scholarly journals Stochastic microbial community assembly decreases biogeochemical function

2017 ◽  
Author(s):  
Emily B. Graham ◽  
James C. Stegen
Keyword(s):  
Microbial Communities ◽  
Local Community ◽  
Niche Breadth ◽  
Relative Influence ◽  
Ecological Simulation ◽  
Ecological Mechanisms ◽  
Community Fitness ◽  
Specialist Species ◽  
Microbial Community Assembly ◽  
Different Levels

AbstractEcological mechanisms influence relationships among microbial communities, which in turn impact biogeochemistry. In particular, microbial communities are assembled by deterministic (e.g., selection) and stochastic (e.g., dispersal) processes, and the relative influence of these two process types is hypothesized to alter the influence of microbial communities over biogeochemical function, which we define generically to represent any biogeochemical reaction of interest. We used an ecological simulation model to evaluate this hypothesis. We assembled receiving communities under different levels of dispersal from a source community that was assembled purely by deterministic selection. The dispersal scenarios ranged from no dispersal (i.e., selection-only) to dispersal rates high enough to overwhelm selection (i.e., homogenizing dispersal). We used an aggregate measure of community fitness to infer its biogeochemical function relative to other communities. We also used ecological null models to further link the relative influence of deterministic assembly to function. We found that increasing rates of dispersal decrease biogeochemical function by increasing the proportion of maladapted taxa in a local community. Niche breadth was also a key determinant of biogeochemical function, suggesting a tradeoff between the function of generalist and specialist species. Together, our results highlight the influence of spatial processes on biogeochemical function and indicate the need to account for such effects in models that aim to predict biogeochemical function under future environmental scenarios.

scholarly journals Deterministic Selection Dominates Microbial Community Assembly in Termite Mounds Across a Large Spatial Area

2020 ◽  
Author(s):  
Qing-Lin Chen ◽  
Hang-Wei Hu ◽  
Zhen-Zhen Yan ◽  
Chao-Yu Li ◽  
Bao-Anh Thi Nguyen ◽  
...  
Keyword(s):  
Microbial Community ◽  
Stochastic Processes ◽  
Microbial Communities ◽  
Fungal Community ◽  
Community Assembly ◽  
Distance Decay ◽  
Termite Mounds ◽  
Deterministic Processes ◽  
Microbial Community Assembly

Abstract Background: Termites are ubiquitous insects in tropical and subtropical habitats, where they construct massive mounds from soil, their saliva and excreta. Termite mounds harbor an enormous amount of microbial inhabitants, which regulate multiple ecosystem functions such as mitigating methane emissions and increasing ecosystem resistance to climate change. However, we lack a mechanistic understanding about the role of termite mounds in modulating the microbial community assembly processes, which are essential to unravel the biological interactions of soil fauna and microorganisms, the major components of soil food webs. We conducted a large-scale survey across a >1500 km transect in northern Australia to investigate biogeographical patterns of bacterial and fungal community in 134 termite mounds and the relative importance of deterministic versus stochastic processes in microbial community assembly. Results: Microbial alpha (number of phylotypes) and beta (changes in bacterial and fungal community composition) significantly differed between termite mounds and surrounding soils. Microbial communities in termite mounds exhibited a significant distance-decay pattern, and fungal communities had a stronger distance-decay relationship (slope = -1.91) than bacteria (slope = -0.21). Based on the neutral community model (fitness < 0.7) and normalized stochasticity ratio index (NST) with a value below the 50% boundary point, deterministic selection, rather than stochastic forces, predominated the microbial community assembly in termite mounds. Deterministic processes exhibited significantly weaker impacts on bacteria (NST = 45.23%) than on fungi (NST = 33.72%), probably due to the wider habitat niche breadth and higher potential migration rate of bacteria. The abundance of antibiotic resistance genes (ARGs) was negatively correlated with bacterial/fungal biomass ratios, indicating that ARG content might be an important biotic factor that drove the biogeographic pattern of microbial communities in termite mounds. Conclusions: Deterministic processes play a more important role than stochastic processes in shaping the microbial community assembly in termite mounds, an unique habitat ubiquitously distributed in tropical and subtropical ecosystems. An improved understanding of the biogeographic patterns of microorganisms in termite mounds is crucial to decipher the role of soil faunal activities in shaping microbial community assembly, with implications for their mediated ecosystems functions and services.

scholarly journals Agricultural constraints on microbial resource use and niche breadth in drainage ditches

2017 ◽  
Author(s):  
Ellard R Hunting ◽  
Henrik Barmentlo ◽  
Maarten Schrama ◽  
Peter van Bodegom ◽  
Yujia Zhai ◽  
...  
Keyword(s):  
Organic Matter ◽  
Microbial Communities ◽  
Resource Utilization ◽  
Agricultural Land ◽  
Niche Breadth ◽  
Niche Differentiation ◽  
Drainage Ditches ◽  
Substrate Quality ◽  
Degradation Rates ◽  
Natural Communities

