Biology subjects

Hill, E. D.

Publications and source records attributed to Hill, E. D..

4 recordsLinked to original sources

bioRxiv2026

Distribution and dynamics of Vibrio spp. and pathogen sequences among microhabitats and monsoon seasons in Singapore's coastal waters

Marine infections are rising in temperate regions due in part to a warming climate. However, comparatively little is known about drivers of marine pathogen dynamics in the tropics where temperatures are high year-round. Vibrio bacteria are ubiquitous in both temperate and tropical marine environments, and many are important pathogens of marine organisms and humans. Here, we sampled an equatorial monsoonal site, the Singapore Strait, over 18 months and applied amplicon sequencing (16s rRNA V6-8 region) to three particle size fractions, qPCR quantitation of Vibrio spp., and generalized linear modelling with environmental variables to understand the factors that structure the Vibrio assemblage. We found that Vibrios represented the highest proportion of pathogen-related DNA sequences, with an assemblage composition influenced by microhabitats (size fractions) and monsoon seasons. Vibrio sequences were dominated by ASVs with highest identity to V. xuii, V. rotiferianus and V. caribbeanicus, and including ASVs matching agents of human disease in Singapore - V. parahaemolyticus, V. alginolyticus, and V. furnissii. Vibrio qPCR abundance was lowest in the largest size fraction (10-150 m), following planktonic DNA trends, even though pathogen-related sequences, including Vibrio, were enriched in this fraction. Temperature was a significant predictor of overall Vibrio abundance, but its effect was no longer significant after adjustment for monsoons, suggesting that the temperature association may reflect broader seasonal dynamics. Instead, effects of chlorophyll, ammonia, nitrate and suspended solids were more consistent within seasons. Furthermore, free-living and particle-associated Vibrios responded differently to environmental changes, suggesting that partitioning into microspatial habitats may lead to differences in their environmental sensitivity.

microbiology↗

bioRxiv2026

Lessons from the equator: a window on the future of vibriosis in a warming Earth

Vibrios are important aquatic human pathogens, causing gastroenteritis, wound infections, and cholera. Vibriosis (non-cholera infection) has been increasing in temperate climates due to correlation between Vibrio abundance and water temperature. However, how warming oceans differentially influence various Vibrio species, and whether incidence is higher in tropical regions, remains understudied. We assembled the first comprehensive dataset of culture-confirmed vibriosis cases outside a temperate climate from equatorial Singapore. Comparison to cases from the detailed United States (US) CDC COVIS system revealed that vibriosis incidence is over two times higher in Singapore than the United States. Causative species also differ markedly, with Vibrio fluvialis and non-toxigenic Vibrio cholerae dominating in Singapore (>40%) but are much less prominent in the United States (<15%). Singapore cases have remained stable in the last decade, while US incidence is rising rapidly, especially for V. fluvialis and V. cholerae (13% and 17% per year). Differences in causative species in Singapore and the United States suggest ecological factors may shape infection dynamics, with some species benefitting more from warming oceans, raising their equatorial prominence. Incidence is stable in Singapore, likely due to slower warming of waters near the equator. In contrast, vibriosis in the United States will likely continue to increase steadily, with changing species composition, likely becoming tropicalized.

microbiology↗

bioRxiv2023

Contrasting Effects of SARS-CoV-2 Vaccination vs. Infection on Antibody and TCR Repertoires

Antibodies and helper T cells play important roles in SARS-CoV-2 infection and vaccination. We sequenced B- and T-cell receptor repertoires (BCR/TCR) from the blood of 251 infectees, vaccinees, and controls to investigate whether features of these repertoires could predict subjects SARS-CoV-2 neutralizing antibody titer (NAbs), as measured by enzyme-linked immunosorbent assay (ELISA). We sequenced recombined immunoglobulin heavy-chain (IGH), TCR{beta} (TRB), and TCR{delta} (TRD) genes in parallel from all subjects, including select B- and T-cell subsets in most cases, with a focus on their hypervariable CDR3 regions, and correlated this AIRRseq data with demographics and clinical findings from subjects electronic health records. We found that age affected NAb levels in vaccinees but not infectees. Intriguingly, we found that vaccination and infection have an effect on non-productively recombined IGHs, suggesting an effect that precedes clonal selection. We found that repertoires binding capacity to known SARS-CoV-2-specific CD4+ TRBs performs as well as the best hand-tuned approximate or "fuzzy" matching at predicting a protective level of NAbs, while also being more robust to repertoire sample size and not requiring hand-tuning. The overall conclusion from this large, unbiased, clinically well annotated dataset is that B- and T-cell adaptive responses to SARS-CoV-2 infection and vaccination are surprising, subtle, and diffuse. We discuss methodological and statistical challenges faced in attempting to define and quantify such strong-but-diffuse repertoire signatures and present tools and strategies for addressing these challenges.

immunology↗

bioRxiv2020

Integrative systems approach reveals dynamics of microbiome-metal-ion axis in mesocosms representing tropical urban freshwater canal ecosystem

Freshwater ecosystems of tropical urban canals systems (TrUCS), are highly dynamic and experience constant pressures from interspersed effects of land-use and rain. The dynamic nature of TrUCS ecosystems presents a unique opportunity to unravel the signature interactions between the macro-organisms (top-down), sedimentary microbial communities (SedMICs), their functioning and the geochemical environment (bottom-up). A systems level understanding of the molecular and mechanistic basis of the highly dynamic behaviour that leads to specific ecosystem outcomes, is currently lacking. Therefore, a research framework to identify the direct link between top-down and bottom-up ecological effects on SedMICs in a highly dynamic urban canal sedimentary system is needed. Here, we present a framework of integrated multi-dimensional data across system-level biotic and abiotic ecological descriptors, such as environmental variables and active SedMICs. We followed the ecosystem shifts after a natural disturbance (rain) in two different anthropogenic disturbance (land-use) regimes. Shifts in profiles of metabolically active community were conserved across different land-use types, indicating resilience to perturbation is an intrinsic property of the TrUCs ecosystem. Three distinct phases, which were dominated sequentially by autotrophy, anoxic-heterotrophy and oxic-heterotrophy, were identified within these shifts. The first two phases were influenced by the bottom-up effects of specific metal-ion combinations of nitrates and sulfates with magnesium, aluminum and iron, and the third phase was triggered by top-down influences of bioturbation. This generalized systems-level approach, which provides an ecosystem-centric understanding of TrUCS and integrates them in sustainable management practices, can also be extended to other freshwater ecosystems.

ecology↗