. At a local scale (25–1000 m), distance-decay relationships were observed in all soil types: the farther apart two soil communities were located, even in the same soil type, the more they differed. At regional-scale distances (1–260 km), differences between communities did not increase with increased geographic distance between them, and the dominant factor determining the community profile was the physico-chemical environment, most notably annual precipitation (R² = 0.69), soil sodium (R² = 0.49) and soil ammonium (R² = 0.47) levels. We introduce a likelihood-ratio framework for quantitative evaluation of soil microbial DNA profile evidence in casework. In conclusion, these profiles, along with detailed knowledge of natural soil microbial biogeography, provide valuable forensic information on soil sample comparison and allow the determination of approximate source location on large (hundreds of km) spatial scales. Moreover, at small spatial scales it may enable pinpointing the source location of a sample to within at least 25 m, regardless of soil type and environmental conditions.     

Microbes in fingerprints: A source for dating crime evidence?

Interest in the human microbiome has grown in recent years because of increasing applications to biomedicine and forensic science. However, the potential for dating evidence at a crime scene based upon time-dependent changes in microbial signatures has not been established, despite a relatively straightforward scientific process for isolating the microbiome. We hypothesize that modifications in microbial diversity, abundance, and succession can provide estimates of the time a surface was touched for investigative purposes. In this proof-of-concept research, the sequencing and analysis of the 16 S rRNA gene from microbes present in fresh and aged latent fingerprints deposited by three donors with pre- and post-washed hands is reported. The stability of major microbial phyla is confirmed while the dynamics of less abundant groups is described up to 21 days post-deposition. Most importantly, a phylum is suggested as the source for possible biological markers to date fingerprints: Deinococcus-Thermus.     

Are antimicrobial peptides an alternative for conventional antibiotics?

Antimicrobial peptides are widespread in living organisms and constitute an important component of innate immunity to microbial infections. By the early 1980s, more than 800 different antimicrobial peptides had been isolated from mammals, amphibians, fish, insects, plants and bacterial species. In humans, they are produced by granulocytes, macrophages and most epithelial and endothelial cells. Newly discovered antibiotics have antibacterial, antifungal, antiviral and even antiprotozoal activity. Occasionally, a single antibiotic may have a very wide spectrum of activity and may show activity towards various kinds of microorganisms. Although antimicrobial activity is the most typical function of peptides, they are also characterized by numerous other properties. They stimulate the immune system, have anti-neoplastic properties and participate in cell signalling and proliferation regulation. As antimicrobial peptides from higher eukaryotes differ structurally from conventional antibiotics produced by bacteria and fungi, they offer novel templates for pharmaceutical compounds, which could be used effectively against the increasing number of resistant microbes.     

搭载后红曲霉菌突变株的染色体DNA随机扩增多态性分析研究

目的：研究太空诱变机理。方法：利用染色体DNA随机扩增多态性分析(RAPD)技术,对经“神舟”3号返回式飞船搭载的高产红曲霉菌进行DNA多态性分析。结果：突变株基因组DNA发生了改变。结论：突变株洛伐他汀产量的提高与其遗传基因的变异有关,太空诱变是通过改变搭载菌株的遗传基因而实现的。