Biology subjects

Bittleston, L. S.

Publications and source records attributed to Bittleston, L. S..

6 recordsLinked to original sources

bioRxiv2025

Context-dependent effects of microbial inoculation on sagebrush seedlings during drought stress

The leaf microbiome interacts with its plant host and can have critical positive and negative effects on plant health. However, the interactions between leaf microbiomes and host plants remain understudied, particularly in reference to context-dependency, e.g., during drought conditions. Plants naturally exist in environments with ever-changing weather and epiphytic foliar microbes are often exposed to extreme conditions. Little is known about how different environmental contexts can alter the effects of phyllosphere microbes on their plant hosts. In this study, we measured the response of seedlings to microbial inoculations and drought conditions. We used Artemisia tridentata subsp. tridentata (hereafter, sagebrush), a foundation species in the vast and critically threatened sagebrush steppe ecosystem. We grew sagebrush plants in growth chambers from sterile seed and after 6 months the seedlings were inoculated in one of four inoculation treatments: (1) no inoculant, (2) sterile water, (3) the microbes washed from the surface of the leaves (a whole natural community), and (4) the single species, Bacillus amyloliquefaciens. We then exposed the seedlings to two environmental treatments: regular watering and a tapered drought. We found context-dependent effects of inoculation on seedling health for both of our inoculation microbial treatments. For example, both inoculants had a negative effect on host plant photosynthesis, which was lessened drought conditions. Furthermore, seedlings inoculated with B. amyloliquefaciens had increased leaf nitrogen levels, and the highest survival under drought conditions. Our study shows that seedling health and survival can be influenced by leaf-associated microbes, and is dependent on environmental context.

plant biology↗

bioRxiv2024

Weather and leaf age separately contribute to temporal shifts in phyllosphere community structure and composition

Microbial communities living on plant leaves can positively or negatively influence plant health and, by extension, can impact whole ecosystems. Most research into the leaf microbiome consists of snapshots, and little is known about how microbial communities change over time. Weather and host physiological characteristics change over time and are often collinear with other time-varying factors, such as substrate availability, making it difficult to separate the factors driving microbial community change. We leveraged repeated measures over the course of an entire year to isolate the relative importance of environmental, host physiological, and substrate age-related factors on the assembly, structure, and composition of leaf-associated fungal communities. We applied both culturing and sequencing approaches to investigate these communities, focusing on a foundational, widely-distributed plant of conservation concern: basin big sagebrush (Artemisia tridentata subsp. tridentata). We found that changes in alpha diversity were independently affected by the age of a community and the air temperature. Surprisingly, total fungal abundance and species richness were not positively correlated and responded differently, sometimes oppositely, to weather. With regard to beta diversity, communities were more similar to each other across similar leaf ages, air temperatures, leaf types, and {delta}13C stable isotope ratios. Nine different genera were differentially abundant with air temperature, {delta}13C, leaf type, and leaf age, and a set of 20 genera were continuously present across the year. Our findings highlight the necessity for longer-term, repeated sampling to parse drivers of temporal change in leaf microbial communities. Open Research StatementAll ITS DNA amplicon sequence raw data are deposited in the NCBI Sequence Read Archive (SRA), BioProject number PRJNA1107252, data will be released upon publication. All community data, metadata, taxonomic data, and R code necessary to reproduce these results are deposited in the GitHub repository archived on Zenodo: 10.5281/zenodo.11106439.

ecology↗

bioRxiv2024

Microbial community function increases host plant leaf growth in a pitcher plant experimental system

