Sticking to starch

Not all starches in the human diet are created equal: “resistant starches” are consolidated aggregates of the α-glucan polysaccharides amylose and amylopectin, which escape digestion by salivary and pancreatic amylases. Upon reaching the large intestine, resistant starches become fodder for members of the human gut microbiota, impacting the metabolism of both the symbionts and the host. In a recent study, Koropatkin et al. provided new molecular insight into how a keystone bacterium in the human gut microbiota adheres to resistant starches as a prelude to their breakdown and fermentation.     

高通量测序探究啮食聚苯乙烯泡沫塑料黄粉虫的肠道菌群结构

【目的】塑料废物处理是世界环境难题,近期有研究报道黄粉虫可啮食聚苯乙烯泡沫塑料,肠道细菌可能在黄粉虫生物降解塑料的过程中起重要作用。本文以啮食聚苯乙烯泡沫塑料的黄粉虫幼虫(Tenebrio molitor)为材料,探究其肠道细菌的多样性和细菌群落组成。【方法】分别以聚苯乙烯泡沫塑料(聚苯乙烯组)和纸片(对照组)为唯一食物来源喂养黄粉虫幼虫,在90 d后采集粪便样品,对16S r RNA基因V3-V4区进行PCR扩增和高通量测序,并以PICRUSt进行肠道菌群的功能预测。【结果】饲喂期间,两组黄粉虫均正常存活,部分幼虫完成变态发育。泡沫塑料有明显的减重。样本测序共得到144 258条有效序列,179个OTU,共涉及10个门111个属。其中,聚苯乙烯组黄粉虫的肠道细菌在属水平高丰度的是Alcaligenes(35.9%)、Brevundimonas(12.3%)、Myroides(10.3%)。基于16S r RNA基因序列的功能预测表明,在聚苯乙烯组中,芳香类化合物的降解基因被明显富集。【结论】高通量测序揭示了啮食聚苯乙烯泡沫塑料的黄粉虫肠道菌群的多样性,这对从黄粉虫肠道中分离高效降解聚苯乙烯的细菌具有指导意义。     

抗性淀粉对HFA小鼠肠道菌群的影响

目的 以人源菌群(HFA)小鼠为研究模型,观察抗性淀粉(RS)对高脂饮食诱导的肥胖小鼠肠道菌群的多样性的影响.方法 将30只无菌小鼠接种健康人志愿者的粪便悬液构建HFA小鼠模型后,随机分成3组,一组喂养含20％的抗性淀粉的高脂饲料(RS组),一组喂养纯高脂饲料(CK组),一组喂养普通饲料(CONV组),取第0周和第8周的小鼠新鲜粪便,用PCR-DGGE分析3组小鼠的肠道菌群的相似性和多样性.结果 3组小鼠在第0周时肠道菌群多样性的相似度达到79％～87％,与人的肠道菌群相似性达到39％,说明构建HFA小鼠模型成功,第8周时,3组之间的均匀度(E)和Shannon指数差异无统计学意义(P＞0.05),而丰富度(S)在高脂组(CK)与普通饲料组(CONV)和抗性淀粉组(RS)之间差异都有统计学意义(P＜0.05),说明高脂饮食引起肠道菌群多样性增加,而抗性淀粉则能降低这种多样性.结论 抗性淀粉可以显著影响HFA小鼠的肠道菌群多样性.     

植物附生微生物与叶部病害生物防治研究进展

人们早已发现绿色植物叶面(phylloplane)栖居有大量微生物。在一百多年前微生物学家就从植物叶面分离到许多真菌和细菌。1910年Potter首先证实,叶面附生微生物在干扰真菌引起的叶部病害中起着重要作用。至本世纪上半叶,叶面微生物仍为人们所忽视。相反,在这期间土壤微生物得到很大发展,在土传植物病原菌生物防治研究方法上取得了很大进展,为后来的植物叶部病害生物防     

Selection of bacteria originating from a human intestinal microbiota in the gut of previously germ-free rats

Denaturing gradient gel electrophoresis (DGGE) was applied to separate PCR-amplified 16S rRNA genes originating from human microbiota associated (HMA) rat faeces as well as from the human faecal sample used for inoculation of the animals. Subsequently, a total of 15 dominant bands were excised from the DGGE gels, cloned and sequenced. Comparison of the obtained sequences with the Ribosomal Database revealed that species of Bacteroides/Prevotella and Faecalibacterium gave rise to the majority of the dominant bands in the human sample and in the HMA rats. In the HMA rats, two dominant bands, which were not present in the human DGGE profile, originated from species of Ruminococcus. With the exception of the Ruminococcus sequences, sequences originating from both rats and human samples were represented in all major branches of a maximum parsimony tree, indicating that the rat feed and gut environment allows colonization of the dominant taxonomic units from the human microbiota, but additionally selects for Ruminococci. Bands representing Prevotella and Faecalibacterium, which were found in identical positions of the DGGE gels originating from human and HMA rat faecal samples, originated from completely identical sequences, indicating that the same strains of these species were dominating in the human and rat samples.     