Background. Microorganisms govern important ecosystems processes, in particular the degradation of organic matter (OM). However, microorganisms are rarely considered in efforts to monitor ecosystem health and functioning. Evidence suggests that environmental perturbations can adversely affect microbial communities and and their ability to use available substrates. However, whether impacted microbial efficiencies in extracting and utilizing the available resources (resource niche breadth) translate to changes in organic matter (OM) degradation in natural systems remains poorly understood. Methods. Here we evaluated effects of differences in organic matter (OM) related to agricultural land use (OM derived from ditches adjacent to grasslands, bulb fields and a pristine dune area) on microbial functioning. We specifically assessed 1) resource niche breadths of microbial communities during initial community assembly in laboratory microcosms and already established natural communities, and 2) how changes in community resource niche breadth translates to the degradation of natural OM. Results. A disparity existed between microbial resource niche breadth in laboratory incubations and natural microbial communities. Resource utilization and niche breadth of natural microbial communities was observed to be constrained in drainage ditches adjacent to agricultural fields. This outcome coincides with retarded degradation of natural OM collected from ditches adjacent to hyacinth bulb fields. Microbial communities in bulb field ditches further showed functional redundancy when offered grassland OM of seemingly higher substrate quality. Discussion. Results presented in this study suggest that agricultural practices can impose constraints on microbial functional diversity by reducing OM resource quality, which can subsequently translate to confined microbial resource niche differentiation and reduced organic matter degradation rates. This hints that assessments of actual microbial resource utilization and niche differentiation could potentially be used to assess the ecological health and functioning of natural communities.

scholarly journals Hill-based Dissimilarity Indices and Null Models for Analysis of Microbial Community Assembly

2020 ◽  
Author(s):  
Oskar Modin ◽  
Raquel Liebana ◽  
Soroush Saheb-Alam ◽  
Britt-Marie Wilén ◽  
Carolina Suarez ◽  
...  
Keyword(s):  
Microbial Community ◽  
Microbial Communities ◽  
Community Assembly ◽  
Null Model ◽  
Amplicon Sequencing ◽  
Null Models ◽  
Marker Genes ◽  
Experimental Systems ◽  
Microbial Community Assembly ◽  
The Impact

Abstract Background: High-throughput amplicon sequencing of marker genes, such as the 16S rRNA gene in Bacteria and Archaea, provides a wealth of information about the composition of microbial communities. To quantify differences between samples and draw conclusions about factors affecting community assembly, dissimilarity indices are typically used. However, results are subject to several biases and data interpretation can be challenging. The Jaccard and Bray-Curtis indices, which are often used to quantify taxonomic dissimilarity, are not necessarily the most logical choices. Instead, we argue that Hill-based indices, which make it possible to systematically investigate the impact of relative abundance on dissimilarity, should be used for robust analysis of data. In combination with a null model, mechanisms of microbial community assembly can be analyzed. Here, we also introduce a new software, qdiv, which enables rapid calculations of Hill-based dissimilarity indices in combination with null models.Results: Using amplicon sequencing data from two experimental systems, aerobic granular sludge (AGS) reactors and microbial fuel cells (MFC), we show that the choice of dissimilarity index can have considerable impact on results and conclusions. High dissimilarity between replicates because of random sampling effects make incidence-based indices less suited for identifying differences between groups of samples. Determining a consensus table based on count tables generated with different bioinformatic pipelines reduced the number of low-abundant, potentially spurious amplicon sequence variants (ASVs) in the data sets, which led to lower dissimilarity between replicates. Analysis with a combination of Hill-based indices and a null model allowed us to show that different ecological mechanisms acted on different fractions of the microbial communities in the experimental systems.Conclusions: Hill-based indices provide a rational framework for analysis of dissimilarity between microbial community samples. In combination with a null model, the effects of deterministic and stochastic community assembly factors on taxa of different relative abundances can be systematically investigated. Calculations of Hill-based dissimilarity indices in combination with a null model can be done in qdiv, which is freely available as a Python package (https://github.com/omvatten/qdiv). In qdiv, a consensus table can also be determined from several count tables generated with different bioinformatic pipelines.

scholarly journals Initial tasks

2019 ◽  
pp. 70-85
Author(s):  
Ted Lankester
Keyword(s):  
Local Community ◽  
House Staff ◽  
Team Members ◽  
Health Team ◽  
External Sources ◽  
Project Cycle ◽  
Set Up ◽  
And Training ◽  
Different Levels ◽  
Health Programme

This chapter explores how the community and the health programme can work together in selecting and training appropriate health team members at different levels of expertise. It identifies situations that require caution and understanding, and describes the project cycle. It outlines how to set up a project base, house staff, and identify security needs. It describes options for transport, how transport may be perceived by the local community, and includes questions that should be asked when considering buying a vehicle. It describes methods for ordering supplies, equipment vital to the project, and medicines that should be considered. Finally, it gives a range of ideas on how to fund a project, both from internal and external sources, and provides examples of each.

