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.

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 The role of plant‐pollinator interactions in structuring nectar microbial communities

2021 ◽  
Author(s):  
Clara de Vega ◽  
Sergio Álvarez‐Pérez ◽  
Rafael G. Albaladejo ◽  
Sandy‐Lynn Stennhuisen ◽  
Marc‐André Lachance ◽  
...  
Keyword(s):  
Microbial Communities ◽  
Plant Pollinator

scholarly journals Temporal and spatial changes in phyllosphere microbiome of acacia trees growing in arid environments

2020 ◽  
Author(s):  
Ashraf Al-Ashhab ◽  
Shiri Meshner ◽  
Rivka Alexander-Shani ◽  
Hana Dimerets ◽  
Michael Brandwein ◽  
...  
Keyword(s):  
Microbial Communities ◽  
Bacterial Diversity ◽  
16S Rdna ◽  
Air Temperature ◽  
Bacterial Communities ◽  
Abiotic Factors ◽  
Keystone Species ◽  
Arid Environments ◽  
Acacia Tortilis ◽  
Biotic Factor

Abstract Background: The evolutionary relationships between plants and their microbiome are of high importance to the survival of plants in extreme conditions. Changes in microbiome of plants can affect plant development, growth and health. Along the arid Arava, southern Israel, acacia trees ( Acacia raddiana and Acacia tortilis ) are considered keystone species. In this study, we investigated the ecological effects of plant species, microclimate (different areas within the tree canopies) and seasonality on the endophytic and epiphytic microbiome associated with these two tree species. 186 leaf samples were collected along different seasons throughout the year and their microbial communities were studied using the diversity of the 16S rDNA gene sequenced on the 150-PE Illumina sequencing platform. Results: our results showed amplifying V4 region of the 16S rDNA better presented the bacterial communities of both end and epiphytes of Acacia trees than V2, V3 and V5 regions of the 16S r DNA. When comparing the bacterial diversity of endo and epiphytes of the two acacia trees (shannon, choa1, PD and observed number of OTU’s), the epiphytes diversity indices showed about twice higher diversity compared to endophytes. The bacterial community compositions comparing both end and epiphytes were also significantly different. Interestingly, Acacia tortilis (umbral canopy shape) had a higher epiphytes bacterial diversity compared to Acacia raddiana, but were not statistically different. However the endophyte bacterial communities were significantly different compared to the two Acacia species (Firmicutes dominated Acacia raddiana and Proteobacteria dominated the Acacia tortilis ) . Alongside the biotic factor, Abiotic factors such as air temperature and precipitation also showed to significantly effect endo and epiphytes bacterial communities, while air humidity only affected the epiphytes bacterial communities.Conclusions: These results shed light on the unique desert phyllosphere microbiome in mitigating stress conditions highlighting the importance of epiphytic and endophytic microbial communities which are driven by different genotypic and abiotic factors. This paper also shows only a few bacteria species (OTUS’s) to dominate both epi and endophytes highlighting the importance of climate change (precipitation, Air temperature) in affecting arid land ecosystems where acacia trees are considered keystone species in many arid regions.

scholarly journals Temporal and spatial changes in phyllosphere microbiome of acacia trees growing in arid environments

2021 ◽  
Author(s):  
Ashraf Al-Ashhab ◽  
Shiri Meshner ◽  
Rivka Alexander-Shani ◽  
Hana Dimerets ◽  
Michael Brandwein ◽  
...  
Keyword(s):  
Microbial Communities ◽  
Bacterial Diversity ◽  
Air Temperature ◽  
Bacterial Communities ◽  
Abiotic Factors ◽  
Keystone Species ◽  
Tree Canopy ◽  
Arid Environments ◽  
Acacia Tortilis ◽  
Acacia Species

