Biology subjects

Grady, K. L.

Publications and source records attributed to Grady, K. L..

3 recordsLinked to original sources

bioRxiv2021

Genome-centric analyses of seasonal phyllosphere microbiome activities in perennial crops

Plants and microorganisms form beneficial associations. Understanding plant-microbe interactions will inform microbiome management to enhance crop productivity and resilience to stress. Here, we apply a genome-centric approach to identify key leaf microbiome members on field-grown switchgrass and miscanthus, and quantify their activities for switchgrass over two growing seasons. We integrate metagenome and metatranscriptome sequencing from 192 leaf samples collected over key time points in crop phenology. We curated 40 focal metagenome-assembled-genomes (MAGs) and conservatively focus analysis on transcript recruitment to medium and high-quality MAGs that were <10% contaminated and >50% complete. Classes represented by these MAGs (Actinomycetia, Alpha- and Gamma-Proteobacteria, and Bacteroidota) were active and had seasonal dynamics in key functions, including enrichments in transcripts for of short chain dehydrogenase, molybdopterin oxioreductase, and polyketide cyclase in the late season. The majority of MAGs had activated stress-associated pathways, including trehalose metabolism, indole acetic acid degradation, betaine biosynthesis, and reactive oxygen species degradation, suggesting direct engagement with the host environment. We also detected seasonally activated biosynthetic pathways for terpenes (carotenoid and isoprenoids), and for various non-ribosomal peptide pathways that were poorly annotated. Overall, this study overcame laboratory and bioinformatic challenges associated with field-based leaf metatranscriptome analysis to inform potential key activities of these phyllosphere populations. These activities collectively support that leaf-associated bacterial populations are seasonally dynamic, responsive to host cues and interactively engage in feedbacks with the plant.

microbiology↗

bioRxiv2018

Assembly and seasonality of core phyllosphere microbiota on perennial biofuel crops

Perennial grasses are promising feedstocks for biofuel production. The phyllosphere (aerial surfaces) of these cellulosic crops provide a sizable surface area of microbial habitation. Leaf microbial communities may benefit the host plant, have consequence for biomass deconstruction, and interact with foliar pathogens. Here, we characterized the origins, diversity, and assembly of bacterial and archaeal communities of two perennial cellulosic feedstocks: switchgrass (Panicum virgatum L.) and miscanthus (Miscanthus x giganteus). We used 16S rRNA gene sequencing to assess microbiome structure on leaves and soils, following crop phenology every three weeks from pre-emergence through senescence for one miscanthus growing season and two consecutive switchgrass seasons. We found abundant and persistent core leaf taxa that originated in soil but were adapted for life on the leaf, rather than vagabonds that randomly disperse from air or soil. Seasonal and host-specific assembly suggested a functional relationship between the phyllosphere microbiomes and plants. This foundational knowledge advances goals to leverage native microbiomes to promote crop wellness and productivity in the field, and specifically in support of biofuels agriculture.

microbiology↗

bioRxiv2018

Hook length of the bacterial flagellum is controlled to nanometer-scale for optimal motility performance

Most bacteria swim in liquid environments by rotating one or several flagella. The long external filament of the flagellum is connected to a membrane-embedded basal-body by a flexible universal joint, the hook, which allows the transmission of motor torque to the filament. The length of the hook is controlled on a nanometer-scale by a sophisticated molecular ruler mechanism. However, why its length is stringently controlled has remained elusive. We engineered and studied a diverse set of hook-length variants of Salmonella enterica. Measurements of plate-assay motility, single-cell swimming speed and directional persistence in quasi 2D and population-averaged swimming speed and body angular velocity in 3D revealed that the motility performance is optimal around the wild type hook-length. We conclude that too short hooks may be too stiff to function as a junction and too long hooks may buckle and create instability in the flagellar bundle. Accordingly, peritrichously flagellated bacteria move most efficiently as the distance travelled per body rotation is maximal and body wobbling is minimized. Thus, our results suggest that the molecular ruler mechanism evolved to control flagellar hook growth to the optimal length consistent with efficient bundle formation. The hook-length control mechanism is therefore a prime example of how bacteria evolved elegant, but robust mechanisms to maximize their fitness under specific environmental constraints.\n\nAuthor summaryMany bacteria use flagella for directed movement in liquid environments. The flexible hook connects the membrane-embedded basal-body of the flagellum to the long, external filament. Flagellar function relies on self-assembly processes that define or self-limit the lengths of major parts. The length of the hook is precisely controlled on a nanometer-scale by a molecular ruler mechanism. However, the physiological benefit of tight hook-length control remains unclear. Here, we show that the molecular ruler mechanism evolved to control the optimal length of the flagellar hook, which is consistent with efficient motility performance. These results highlight the evolutionary forces that enable flagellated bacteria to optimize their fitness in diverse environments and might have important implications for the design of swimming micro-robots.

microbiology↗