Biology subjects

Bandopadhyay, S.

Publications and source records attributed to Bandopadhyay, S..

4 recordsLinked to original sources

bioRxiv2026

Drought duration does not impact soil microbiome resilience

Increasing global droughts exert large but poorly understood effects on the microbial communities and ecology of soil. Microbial communities generally show resilience and return to pre-drought conditions when short-term droughted soils are rewet; soils exposed to long-term drought, however, often show a lag upon rewetting, after which microbial communities may or may not return to their pre-stressed conditions. Though short-term droughts have been widely studied, long-term drought manipulation experiments remain rare, especially those that compare microbial response to short-term and long-term drought in tandem. We conducted a 1000-day drought simulation in controlled laboratory conditions with soil cores collected from a tidal freshwater ecosystem in Washington state, USA, and subsequently exposed them to rewetting for two weeks. We also included short-term (30-day and 90-day) drought and rewet treatments to directly compare microbial community and organic matter responses across drought durations. We found distinct microbial taxa belonging to Firmicutes and Actinobacteria enriched after the 1000-day drought, but not after the short-term droughts. While we hypothesized that the microbial community would recover from a short-term drought after rewetting to resemble pre-drought conditions, our results revealed community dissimilarities between rewet and pre-drought conditions across all drought durations. These findings suggest unique microbial life history strategies within certain microbial phyla that make them successful colonizers during an extended drought period, and the influence of environmental and physiological context on microbial responses to rewetting. ImportanceDroughts are increasing in frequency and intensity globally with severe implications for ecosystem services and soil functions. It is important to understand how long-term drought impacts soil microbial communities and organic matter chemistry to better predict future ecosystem responses to sustained moisture deficit conditions. We subjected soils to short-term (30 and 90 days) and long-term (1000 days) drought treatments and subsequently rewetted them to understand microbiome recovery to pre-drought conditions. Our results showed that prolonged drought drastically changes the microbial community and soil organic matter profile compared to short-term drought. While we expected the soil microbiome to recover upon rewetting after short-term drought, our results showed an altered microbiome composition, compared to pre-drought conditions, for both short-and long-term drought, suggesting microbial responses to soil rewetting was independent of drought duration imposed. These results provide important insights into soil biological and chemical functions that remain sensitive to change under fluctuating soil moisture conditions and future drought scenarios.

ecology↗

bioRxiv2025

Activation dynamics and assembly of root zone soil bacterial communities in response to stress-associated phytohormones

Plants can "cry for help" to recruit supportive microbiome members during stressful conditions. We evaluated the activation dynamics of root zone soil bacteria in response to phytohormones produced when plants are stressed, hypothesizing that the activated taxa support plant resilience. We conducted a 2-week laboratory experiment using mesocosms of root zone soil collected from two different crops: the annual legume common bean (Phaseolus vulgaris L.) and the perennial grass switchgrass (Panicum virgatum). We inactivated the microbiome by drying and then treated the soils with either abscisic acid, salicylic acid, a carrier control (methanol), or water, and then quantified the reactivation dynamics of bacterial populations over time, at one, 7, and 14 days after phytohormone addition, using amplicon sequencing of 16S rRNA and rDNA. There were several Actinobacterial taxa that switched from an average population-inactive to a population-active state after exposure to abscisic acid and salicylic acid, with Microbispora lineages switching especially noted. Some taxa were activated only in one crops soil, and some were activated in both crops soils in response to the same phytohormone. This work suggests that different bacteria have different specificities to phytohormones as plant stress signals and provides insights into understanding the mechanisms by which stressed plants may "cry for help" to recruit bacteria from the root zone to the rhizosphere. ImportanceGlobal food security is an urgent societal challenge that has been intensified by climate change and other anthropogenic stressors placed on the environment. Microbial bioinoculants are a promising solution to improve crop health and resilience, but ensuring their persistence and activation in the field remains a challenge. This study examined how dormant root-zone associated bacteria reactivate after exposure to the plant stress hormones abscisic acid and salicylic acid. The experiment revealed that certain bacteria taxa could reactivate in response to these plant stress signals and persist for at least two weeks. This work advances understanding of the potential cues for reactivation of beneficial plant-associated microbes and supports goals toward developing microbial solutions for sustainable agriculture.

