scholarly journals A core microbiota of the plant-earthworm interaction conserved across soils

2019 ◽  
Author(s):  
Samuel Jacquiod ◽  
Ruben Puga-Freitas ◽  
Aymé Spor ◽  
Arnaud Mounier ◽  
Cécile Monard ◽  
...  
Keyword(s):  
Microbial Communities ◽  
Bacterial Communities ◽  
Core Network ◽  
Core Microbiota ◽  
Soil Bacterial Communities ◽  
Community Theory ◽  
Source Sink ◽  
New Framework ◽  
Endogeic Earthworms

AbstractMicroorganisms participate in most crucial soil functions and services benefiting human activities, such as biogeochemical cycles, bioremediation and food production. Their activity happens essentially in hotspots created by major soil macroorganisms, like rhizosphere and cast shaped by plants and earthworms respectively1. While effects of individual macroorganism on soil microbes are documented, no studies attempted to decipher how the mosaic of microhabitats built by multiple macroorganisms and their interaction determine the structure of microbial communities. Here we show a joint shaping of soil bacterial communities by these two macroorganisms, with a prevalent role of plants over earthworms. In a controlled microcosm experiment with three contrasted soils and meticulous microhabitat sampling, we found that the simultaneous presence of barley and endogeic earthworms resulted in non-additive effects on cast and rhizosphere bacterial communities. Using a source-sink approach derived from the meta-community theory2,3, we found specific cast and rhizospherecore microbiota4,5of the plant-eartworm interaction, detected in all soils only when both macroorganisms are present. We also evidenced acore networkof the plant-earthworm interaction, with cosmopolitan OTUs correlated both in cast and rhizosphere of all soils. Our study provides a new framework to explore aboveground-belowground interactions through the prism of microbial communities. This multiple-macroorganisms shaping of bacterial communities also affects fungi and archaea, while being strongly influenced by soil type. Further functional investigations are needed to understand how thesecore microbiotaandcore networkcontribute to the modulation of plant adaptive response to local abiotic and biotic conditions.

scholarly journals Do soil bacterial communities respond differently to abrupt or gradual additions of copper?

2018 ◽  
Vol 95 (1) ◽  
Author(s):  
Michael McTee ◽  
Lorinda Bullington ◽  
Matthias C Rillig ◽  
Philip W Ramsey
Keyword(s):  
Heavy Metals ◽  
Soil Respiration ◽  
Microbial Communities ◽  
Bacterial Communities ◽  
Diversity Indices ◽  
Microbial Populations ◽  
Metal Concentrations ◽  
Soil Bacterial Communities ◽  
Bacterial Richness

ABSTRACTMany experiments that measure the response of microbial communities to heavy metals increase metal concentrations abruptly in the soil. However, it is unclear whether abrupt additions mimic the gradual and often long-term accumulation of these metals in the environment where microbial populations may adapt. In a greenhouse experiment that lasted 26 months, we tested whether bacterial communities and soil respiration differed between soils that received an abrupt or a gradual addition of copper or no copper at all. Bacterial richness and other diversity indices were consistently lower in the abrupt treatment compared to the ambient treatment that received no copper. The abrupt addition of copper yielded different initial bacterial communities than the gradual addition; however, these communities appeared to converge once copper concentrations were approximately equal. Soil respiration in the abrupt treatment was initially suppressed but recovered after four months. Afterwards, respiration in both the gradual and abrupt treatments wavered between being below or equal to the ambient treatment. Overall, our study indicates that gradual and abrupt additions of copper can yield similar bacterial communities and respiration, but these responses may drastically vary until copper concentrations are equal.

scholarly journals Neutral processes and high inter-annual turnover shape the assembly of soil bacterial communities in a Mediterranean watershed