Across diverse ecosystems, bacteria and their host organisms engage in complex relationships having negative, neutral, or positive interactions. However, the specific effects of leaf- associated bacterial community functions on plant growth are poorly understood. To address this gap, we explored the relationships between bacterial community function and host plant growth in the purple pitcher plant (Sarracenia purpurea). The main aim of our research was to investigate how different bacterial community functions affect the growth and nutrient content in the plant. Previous research had suggested that microbial communities may aid in prey decomposition and subsequent nutrient acquisition in carnivorous plants, including S. purpurea. However, the specific functional roles of these bacterial communities in plant growth and nutrient uptake are not well known. In this study, sterile, freshly opened leaves (pitchers) were inoculated with three functionally distinct, pre-assembled bacterial communities and effects examined over 8 weeks. Bacterial community composition and function were measured using physiological assays, metagenomics, and metatranscriptomics. Distinct bacterial functions affected plant traits; a bacterial community enriched in decomposition and secondary metabolite production traits was associated with larger leaves with almost double the biomass of control pitchers. Physiological differences in bacterial communities were supported by metatranscriptomic analysis; for example, the bacterial community with the highest chitinase activity had greater expression of transcripts associated with chitinase enzymes. The relationship between bacterial community function and plant growth observed here indicates potential mechanisms for host-associated bacterial functions to support plant health and growth. ImportanceThis study addresses a gap in understanding the relationships between bacterial community function and plant growth. We inoculated sterile, freshly opened pitcher plant leaves with three functionally distinct bacterial communities to uncover potential mechanisms through which bacterial functions support plant health and growth. Our findings demonstrate that distinct bacterial functions significantly influence plant traits, with some bacterial communities supporting more growth than in control pitchers. These results highlight the ecological roles of microbial communities in plants and thus ecosystems, and suggest potential pathways in which microbes support host plant health. This research provides valuable insights into plant-microbe interactions and effects of diverse microbial community functions.

ecology↗

bioRxiv2021

Interactions between strains govern the eco-evolutionary dynamics of microbial communities

Genomic data has revealed that genotypic variants of the same species, i.e., strains, coexist and are abundant in natural microbial communities. However, it is not clear if strains are ecologically equivalent, or if they exhibit distinct interactions and dynamics. Here, we address this problem by tracking 10 microbial communities from the pitcher plant Sarracenia purpurea in the laboratory for more than 300 generations. Using metagenomic sequencing, we reconstruct their dynamics over time and across scales, from distant phyla to closely related genotypes. We find that interactions between naturally occurring strains govern eco-evolutionary dynamics. Surprisingly, even fine-scale variants differing only by 100 base pairs can exhibit vastly different dynamics. We show that these differences may stem from ecological interactions in the communities, which are specific to strains, not species. Finally, by analyzing genomic differences between strains, we identify major functional hubs such as transporters, regulators, and carbohydrate-catabolizing enzymes, which might be the basis for strain-specific interactions. Our work shows that strains are the relevant level of diversity at which to study the long-term dynamics of microbiomes.

microbiology↗

bioRxiv2019

Quantifying the relative importance of competition, predation, and environmental variation for species coexistence

1Coexistence theory and food web theory are two cornerstones of the longstanding effort to understand how species coexist. Although competition and predation are known to act simultaneously in communities, theory and empirical study of the two processes continue to be developed independently. Here, we integrate modern coexistence theory and food web theory to simultaneously quantify the relative importance of predation, competition, and environmental fluctuations for species coexistence. We first examine coexistence in a classic multi-trophic model, adding complexity to the food web using a novel machine learning approach. We then apply our framework to a parameterized rocky intertidal food web model, partitioning empirical coexistence dynamics. We find that both environmental fluctuation and variation in predation contribute substantially to species coexistence. Unexpectedly, covariation in these two forces tends to destabilize coexistence, leading to new insights about the role of bottom-up versus top-down forces in both theory and the rocky intertidal ecosystem.

ecology↗

bioRxiv2019

Context-dependent dynamics lead to the assembly of functionally distinct pitcher-plant microbiomes

Niche construction through interspecific interactions can condition future community states on past ones. However, the extent to which such history dependency can steer communities towards functionally different states remains a subject of active debate. Using bacterial communities collected from wild pitchers of the carnivorous pitcher plant, Sarracenia purpurea, we tested the effects of history on composition and function across communities assembled in synthetic pitcher plant microcosms. We found that the diversity of assembled communities was determined by the diversity of the system at early, pre-assembly stages. Species composition was also contingent on early community states, not only because of differences in the species pool, but also because the same species had different dynamics in different community contexts. Importantly, compositional differences were proportional to differences in function, as profiles of resource use were strongly correlated with composition, despite convergence in respiration rates. Early differences in community structure can thus propagate to mature communities, conditioning their functional repertoire.

ecology↗