Kinship,inbreeding and fine‐scale spatial structure influence gut microbiota in a hindgut‐fermenting tortoise

Herbivorous vertebrates rely on complex communities of mutualistic gut bacteria to facilitate the digestion of celluloses and hemicelluloses. Gut microbes are often convergent based on diet and gut morphology across a phylogenetically diverse group of mammals. However, little is known about microbial communities of herbivorous hindgut‐fermenting reptiles. Here, we investigate how factors at the individual level might constrain the composition of gut microbes in an obligate herbivorous reptile. Using multiplexed 16S rRNA gene sequencing, we characterized the faecal microbial community of a population of gopher tortoises (Gopherus polyphemus) and examined how age, genetic diversity, spatial structure and kinship influence differences among individuals. We recovered phylotypes associated with known cellulolytic function, including candidate phylum Termite Group 3, suggesting their importance for gopher tortoise digestion. Although host genetic structure did not explain variation in microbial composition and community structure, we found that fine‐scale spatial structure, inbreeding, degree of relatedness and possibly ontogeny shaped patterns of diversity in faecal microbiomes of gopher tortoises. Our findings corroborate widespread convergence of faecal‐associated microbes based on gut morphology and diet and demonstrate the role of spatial and demographic structure in driving differentiation of gut microbiota in natural populations.     

A comparison of nonlethal sampling methods for amphibian gut microbiome analyses

Noninvasive sampling methods for studying intestinal microbiomes are widely applied in studies of endangered species and in those conducting temporal monitoring during manipulative experiments. Although existing studies show that noninvasive sampling methods among different taxa vary in their accuracy, no studies have yet been published comparing nonlethal sampling methods in adult amphibians. In this study, we compare microbiomes from two noninvasive sample types (faeces and cloacal swabs) to that of the large intestine in adult cane toads, Rhinella marina. We use 16S rRNA gene sequencing to investigate how microbial communities change along the digestive tract and which nonlethal sampling method better represents large intestinal microbiota. We found that cane toads' intestinal microbiota was dominated by Bacteroidetes, Proteobacteria and Firmicutes and, interestingly, we also saw a high proportion of Fusobacteria, which has previously been associated with marine species and changes in frog immunity. The large and small intestine of cane toads had a similar microbial composition, but the large intestine showed higher diversity. Our results indicate that cloacal swabs were more similar to large intestine samples than were faecal samples, and small intestine samples were significantly different from both nonlethal sample types. Our study provides valuable information for future investigations of the cane toad gut microbiome and validates the use of cloacal swabs as a nonlethal method to study changes in the large intestine microbiome. These data provide insights for future studies requiring nonlethal sampling of amphibian gut microbiota.     

SCID小鼠肠道菌群失调对深部白色念珠菌感染的影响研究

目的建立重度联合免疫缺陷（SCID）小鼠白色念珠菌感染模型,探讨肠道菌群失调与深部白色念珠菌感染的联系。方法SCID小鼠随机口服万古霉素水溶液7d,饥饿24h后给予白色念珠菌灌胃,建立小鼠白色念珠菌感染模型,观察小鼠死亡情况。荧光定量PCR检测肠道细菌总量、基质辅助激光解析电离飞行时间质谱仪鉴定肠道菌群种类,并应用扫描电镜观察肠壁黏膜组织超微结构的改变。结果应用万古霉素可致肠道菌群失调,肠道黏膜完整性受损。在万古霉素致肠道菌群失调的基础上,外源性白色念珠菌攻击可加重肠道菌群失调和肠壁黏膜损伤程度,促进深部白色念珠菌感染的发生。结论肠道菌群失衡可以导致深部白色念珠菌感染的发生,肠壁黏膜的完整性可能参与了肠道白色念珠菌播散过程。     

SadA-Expressing Staphylococci in the Human Gut Show Increased Cell Adherence and Internalization

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