2019 ◽  
Author(s):  
Myrto Tsiknia ◽  
Stilianos Fodelianakis ◽  
Nikolaos P. Nikolaidis ◽  
Nikolaos V. Paranychianakis
Keyword(s):  
Stochastic Processes ◽  
Microbial Communities ◽  
Bacterial Communities ◽  
Ecosystem Functioning ◽  
Soil Microbial Communities ◽  
Soil Bacterial Communities ◽  
Environmental Selection ◽  
Mediterranean Landscapes ◽  
Soil Bacterial ◽  
Annual Turnover

AbstractThere is a renewed interest in recent years on the ecological processes (stochastic vs selective) driving the assembly of microbial communities. Such information could potentially improve our understanding on ecosystem functioning and resilience to disturbances, ecosystem response to environmental shifts, and adoption of sustainable soil management practices. Herein, employing a suite of existing methodologies, we show that stochastic processes have an important role on the assembly of soil bacterial communities at a Mediterranean watershed. Moreover, we document that the relative contribution of assembly processes varies over the years. The observed intensification of stochastic processes was accompanied by a decrease in the contribution of variable selection in favor of homogeneous selection and dispersal and this trend was only marginally affected by land use (natural vs agricultural lands) or soil depth. Our study also revealed a high inter-annual turnover of soil microbial communities that was likely stimulated by the weak environmental selection and the prevailing environmental conditions (drying-wetting cycles) in Mediterranean landscapes, implying potential impacts on ecosystem functioning and our ability to predict soil response to environmental shifts. Using nitrogen mineralization rate (NMR) as a representative function we document highly variable NMR over the sampling years, land uses and soil depths and lack of significant associations with the monitored environmental variables and individual taxa. In summary, our study provides novel insights on the organization and functioning of microbial communities at Mediterranean ecosystems and sets directions towards a more advanced understanding of the relationships among environmental factors, microbial community structure, and ecosystem functioning that could contribute to sustainable management of these severely degraded ecosystems.

scholarly journals Impact of Land Use on Bacterial Diversity and Community Structure in Temperate Pine and Indigenous Forest Soils

Diversity ◽  
2019 ◽  
Vol 11 (11) ◽  
pp. 217 ◽  
Author(s):  
Adenike Eunice Amoo ◽  
Olubukola Oluranti Babalola
Keyword(s):  
Land Use ◽  
Microbial Communities ◽  
Bacterial Diversity ◽  
Correspondence Analysis ◽  
Canonical Correspondence Analysis ◽  
Bacterial Communities ◽  
Soil Microbial Communities ◽  
Soil Characteristics ◽  
Soil Bacterial Communities ◽  
Soil Bacterial

Soil microbial communities are an important part of ecosystems that possess the capability to improve ecosystem services; however, several aspects of the ecology of forest soil bacterial communities are still unknown. Here, we investigated the impact of land-use change on soil bacterial communities and the soil characteristics. High-throughput sequencing was used to ascertain the bacterial diversity and canonical correspondence analysis was used to determine relationships between the bacterial communities and environmental variables. Our results show spatial heterogeneity in the distribution of the microbial communities and significant relationships between the microbes and soil characteristics (axis 1 of the canonical correspondence analysis (CCA) plot explained 64.55% of the total variance while axis 2 described 24.49%). Knowledge of this is essential as it has direct consequences for the functioning of the soil ecosystem.

scholarly journals Host dietary specialization and neutral assembly shape gut bacterial communities of wild dragonflies

2018 ◽  
Author(s):  
Rittik Deb ◽  
Ashwin Nair ◽  
Deepa Agashe
Keyword(s):  
Bacterial Community ◽  
Microbial Communities ◽  
Host Species ◽  
Bacterial Communities ◽  
Gut Contents ◽  
Spatial And Temporal Variation ◽  
Dietary Specialization ◽  
Wild Host ◽  
Dragonfly Species