Abstract Background: The evolutionary relationships and interactions between plants and their microbiomes are of high importance to the survival of plants in extreme conditions. Changes in the plant’s microbiome can affect plant development, growth and health. Along the arid Arava, southern Israel, acacia trees (Acacia raddiana and Acacia tortilis) are considered keystone species. In this study, we investigated the ecological effects of plant species, microclimate (different areas within the tree canopy) and seasonality on the epiphytic and endophytic microbiomes associated with these two tree species. One hundred and thirty nine leaf samples were collected throughout the year and their microbial communities were assessed using 16S rDNA gene amplified with five different primers (targeting different gene regions) and sequenced (150 bp paired-end) on an Illumina MiSeq sequencing platform.Results: Epiphytic bacterial diversity estimates (Shannon-Wiener, Chao1, Simpson and observed number of OTUs), were found to be nearly double compared to endophyte counterparts, in addition epi- and endophyte communities were significantly different from each other. Interestingly, the epiphytic bacterial diversity was similar in the two acacia species but the canopy sides and sample months exhibited different diversity, while the endophytic bacterial communities were different in the two acacia species but similar throughout the year. Abiotic factors, such as air temperature and precipitation, were shown to significantly affect both epi- and endophytes communities. Bacterial community compositions showed that Firmicutes dominate Acacia raddiana and Proteobacteria dominate Acacia tortilis; these bacterial communities only consisted of a small number of bacterial families mainly Bacillaceae and Comamonadaceae in the endophyte for A. raddiana and A. tortilis, respectively, and Geodematophilaceae and Micrococcaceae for epiphyte bacterial communities. Interestingly, about 60% of the obtained bacterial classification were unclassified below family level. Conclusions: These results shed light on the unique desert phyllosphere microbiome highlighting the importance of multiple genotypic and abiotic factors in shaping the epiphytic and endophytic microbial communities. This study also shows that only a few bacterial families dominate both epi- and endophytes, highlighting the importance of climate change (precipitation, air temperature and humidity) in affecting arid land ecosystems where acacia trees are considered keystone species.

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 Environmental drivers define contrasting microbial habitats, diversity, and community structure in Lake Baikal, Siberia

2019 ◽  
Author(s):  
Paul Wilburn ◽  
Kirill Shchapov ◽  
Edward C. Theriot ◽  
Elena Litchman
Keyword(s):  
Community Structure ◽  
Microbial Communities ◽  
Lake Baikal ◽  
Mixed Layer ◽  
Abiotic Factors ◽  
Geographic Distance ◽  
Small World ◽  
Environmental Drivers ◽  
Ecosystem Responses ◽  
Baikal Water

ABSTRACTUnderstanding how microbial communities respond to environmental change requires knowing the main drivers of their structure, diversity and potential resilience. Lake Baikal is the world’s most ancient, deep, voluminous, and biodiverse lake, holding 20 percent of unfrozen fresh water that is undergoing rapid warming. Despite its global importance, little is known about Baikal’s bacterioplankton communities and their drivers. In this extensive survey, we show that temperature, along with stratification, nutrients, and dissolved oxygen, but not geographic distance, define major microbial habitats and community similarity. Mixed layer and deep water communities exhibited contrasting patterns of richness, diversity and evenness, and comprised different cohesive modules in the whole Baikal OTU co-occurrence network. The network’s small-world properties indicated likely resistance to perturbations but sensitivity to abundance changes of central, most connected OTUs. Previous studies showed Baikal water temperature rising by over 1.2°C since 1946, and this trend is predicted to accelerate. Because temperature emerged as the most significant predictor of the mixed layer community structure, we hypothesize that it is most likely to drive future community changes. Understanding how temperature and other abiotic factors structure microbial communities in this and other rapidly changing ecosystems will allow better predictions of ecosystem responses to anthropogenic stressors.

scholarly journals Structural, Metabolic and Evolutionary Comparison of Bacterial Endospore and Exospore Formation

2021 ◽  
Vol 12 ◽  
Author(s):  
Polina Beskrovnaya ◽  
Danielle L. Sexton ◽  
Mona Golmohammadzadeh ◽  
Ameena Hashimi ◽  
Elitza I. Tocheva
Keyword(s):  
Morphological Changes ◽  
Abiotic Factors ◽  
Bacterial Species ◽  
Genetic Material ◽  
Evolutionary Origins ◽  
Environmental Selection ◽  
Microbial Population Dynamics ◽  
Morphological Differences ◽  
Evolutionary Comparison

