Causalities of war: The connection between type VI secretion system and microbiota

Microbiota niches have space and/or nutrient restrictions, which has led to the coevolution of cooperation, specialisation, and competition within the population. Different animal and environmental niches contain defined resident microbiota that tend to be stable over time and offer protection against undesired intruders. Yet fluxes can occur, which alter the composition of a bacterial population. In humans, the microbiota are now considered a key contributor to maintenance of health and homeostasis, and its alteration leads to dysbiosis. The bacterial type VI secretion system (T6SS) transports proteins into the environment, directly into host cells or can function as an antibacterial weapon by killing surrounding competitors. Upon contact with neighbouring cells, the T6SS fires, delivering a payload of effector proteins. In the absence of an immunity protein, this results in growth inhibition or death of prey leading to a competitive advantage for the attacker. It is becoming apparent that the T6SS has a role in modulating and shaping the microbiota at multiple levels, which is the focus of this review. Discussed here is the T6SS, its role in competition, key examples of its effect upon the microbiota, and future avenues of research.     

Intrinsically altered lung‐resident γδT cells control lung melanoma by producing interleukin‐17A in the elderly

Cancer is an age‐associated disease, potentially related to the altered immune system of elderly individuals. However, cancer has gradually decreased incidence in the eldest globally such as the most common lung cancer, the mechanisms of which remain to be elucidated. In this study, it was found that the number of lung‐resident γδT cells was significantly increased with altered gene expression in aged mice (20–24 months) versus young mice (10–16 weeks). Aged lung Vγ4⁺ and Vγ6⁺ γδT cells predominantly produced interleukin‐17A (IL‐17A), resulting in increased levels in the serum and lungs. Moreover, the aged mice exhibited smaller tumors and reduced numbers of tumor foci in the lungs after challenge with intravenous injection of B16/F10 melanoma cells compared with the young mice. Aged lung Vγ4⁺ and Vγ6⁺ γδT cells were highly cytotoxic to B16/F10 melanoma cells with higher expression levels of CD103. The markedly longer survival of the challenged aged mice was dependent on γδT17 cells, since neutralization of IL‐17A or depletion of indicated γδT cells significantly shortened the survival time. Consistently, supplementation of IL‐17A significantly enhanced the survival time of young mice with lung melanoma. Furthermore, the anti‐tumor activity of aged lung γδT17 cells was not affected by alterations in the load and composition of commensal microbiota, as demonstrated through co‐housing of the aged and young mice. Intrinsically altered lung γδT17 cells underlying age‐dependent changes control lung melanoma, which will help to better understand the lung cancer progression in the elderly and the potential use of γδT17 cells in anti‐tumor immunotherapy.     

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.     

鸡肠道微生物演替与早期定植的研究进展

鸡肠道中寄生着数量庞大且复杂多样的微生物,对宿主的生长发育和健康十分重要,既影响着饲料消化、营养物质吸收,又参与了宿主肠道形态和免疫系统的调控。深入了解鸡肠道微生物区系的时空变化及早期定植特点,将有助于提出新的肠道微生态干预策略,应用于生产。就鸡肠道微生物组成和演替、早期微生物区系建立及调控等方面进行综述,并总结了一些最新研究进展。     

孕妇肠道微生物组成与孕妇及新生儿糖脂代谢相关性研究

目的研究孕妇肠道微生物组成与孕妇以及新生儿糖脂代谢的相关性。方法选择2017年6月至2018年9月在大连市妇幼保健院定期产检的诊断为妊娠期糖尿病(GDM)的孕妇89例为GDM组,血糖正常孕妇96例为对照组。收集孕妇一般资料,孕妇和新生儿糖脂代谢物、孕妇粪便进行微生物检测。结果 GDM组孕妇空腹血糖、甘油三酯明显高于对照组,高密度脂蛋白水平明显低于对照组(均P<0.05)。GDM新生儿脂联素和血糖明显低于对照组,胰岛素和糖化血红蛋白明显高于对照组(均P<0.05)。对照组孕妇肠道微生物中拟杆菌(Bacteroides)丰富度最高(36.6%),其次是普雷沃菌(Prevotella)(15.3%)、柔嫩梭菌(Faecalibacterium)(10.2%)、考拉杆菌(Phascolarctobacterium)(7.2%)。GDM组孕妇肠道微生物中拟杆菌(Bacteroides)丰富度最高(29.4%),其次是柔嫩梭菌(Faecalibacterium)(19.7%)、普雷沃菌(Prevotella)(11.1%)、考拉杆菌(Phascolarctobacterium)(9.3%)。柔嫩梭菌(Faecalibacterium)与孕妇空腹血糖呈正相关(r=0.377 6,P=0.027 6),拟杆菌(Bacteroides)、埃希菌(Escherichia)与孕妇甘油三酯呈负相关(r=-0.027 5,-0.585 8,P=0.023 7,0.041 3)。柔嫩梭菌(Faecalibacterium)与新生儿空腹血糖呈负相关(r=-0.397 6,P=0.027 6)。结论 GDM孕妇肠道微生物构成与血糖正常孕妇不同,菌群丰富度和多样性较低,并且孕妇肠道菌群与其及新生儿的糖脂代谢相关,调节孕妇肠道菌群或有利于改善其与新生儿的糖脂代谢功能。     