ABSTRACTHost-associated gut microbial communities can have large impacts on host ecology and evolution, and are typically shaped by host taxonomy and diet. Different host species often harbor distinct microbial communities, potentially because (1) host dietary specialization determines microbial colonization, (2) host-specific selection acts on diet-acquired microbiota, and (3) a combination of both processes. While the first possibility involves passive community structuring, the other two may arise from a functional association and should produce stable microbial communities. However, these alternatives have rarely been tested in wild host populations. We used 16S rRNA amplicon sequencing to characterize the gut bacterial communities of six dragonfly species collected across multiple seasons and locations. We found that variation in bacterial community composition was predominantly explained by sampling season and location, and secondarily by host species. To distinguish the role of host dietary specialization and host-imposed selection, we used insect-specific primers to identify prey in the gut contents of three focal dragonfly species. We found that these dragonflies – considered to be generalist predators – consumed distinct prey, with seasonal diet variation. Together, the patterns of host dietary specialization and spatial and temporal variation suggest a strong role of passive processes in shaping the gut bacterial community. Indeed, the abundance and distribution of ~76% of the bacterial community members were consistent with neutral community assembly. Our results contradict the pervasive expectation that host-imposed selection shapes gut microbial communities, and highlight the importance of joint analyses of variation in host diet and gut microbial communities of natural host populations.

scholarly journals A microcosm approach highlights the response of soil mineral weathering bacterial communities to an increase of K and Mg availability

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
O. Nicolitch ◽  
M. Feucherolles ◽  
J.-L. Churin ◽  
L. Fauchery ◽  
M.-P. Turpault ◽  
...  
Keyword(s):  
Bacterial Communities ◽  
Forest Ecosystems ◽  
Base Cations ◽  
Mineral Weathering ◽  
Taxonomic Structure ◽  
Soil Mineral ◽  
Soil Bacterial Communities ◽  
Amplicon Pyrosequencing ◽  
Pcr Targeting

Abstract The access and recycling of the base cations are essential processes for the long-lasting functioning of forest ecosystems. While the role of soil bacterial communities has been demonstrated in mineral weathering and tree nutrition, our understanding of the link between the availability of base cations and the functioning of these communities remains limited. To fill this gap, we developed a microcosm approach to investigate how an increase in key base cations (potassium or magnesium) impacted the taxonomic and functional structures of the bacterial communities. During a 2-month period after fertilization with available potassium or magnesium, soil properties, global functions (metabolic potentials and respiration) as well as mineral weathering bioassays and 16S rRNA amplicon pyrosequencing were monitored. Our analyses showed no or small variations in the taxonomic structure, total densities and global functions between the treatments. In contrast, a decrease in the frequency and effectiveness of mineral weathering bacteria was observed in the fertilized treatments. Notably, quantitative PCR targeting specific genera known for their mineral weathering ability (i.e., Burkholderia and Collimonas) confirmed this decrease. These new results suggest that K and Mg cation availability drives the distribution of the mineral weathering bacterial communities in forest soil.

scholarly journals Hand bacterial communities vary across two different human populations

Microbiology ◽  
2014 ◽  
Vol 160 (6) ◽  
pp. 1144-1152 ◽  
Author(s):  
Denina Hospodsky ◽  
Amy J. Pickering ◽  
Timothy R. Julian ◽  
Dana Miller ◽  
Sisira Gorthala ◽  
...  
Keyword(s):  
Microbial Communities ◽  
Bacterial Communities ◽  
Bacterial Population ◽  
Human Microbiome ◽  
Distinct Group ◽  
Human Populations ◽  
Skin Microbiome ◽  
Associated Bacteria ◽  
European Populations

This study utilized pyrosequencing-based phylogenetic library results to assess bacterial communities on the hands of women in Tanzania and compared these communities with bacteria assemblages on the hands of US women. Bacterial population profiles and phylogenetically based ordinate analysis demonstrated that the bacterial communities on hands were more similar for selected populations within a country than between the two countries considered. Organisms that have commonly been identified in prior human skin microbiome studies, including members of the Propionibacteriaceae, Staphylococcaceae and Streptococceacea families, were highly abundant on US hands and drove the clustering of US hand microbial communities into a distinct group. The most abundant bacterial taxa on Tanzanian hands were the soil-associated Rhodobacteraceae and Nocardioidaceae. These results help to expand human microbiome results beyond US and European populations, and the identification and abundance of soil-associated bacteria on Tanzanian hands demonstrated the important role of the environment in shaping the microbial communities on human hands.

