Meiofauna promotes litter decomposition in stream ecosystems depending on leaf species

Litter decomposition, a fundamental process of nutrient cycling and energy flow in freshwater ecosystems, is driven by a diverse array of decomposers. As an important component of the heterotrophic food web, meiofauna can provide a trophic link between leaf‐associated microbes (i.e., bacteria and fungi)/plant detritus and macroinvertebrates, though their contribution to litter decomposition is not well understood. To investigate the role of different decomposer communities in litter decomposition, especially meiofauna, we compared the litter decomposition of three leaf species with different lignin to nitrogen ratios in litter bags with different mesh sizes (0.05, 0.25, and 2 mm) in a forested stream, in China for 78 days. The meiofauna significantly enhanced the decomposition of leaves of high‐and medium‐ quality, while decreasing (negative effect) or increasing (positive effect) the fungal biomass and diversity. Macrofauna and meiofauna together contributed to the decomposition of low‐quality leaf species. The presence of meiofauna and macrofauna triggered different aspects of the microbial community, with their effects on litter decomposition varying as a function of leaf quality. This study reveals that the meiofauna increased the trophic complexity and modulated their interactions with microbes, highlighting the important yet underestimated role of meiofauna in detritus‐based ecosystems.     

地被植物对广东常绿阔叶林土壤养分的指示作用

为了解地被植物群落对土壤养分的响应和指示作用,利用指示种分析(ISA)法研究了广东常绿阔叶林地被植物与土壤养分的关系。结果表明,速效氮(AN)、速效磷(AP)、速效钾(AK)和有机质(OM)的综合作用对地被植物分布有显著影响(P0.05),且以速效磷有机质速效钾速效氮。地被植物的组成与分布在不同AP和OM梯度中均有显著差异(P 0.05),但在不同AK和AN梯度中差异不显著。土壤AN≤270 mg/kg的指示种是广东蛇葡萄(Ampelopsis cantoniensis)和油点草(Tricyrtis macropoda),270～360 mg/kg的指示种是狗骨柴(Tricalysia dubia);AP≤2 mg/kg的指示种是华山姜(Alpinia chinensis);AK≤100mg/kg的指示种是赤楠蒲桃(Syzygiumbuxifolium),AK为100～150mg/kg的指示种是十字苔草(Carexcruciate),AK150 mg/kg的指示种是金钗凤尾蕨(Pterisfauriei);OM 0.8%的指示种是箬竹(Indocalamustessellatus),OM≤0.6%的指示种是华山姜(Alpinia chinensis)和蔓胡颓子(Elaeagnus glabra),OM为0.6%～0.8%的指示种是豆腐柴(Premna microphlla)。利用有效的地被植物调查方式来监测森林的土壤状况为森林经营管理及土壤健康评价带来方便。地被植物指示种对土壤养分的响应不但能为研究地的立地条件提供理论支撑,还能为该物种的人工栽培提供理论依据,这对于生物多样性保育、生境恢复的引种栽培有重要意义。     

三江源区生态系统和土壤保持服务对未来气候变化的响应特征

气候变化条件下的生态系统响应特征对生态系统服务的提升和生态环境保护具有重要意义。现有气候变化评估多以全球或区域大尺度研究为主,不适合局地小尺度。以2015年为基准,根据局地特征改进了综合顺序分类系统（CSCS）,模拟了未来不同温室气体排放模式下三江源地区自然植被分布,同时分析了植被覆盖度及土壤保持功能的时空变化。研究结果表明：①在2080年的不同排放情境下,三江源地区的降水和气温增长主要发生在生长季（5—9月）和半湿润地区,其中,高排放情境的增幅最大（42.21 mm和4.93℃）;②三江源地区潜在自然植被主要由草地转化为森林,植被覆盖度和土壤保持服务在不同排放情境下均呈现由西北向东南增加的趋势,与水热规律一致,其中高排放情境的增幅最大,低排放最小;③ 利用三江源地区原生裸地演替特点和多年NPP改进的CSCS模型,模拟精度提高了24%。研究成果为局地小尺度生态系统气候响应特征提供了必要的手段和规律认识。     

Evolution of specialized microbial cooperation in dynamic fluids

Here, we study the evolution of specialization using realistic computer simulations of bacteria that secrete two public goods in a dynamic fluid. Through this first‐principles approach, we find physical factors such as diffusion, flow patterns and decay rates are as influential as fitness economics in governing the evolution of community structure, to the extent that when mechanical factors are taken into account, (a) generalist communities can resist becoming specialists despite the invasion fitness of specialization; (b) generalist and specialists can both resist cheaters despite the invasion fitness of free‐riding; and (c) multiple community structures can coexist despite the opposing force of competitive exclusion. Our results emphasize the role of spatial assortment and physical forces on niche partitioning and the evolution of diverse community structures.     