利用宏基因组学方法分析健康人群肠道微生物与其生理指标的关系

目的探究亚洲健康人群的肠道菌群组成特征及其与血压和年龄相关生理指标的关系。方法应用WGCNA分析,对22个健康个体肠道微生物细菌基因组进行解析。结果亚洲健康人肠道微生物相对丰度最高的细菌门水平分别是Firmicutes(厚壁菌门)、 Bacteroidetes(拟杆菌门)以及Proteobacteria(变形菌门),并且在Proteobacteria中显示高差异性。WGCNA分析结果表明两个模块(yellow,green)中微生物物种丰富度分别与收缩压和舒张压以及年龄呈正相关(t=3.098 1,P=0.005 6;t=3.015 9,P=0.006 8;t=2.390 8,P=0.026 7)。其中Ruminococcus sp.(瘤胃球菌)、Oscillospiraceae sp.(颤螺菌)、Clostridium hathewayi(哈氏梭菌)与血压呈现显著正相关;Intestinibacter(肠杆菌)、Clostridium(梭菌)、Blautia(劳特菌)以及Veillonella(韦荣球菌)属下的Aypic、Tobetsuensis rogosae与年龄呈现正相关。抗性基因注释结果表明,年龄和血压相关核心菌群均富集有较多的大环内酯-林可酰胺-链霉素类、杆菌肽类以及四环素类抗生素抗性基因。其中多黏菌素类抗性基因仅存在于年龄相关核心菌群而氯霉素抗性基因仅存在于血压相关核心菌群。结论健康人肠道微生物物种丰度与血压以及年龄相关,肠道菌群可能在心血管疾病以及衰老过程中发挥重要影响。     

粪菌移植对非酒精性脂肪肝大鼠肠黏膜的保护作用

目的探讨粪菌移植(fecal microbiota transplantation,FMT)对非酒精性脂肪性肝病(nonalcoholic fatty liver disease,NAFLD)大鼠肠黏膜屏障的保护作用。方法健康雄性SD大鼠30只,随机分为3组:正常对照组(control group,C组)10只,予正常饮食;高脂模型组(model group,M组)10只、粪菌移植治疗组(treatment group,T组)10只,M组和T组均予高脂饮食。T组予粪菌液灌胃2 mL/次,隔日1次,粪菌液灌胃的前一天晚上及当天早上均予奥美拉唑镁肠溶片灌胃;C组及M组同时予奥美拉唑及生理盐水灌胃。喂养12周后实验结束,测定血中TG、ALT、AST水平;苏丹黑B染色观察肝脏病理学变化;取回肠末端肠组织行HE染色及扫描电镜观察肠黏膜结构变化。结果与M组大鼠相比,T组血清TG、ALT、AST水平降低,差异有统计学意义(均P0.05)。T组大鼠肝脏苏丹黑B染色可见肝细胞内脂肪沉积明显减少,脂肪变性程度较M组减轻。T组大鼠肠组织HE染色肠绒毛轻度水肿,排列较整齐、紧密。扫描电镜中可见T组大鼠肠绒毛形态较饱满,排列比较紧密,微绒毛之间的间隙变小。结论粪菌移植能改善肝功能,减轻肝脏脂肪变,降低肠道通透性,改善肠黏膜屏障功能。     

妊娠晚期阴道B族链球菌的感染对肠道菌群和妊娠结局的影响

目的探究妊娠晚期阴道B族链球菌(group B Streptococcus,GBS)的感染对肠道菌群和妊娠结局的影响。方法选取2018年3月至2019年11月大连市中心医院孕检并分娩的妊娠妇女744人为对象,调查并统计B族链球菌的感染率;筛选有和没有B族链球菌感染妊娠妇女各47人,调查不良妊娠结局的发生率;选取信息匹配的妊娠晚期阴道B族链球菌感染和未感染的妊娠妇女,采集粪便样本,提取菌群DNA,用16S rDNA方法分析菌群变化。结果744名妊娠妇女中B族链球菌检出49例,感染率为6.59%;B族链球菌感染组总的不良妊娠发生比例为76.6%,正常组发生比例为27.7%(χ^2=5.491,P<0.05)。B族链球菌感染组妊娠妇女胎膜早破(χ^2=16.177,P<0.01)、难产(χ^2=21.134,P<0.01)和羊水异常(χ^2=22.989,P<0.05)的发生率与未感染组比较显著增高。B族链球菌感染组妊娠妇女肠道菌群发生显著变化。结论妊娠晚期阴道B族链球菌的感染可能引起肠道菌群紊乱,增加不良妊娠结局。