Sporulation is a specialized developmental program employed by a diverse set of bacteria which culminates in the formation of dormant cells displaying increased resilience to stressors. This represents a major survival strategy for bacteria facing harsh environmental conditions, including nutrient limitation, heat, desiccation, and exposure to antimicrobial compounds. Through dispersal to new environments via biotic or abiotic factors, sporulation provides a means for disseminating genetic material and promotes encounters with preferable environments thus promoting environmental selection. Several types of bacterial sporulation have been characterized, each involving numerous morphological changes regulated and performed by non-homologous pathways. Despite their likely independent evolutionary origins, all known modes of sporulation are typically triggered by limited nutrients and require extensive membrane and peptidoglycan remodeling. While distinct modes of sporulation have been observed in diverse species, two major types are at the forefront of understanding the role of sporulation in human health, and microbial population dynamics and survival. Here, we outline endospore and exospore formation by members of the phyla Firmicutes and Actinobacteria, respectively. Using recent advances in molecular and structural biology, we point to the regulatory, genetic, and morphological differences unique to endo- and exospore formation, discuss shared characteristics that contribute to the enhanced environmental survival of spores and, finally, cover the evolutionary aspects of sporulation that contribute to bacterial species diversification.

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.

Bacterial communities in shallow fractured-rock groundwater evolve over time, exhibiting cyclic patterns in response to multi-annual recharge events.

2021 ◽  
Author(s):  
Syrie Hermans ◽  
Lijuan Yan ◽  
Kai Uwe Totsche ◽  
Robert Lehmann ◽  
Martina Herrmann ◽  
...  
Keyword(s):  
Microbial Communities ◽  
Bacterial Communities ◽  
Fractured Rock ◽  
Sampling Period ◽  
Critical Zone ◽  
High Temporal Resolution ◽  
Rrna Gene ◽  
Environmental Selection ◽  
The Impact ◽  
Over Time

<p>Groundwater is an important component of the Earth’s critical zone and within this ecosystem, microbial communities play an important role, interacting with, and contributing to, the geology and hydrology of these systems; understanding how microbial communities in this dynamic zone change over time is therefore crucial. However, subsurface aquatic environments are lacking high-resolution temporal data over long time periods. Based on 16S rRNA gene sequences collected monthly over a six-year period (n=230) in groundwater from fractured Triassic limestone-mudstone alternations of the Hainich Critical Zone Exploratory (central Germany), we, therefore, aimed to disentangle the temporal dynamics of bacterial communities. The bacterial communities in the shallow bedrock groundwater showed multi-annual cyclic dissimilarity patterns which corresponded to groundwater level fluctuation and, thus, recharge discharge periods. The impact of groundwater fluctuation and linked cross-stratal exchange on the groundwater microbial communities was associated with the recharge strength and local environmental selection strength. Sampling period was able to explain up to 29.5% of the variability in bacterial community composition (based on a 2-factorial PERMANOVA model). We observed an increase in dissimilarity over time (Mantel P > 0.001) indicating that the successive recharge events result in bacterial communities that are increasingly more dissimilar to the communities at the start of the sampling period. Most bacteria in the groundwater originated from the recharge-related sources (mean = 66.5%, SD = 15.1%) and specific bacterial taxa were identified as being either enriched or repressed during recharge events. Overall, we show that seasonal recharge patterns are important for shaping bacterial communities in shallow fractured-rock groundwater and act as drivers of cyclical patterns. Furthermore, the recharge events are successive shocks that perturbed the bacterial communities, leading to decreased similarity to the original state over time. These revelations highlight the importance of high temporal resolution research in the Critical Zone for investigating the complex interplay between surface/subsurface environmental dynamics and the biology of groundwater ecosystems.</p>

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