基于Biolog-ECO方法的两种不同草原中5种不同植物根际土壤微生物群落特征

【背景】土壤微生物是草原生态系统的重要组成部分,在调节植物生长、促进土壤结构的形成及维持草原生态系统功能和稳定性等方面有着不可替代的作用。【目的】探究内蒙古自治区四子王旗两种不同草原中5种不同植物根际土壤微生物群落代谢功能的多样性。【方法】利用Biolog-ECO微平板法分析四子王旗荒漠草原中阿德格和格根塔拉2个样地中短花针茅、冷蒿、细叶葱、阿尔泰狗娃花和银灰旋花5种植物根际土壤微生物群落多样性特征。【结果】两种不同草原中5种不同植物根际土壤中可培养微生物数量存在显著性差异(P0.05),阿德格草原中短花针茅根际土壤中可培养微生物总数显著高于其他植物根际,格根塔拉草原中阿尔泰狗娃花根际土壤中可培养微生物总数显著高于其他植物;两样地不同植物根际土壤微生物的平均颜色变化率(average well color development,AWCD)均表现为格根塔拉样地高于阿德格样地,而且呈"S"型变化。培养96 h后格根塔拉草原5种植物的Shannon指数与Simpson指数高于阿德格草原,同时银灰旋花根际土壤微生物多样性指数在两个草原中差异极显著;两个草原不同植物根际土壤微生物对碳源的利用主要是氨基酸类和碳水化合物碳源,对于L-天门冬酰胺、r-羟基丁酸、L-丝氨酸和D-半乳糖醛酸等碳源的功能微生物显著富集,根际土壤微生物的AWCD和多样性指数与细菌、放线菌以及土壤微生物总数呈极显著正相关性(P0.01),均匀度指数与细菌、放线菌以及土壤微生物总数量呈显著负相关性(P0.05)。【结论】不同植物根际土壤微生物对碳源的利用能力和偏好出现差异,而且根际土壤微生物数量越高,微生物碳代谢能力、微生物群落多样性越丰富。     

肠道微生物对肠道屏障功能完整性的维护机制研究概况

肠道微生物群是一个稳定且复杂的生态系统,可以通过形成菌膜屏障或促进肠道上皮细胞增殖分化等方式形成保护屏障,并在肠道病原菌感染和威胁期间维持和促进免疫稳态中起积极作用。本文重点叙述宿主-肠道微生物相互作用过程中抗病原菌感染的方式,以及肠道微生物参与合成抗菌化合物抵御肠道病原菌入侵和威胁的机制,为调控肠道微生物解决临床胃肠道疾病及其相关症状提供理论参考依据。     

Comparative metabolomics implicates threitol as a fungal signal supporting colonization of Armillaria luteobubalina on eucalypt roots

Armillaria root rot is a fungal disease that affects a wide range of trees and crops around the world. Despite being a widespread disease, little is known about the plant molecular responses towards the pathogenic fungi at the early phase of their interaction. With recent research highlighting the vital roles of metabolites in plant root–microbe interactions, we sought to explore the presymbiotic metabolite responses of Eucalyptus grandis seedlings towards Armillaria luteobuablina, a necrotrophic pathogen native to Australia. Using a metabolite profiling approach, we have identified threitol as one of the key metabolite responses in E. grandis root tips specific to A. luteobubalina that were not induced by three other species of soil-borne microbes of different lifestyle strategies (a mutualist, a commensalist, and a hemi-biotrophic pathogen). Using isotope labelling, threitol detected in the Armillaria-treated root tips was found to be largely derived from the fungal pathogen. Exogenous application of d- threitol promoted microbial colonization of E. grandis and triggered hormonal responses in root cells. Together, our results support a role of threitol as an important metabolite signal during eucalypt-Armillaria interaction prior to infection thus advancing our mechanistic understanding on the earliest stage of Armillaria disease development. Comparative metabolomics of eucalypt roots interacting with a range of fungal lifestyles identified threitol enrichment as a specific characteristic of Armillaria pathogenesis. Our findings suggest that threitol acts as one of the earliest fungal signals promoting Armillaria colonization of roots.     