microbiology↗

bioRxiv2023

Disentangling plant- and environment-mediated drivers of active rhizosphere bacterial community dynamics during short-term drought

BackgroundMitigating the effects of climate stress on crops is important for global food security. The microbiome associated with plant roots, henceforth, the rhizobiome, can harbor beneficial microbes that alleviate stress impacts. However, the factors influencing the recruitment of the rhizobiome during stress are unclear. We conducted an experiment to understand bacterial rhizobiome responses to short-term drought for two crop species: switchgrass and common bean. We used 16S rRNA and 16S rRNA gene sequencing to investigate the impact of drought severity on the recruitment of active bacterial rhizobiome members. We included planted and unplanted conditions to distinguish the environment-versus plant-mediated drivers of the active rhizobiome. ResultsThough each crop had a distinct rhizobiome, there were differences in the active microbiome structure between drought and watered and between planted and unplanted treatments. Despite their different community structures, the drought rhizobiome dynamics were similar across the two crops. However, the presence of a plant more strongly explained the rhizobiome variation in bean (17%) than in switchgrass (3%), with a small effect of plant mediation during drought only observed for the bean rhizobiome. The switchgrass rhizobiome was stable despite differences in the rhizosphere metabolite profiles between planted and unplanted treatments. Specifically, steroidal saponins and diterpennoids were enriched in drought, planted switchgrass soils. ConclusionsWe conclude that rhizobiome benefits to resist short-term drought are crop-specific, with the possibility of decoupling of plant exudation and rhizobiome responses, as we observed in switchgrass. We propose bacterial taxa uniquely associated with common bean plants during the short-term drought, which could be further evaluated to determine any plant benefit during drought.

microbiology↗

bioRxiv2019

Structural and Functional Responses of Soil Microbial Communities to Biodegradable Plastic Film Mulching in Two Agroecosystems

Polyethylene (PE) plastic mulch films are used globally in crop production but incur considerable disposal and environmental pollution issues. Biodegradable plastic mulch films (BDMs), an alternative to PE-based films, are designed to be tilled into the soil where they are expected to be mineralized to carbon dioxide, water and microbial biomass. However inadequate research regarding the impacts of repeated incorporation of BDMs on soil microbial communities has partly contributed to limited adoption of BDMs. In this study, we evaluated the effects of BDM incorporation on soil microbial community structure and function over two years in two geographical locations: Knoxville, TN, and in Mount Vernon, WA. Treatments included four plastic BDMs, a completely biodegradable cellulose mulch, a non-biodegradable PE mulch and a no mulch plot. Bacterial community structure determined using 16S rRNA amplicon sequencing revealed significant differences by location and season. Differences in bacterial communities by mulch treatment were not significant for any season in either location, except for Fall 2015 in WA where differences were observed between BDMs and no-mulch plots. Extracellular enzyme rate assays were used to characterize communities functionally, revealing significant differences by location and sampling season in both TN and WA but minimal differences between BDMs and PE treatments. Limited effects of BDM incorporation on soil bacterial community structure and soil enzyme activities when compared to PE suggest that BDMs have comparable influences on soil microbial communities, and therefore could be considered an alternative to PE.\n\nImportancePlastic film mulches increase crop yields and improve fruit quality. Most plastic mulches are made of polyethylene (PE), which is poorly degradable, resulting in undesirable end-of-life outcomes. Biodegradable mulches (BDMs) may be a sustainable alternative to PE. BDMs are made of polymers which can be degraded by soil microbial enzymes, and are meant to be tilled into soil after use. However, uncertainty about impacts of tilled-in BDMs on soil health has restricted adoption of BDMs. Our previous research showed BDMs did not have a major effect on a wide range of soil quality indicators (Sintim et al. 2019); here we focus on soil microbial communities, showing that BDMs do not have detectable effects on soil microbial communities and their functions, at least over the short term. This informs growers and regulators about use of BDMs in crop production, paving a way for an agricultural practice that reduces environmental plastic pollution.

microbiology↗