scholarly journals Rapid Shifts in Bacterial Community Assembly under Static and Dynamic Hydration Conditions in Porous Media

2019 ◽  
Vol 86 (1) ◽  
Author(s):  
Hannah Kleyer ◽  
Robin Tecon ◽  
Dani Or
Keyword(s):  
Bacterial Community ◽  
Aqueous Phase ◽  
Community Assembly ◽  
Bacterial Communities ◽  
Critical Role ◽  
Abundant Species ◽  
Special Focus ◽  
Soil Bacterial Communities ◽  
Soil Bacterial

ABSTRACT The complexity of natural soils presents a challenge to the systematic identification and disentanglement of governing processes that shape natural bacterial communities. Studies have highlighted the critical role of the soil aqueous phase in shaping interactions among soil bacterial communities. To quantify and improve the attributability of soil aqueous-phase effects, we introduced a synthetic and traceable bacterial community to simple porous microcosms and subjected the community to constant or dynamic hydration conditions. The results were expressed in terms of absolute abundance and show species-specific responses to hydration and nutrient conditions. Hydration dynamics exerted a significant influence on the fraction of less-abundant species, especially after extended incubation periods. Phylogenetic relationships did not explain the group of most abundant species. The ability to quantify species-level dynamics in a bacterial community offers an important step toward deciphering the links between community composition and functions in dynamic terrestrial environments. IMPORTANCE The composition and activity of soil bacteria are central to various ecosystem services and soil biogeochemical cycles. A key factor for soil bacterial activity is soil hydration, which is in a constant state of change due to rainfall, drainage, plant water uptake, and evaporation. These dynamic changes in soil hydration state affect the structure and function of soil bacterial communities in complex ways often unobservable in natural soil. We designed an experimental system that retains the salient features of hydrated soil yet enables systematic evaluation of changes in a representative bacterial community in response to cycles of wetting and drying. The study shows that hydration cycles affect community abundance, yet most changes in composition occur with the less-abundant species (while the successful ones remain dominant). This research offers a new path for an improved understanding of bacterial community assembly in natural environments, including bacterial growth, maintenance, and death, with a special focus on the role of hydrological factors.

scholarly journals Floral organs act as environmental filters and interact with pollinators to structure the yellow monkeyflower (Mimulus guttatus) floral microbiome

2019 ◽  
Author(s):  
María Rebolleda Gómez ◽  
Tia-Lynn Ashman
Keyword(s):  
Microbial Communities ◽  
Bacterial Communities ◽  
Abiotic Factors ◽  
Geographic Distance ◽  
Mimulus Guttatus ◽  
Environmental Filters ◽  
Floral Organs ◽  
Environmental Selection ◽  
Plant Pollinator

AbstractAssembly of microbial communities is the result of neutral and selective processes. However, the relative importance of these processes is still debated. Microbial communities of flowers, in particular, have gained recent attention because of their potential impact to plant fitness and plant-pollinator interactions. However, the role of selection and dispersal in the assembly of these communities remains poorly understood. We evaluated the role of pollinator-mediated dispersal on the contribution of neutral and selective processes in the assembly of floral microbiomes of the yellow monkeyflower (Mimulus guttatus). We sampled floral organs from flowers in the presence and absence of pollinators within five different serpentine seeps in CA and obtained 16S amplicon data on the epiphytic bacterial communities. Consistent with strong micro-environment selection within flowers we observed significant differences in community composition across floral organs and only a small effect of geographic distance. Pollinator exposure affected the contribution of environmental selection and depended on the rate and “intimacy” of interactions with flower visitors. This study provides evidence of the importance of dispersal and within-flower heterogeneity in shaping epiphytic bacterial communities of flowers, and highlights the complex interplay between pollinator behavior, environmental selection and additional abiotic factors in shaping the epiphytic bacterial communities of flowers.

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