聚乙烯塑料的微生物降解

聚乙烯(polyethylene,PE)是产量最大的通用塑料之一,通常被加工成一次性包装材料(包括塑料袋及容器)和农用薄膜等。PE塑料的广泛应用导致大量PE废弃物的累积,对生态环境造成严重的威胁。自20世纪70年代以来,一些研究陆续报道了PE塑料被微生物降解的现象,并从土壤、海洋、垃圾堆置点及昆虫肠道等生境中分离筛选到了若干种具有一定PE塑料降解能力的菌株,而且发现一些单加氧酶、过氧化物酶和漆酶等氧化还原酶对PE塑料具有氧化降解能力。这些研究为发展PE塑料废弃物生物降解处理技术提供了一定的依据。本文总结和分析了PE塑料降解微生物的分离和筛选方法,以及已报道的PE塑料降解微生物和降解酶的研究进展,以期为进一步研究PE塑料的微生物降解机理和处理技术提供参考。     

Microbes make the meal: oligolectic bees require microbes within their host pollen to thrive

1. For solitary bees that specialise on select pollen types (oligoleges), larval development depends on the availability of forage pollen from appropriate host plants and the naturally occurring microbiota present therein. While access to host pollen may be critical for the development of oligolectic bees, the extent to which pollen microbiota contribute to their brood success is unknown. 2. To investigate, we used a diet manipulation experiment to rear larvae of the oligolege, Osmia ribifloris, under in-vitro conditions. Larvae were reared either on host pollen provisioned by their mother or on non-host pollen collected by honey bees, in the presence or absence of the respective pollen-associated microbiota. We assessed impacts on components of larval fitness: developmental time, biomass, and survivorship. 3. Our results revealed a significant interaction between pollen type and pollen-associated microbes. The relative effect of microbes on larval performance was substantially greater than that of pollen type. Host pollen substrate produced the fittest larvae but only when combined with its full complement of naturally occurring microbiota. In contrast, host pollen without microbes resulted in a marked decline in fitness components. Larvae consuming non-host pollen showed intermediate fitness, regardless of whether microbes were present or not. 4. These findings imply that the microbiota associated with maternally provisioned host pollen perform critical functions in larval nutrition and survival. For oligoleges in particular, the ability to develop on poorer quality host pollen likely derives from this sustained symbiosis with their microbial exosymbionts, rather than the biochemical characteristics of pollen type alone.     

Distribution and bioaccumulation of trace elements and lanthanides in apples from Northwestern Italy

BackgroundTransfer of metals from soil to plant is a possible route of contamination for the food chain. This investigation focused on the occurrence of 40 elements in the “Red Apple of Cuneo”, an Italian excellence and a Protected Geographical Indication (P.G.I.). Four cultivars were considered: Red Delicious (Jeromine) and Gala (Bukeye, Brookfield, Schniga).MethodsTrace elements and rare earth elements (REEs) detection was performed by an Inductively Coupled Plasma-Mass Spectrometer (ICP-MS) previous homogenization of samples and microwave acid digestion. One-way analysis of variance (ANOVA) with Bonferroni correction was employed to for statistical analysis.ResultsConcentrations of metals in the four apples cultivars were quite comparable, Al and Rb were the most represented nonessential elements while Fe, Cu and Zn between the essential; REEs were found at negligible concentrations. Bioaccumulation factors demonstrated an extremely low capacity of bioaccumulation from soil to fruit.ConclusionsThe analysis performed on the “Red Apple of Cuneo” has shown that this product is safe for human consumption since metals were recovered at concentrations of no concern and lower than those registered in apples from other countries.Since each production area is characterized by a typical elemental pattern the multielemental profile based on the analysis of 40 elements could be useful to relate products to their region of origin. Differences between the four apple cultivars were instead not significant to discriminate between them.