scholarly journals Cohesiveness in microbial community coalescence

2018 ◽  
Author(s):  
Nanxi Lu ◽  
Alicia Sanchez-Gorostiaga ◽  
Mikhail Tikhonov ◽  
Alvaro Sanchez
Keyword(s):  
Microbial Community ◽  
Microbial Communities ◽  
Empirical Work ◽  
Invasion Success ◽  
Community Members ◽  
Interacting Species ◽  
Resource Interactions ◽  
Different Origins ◽  
Microbial Community Assembly ◽  
Selection Of

AbstractMicrobial invasions exhibit many unique properties; notably, entire microbial communities often invade one another, a phenomenon known as community coalescence. In spite of the potential importance of this process for the dynamics and stability of microbiome assembly, our understanding of it is still very limited. Recent theoretical and empirical work has proposed that large microbial communities may exhibit an emergent cohesiveness, as a result of collective consumer-resource interactions and metabolic feedbacks between microbial growth and the environment. A fundamental prediction of this proposal is the presence of ecological co-selection during community coalescence, where the invasion success of a given taxon is determined by its community members. To establish the generality of this prediction in experimental microbiomes, we have performed over one hundred invasion and coalescence experiments with environmental communities of different origins that had spontaneously and stably assembled in two different synthetic aerobic environments. We show that the dominant species of the coalesced communities can both recruit their community members (top-down co-selection) and be recruited by them (bottom-up co-selection) into the coalesced communities. Our results provide direct evidence that collective invasions generically produce ecological co-selection of interacting species, emphasizing the importance of community-level interactions during microbial community assembly.

scholarly journals A conceptual framework for the phylogenetically constrained assembly of microbial communities

Microbiome ◽  
2019 ◽  
Vol 7 (1) ◽  
Author(s):  
Daniel Aguirre de Cárcer
Keyword(s):  
Microbial Community ◽  
Microbial Communities ◽  
Community Assembly ◽  
Phylogenetic Signal ◽  
A Priori ◽  
Amplicon Sequencing ◽  
Bioinformatic Analysis ◽  
Microbial Ecosystems ◽  
And Function ◽  
Microbial Community Assembly

Abstract Microbial communities play essential and preponderant roles in all ecosystems. Understanding the rules that govern microbial community assembly will have a major impact on our ability to manage microbial ecosystems, positively impacting, for instance, human health and agriculture. Here, I present a phylogenetically constrained community assembly principle grounded on the well-supported facts that deterministic processes have a significant impact on microbial community assembly, that microbial communities show significant phylogenetic signal, and that microbial traits and ecological coherence are, to some extent, phylogenetically conserved. From these facts, I derive a few predictions which form the basis of the framework. Chief among them is the existence, within most microbial ecosystems, of phylogenetic core groups (PCGs), defined as discrete portions of the phylogeny of varying depth present in all instances of the given ecosystem, and related to specific niches whose occupancy requires a specific phylogenetically conserved set of traits. The predictions are supported by the recent literature, as well as by dedicated analyses. Integrating the effect of ecosystem patchiness, microbial social interactions, and scale sampling pitfalls takes us to a comprehensive community assembly model that recapitulates the characteristics most commonly observed in microbial communities. PCGs’ identification is relatively straightforward using high-throughput 16S amplicon sequencing, and subsequent bioinformatic analysis of their phylogeny, estimated core pan-genome, and intra-group co-occurrence should provide valuable information on their ecophysiology and niche characteristics. Such a priori information for a significant portion of the community could be used to prime complementing analyses, boosting their usefulness. Thus, the use of the proposed framework could represent a leap forward in our understanding of microbial community assembly and function.

scholarly journals Households and communities in the central Anatolian Neolithic

2005 ◽  
Vol 12 (2) ◽  
pp. 165-187 ◽  
Author(s):  
Bleda S. Düring ◽  
Arkadiusz Marciniak
Keyword(s):  
Local Community ◽  
Basic Component ◽  
Central Anatolia ◽  
Multiple Forms ◽  
Domestic Activities ◽  
Social Associations ◽  
Different Levels ◽  
Over Time ◽  
Social Association

The neolithic communities of central Anatolia are generally reconstructed as being constituted by relatively autonomous and homologous households occupying discrete residences and performing most domestic activities in the house. In this reconstruction households are seen as the uniform and unproblematic basic component of society. This paper aims to problematize this modular conception of central Anatolian Neolithic societies, and wants to draw attention to the multiple forms in which households occurred and the manner in which they were embedded in larger social associations. It is argued that different levels of social association can only be understood in relation to each other. Further, the manner in which social configurations in central Anatolia changed over time is explored. This will be done by presenting evidence from two central Anatolian Neolithic sites: Aşıklı Höyük and Çatalhöyük. In particular, we argue that households became autonomous and clearly bounded entities only towards the end of the central Anatolian Neolithic, and that too little consideration has been given to the neighbourhood and the local community encompassing individual households.

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