Biology subjects

White, P. L.

Publications and source records attributed to White, P. L..

4 recordsLinked to original sources

bioRxiv2026

Glacier-induced upwelling shapes microbial communities in Arctic marine systems

The Canadian Arctic Archipelago (CAA) is warming at an unprecedented rate, leading to sea ice loss and glacial retreat. Marine-terminating (tidewater) glaciers can fuel summertime marine productivity by delivering nutrient-rich deep waters via upwelling to the surface ocean. While the impact of glacier-induced upwelling has been well-studied in the context of phytoplankton and primary productivity, its effects on broader marine microbial communities remain poorly understood. We investigated how glacier-driven upwelling shapes marine microbial (bacterial and archaeal) communities across a series of sites in the CAA. At upwelling sites, the upper 50 m of the water column exhibited elevated nutrient concentrations and physical characteristics that resembled deeper waters, which were associated with differences in microbial community composition relative to non-upwelling sites. Our results indicate that upwelling influences microbial communities in surface waters in two ways. It directly introduces typically deeper-water-associated taxa into surface waters and reshapes ecological niches by enhancing nutrient supply and stimulating primary production, indirectly driving changes in microbial communities. The enrichment of Candidatus Nitrosopumilus, a deep water nitrifier, likely affects nitrogen cycling and raises the possibility of active nitrification in surface waters. Likewise, the increased abundance of taxa known to be associated with phytoplankton-derived organic matter in upwelling regions suggests an enhanced capacity to process organic matter generated from elevated primary productivity. Ultimately, as tidewater glaciers continue to retreat, the resulting changes in the glacially-driven upwelling regime will likely shift marine microbial communities towards assemblages adapted to less productive ecosystems, with implications for nutrient cycling in these systems. ImportanceClimate change has a disproportionate impact on the Arctic, with rising temperatures causing increased marine-terminating glacier retreat and changes in the marine water column structure. The consequent loss of the ability of these glaciers to upwell deep water to the surface ocean results in a reduction of nutrient delivery and mixing in these ecosystems. Previous work has highlighted the importance of marine-terminating glaciers in sustaining phytoplankton productivity during the summer season through this delivery of deep-water nutrients to the surface ocean. The impact of glacially-induced upwelling on marine bacterial and archaeal communities, however, remains underexplored. We found that in regions with glacially-driven upwelling, the surface ocean showed enrichment of phytoplankton-associated taxa and nitrifiers commonly associated with deep waters. This work underscores the role of glacially-driven upwelling in structuring both microbial communities and nutrient cycling, suggesting that glacier loss could reshape community composition and biogeochemical processes in a rapidly changing Arctic.

microbiology↗

bioRxiv2024

Seasonal patterns in b-vitamins and cobalamin co-limitation in the Northwest Atlantic

B-vitamins are important co-enzymes that have long been hypothesized to play key roles in marine ecosystems. However, environmental measurements remain scarce, which limits our understanding of their potential impact. Here, we present mass spectrometry-based measurements of b-vitamins (B1, B2, B3, B5, B6, B12) and related vitamers along a transect in the Northwest Atlantic Ocean, in both particulate phase and dissolved in seawater, seasonally over 5 years, and couple this with targeted investigations of the impact of B12 (cobalamin) on phytoplankton growth. We show that these metabolites are present at femto to pico-molar concentrations and demonstrate that season explains most variance in particulate phase b-vitamins but not dissolved, offering further evidence that metabolite inventories in these two phases are often decoupled. We find correlations between particulate organic carbon with particulate B1 and B3, and between chlorophyll a and particulate B2 and DMB in fall but not spring, indicating unique seasonal drivers of vitamin inventories. Of all measured vitamins, only cobalamin was enriched in the particulate over dissolved phase, predominantly in spring. We documented nitrogen and cobalamin co-limitation of phytoplankton growth during spring bloom decline, when dissolved cobalamin is seemingly drawn down, but not during fall, when dissolved cobalamin concentrations remain elevated. These seasonal differences may be underpinned by the increased importance of cobalamin remodeling and recycling during the fall. This study provides insights into the absolute concentrations, stoichiometry, and variability of b-vitamins in the ocean and offers evidence that cobalamin exerts seasonally-varying controls on Northwest Atlantic marine ecosystems.

microbiology↗

bioRxiv2023

Universal Digital High Resolution Melt for the detection of pulmonary mold infections

BackgroundInvasive mold infections (IMIs) such as aspergillosis, mucormycosis, fusariosis, and lomentosporiosis are associated with high morbidity and mortality, particularly in immunocompromised patients, with mortality rates as high as 40% to 80%. Outcomes could be substantially improved with early initiation of appropriate antifungal therapy, yet early diagnosis remains difficult to establish and often requires multidisciplinary teams evaluating clinical and radiological findings plus supportive mycological findings. Universal digital high resolution melting analysis (U-dHRM) may enable rapid and robust diagnosis of IMI. This technology aims to accomplish timely pathogen detection at the single genome level by conducting broad-based amplification of microbial barcoding genes in a digital polymerase chain reaction (dPCR) format, followed by high-resolution melting of the DNA amplicons in each digital reaction to generate organism-specific melt curve signatures that are identified by machine learning. MethodsA universal fungal assay was developed for U-dHRM and used to generate a database of melt curve signatures for 19 clinically relevant fungal pathogens. A machine learning algorithm (ML) was trained to automatically classify these 19 fungal melt curves and detect novel melt curves. Performance was assessed on 73 clinical bronchoalveolar lavage (BAL) samples from patients suspected of IMI. Novel curves were identified by micropipetting U-dHRM reactions and Sanger sequencing amplicons. ResultsU-dHRM achieved an average of 97% fungal organism identification accuracy and a turn-around-time of 4hrs. Pathogenic molds (Aspergillus, Mucorales, Lomentospora and Fusarium) were detected by U-dHRM in 73% of BALF samples suspected of IMI. Mixtures of pathogenic molds were detected in 19%. U-dHRM demonstrated good sensitivity for IMI, as defined by current diagnostic criteria, when clinical findings were also considered. ConclusionsU-dHRM showed promising performance as a separate or combination diagnostic approach to standard mycological tests. The speed of U-dHRM and its ability to simultaneously identify and quantify clinically relevant mold pathogens in polymicrobial samples as well as detect emerging opportunistic pathogens may provide information that could aid in treatment decisions and improve patient outcomes.

microbiology↗

bioRxiv2021

Tracing patterns of evolution and acquisition of drug resistant Aspergillus fumigatus infection from the environment using population genomics

Infections caused by opportunistic fungal pathogens are increasingly resistant to first-line azole antifungal drugs. However, despite its clinical importance, little is known about the extent to which susceptible patients acquire infection from drug resistant genotypes in the environment. Here, we present a population genomic analysis of the mould Aspergillus fumigatus from across the United Kingdom and Republic of Ireland. First, we show occurrences where azole resistant isolates of near identical genotypes were obtained from both environmental and clinical sources, indicating with high confidence the infection of patients with resistant isolates transmitted from the environment. Second, we find that the fungus is structured into two clades ( A and B) with little interclade recombination and the majority of environmental azole resistance genetically clustered inside Clade A. Genome-scans show the impact of selective sweeps across multiple regions of the genome. These signatures of positive selection are seen in regions containing canonical genes encoding fungicide resistance in the ergosterol biosynthetic pathway, whilst other regions under selection have no defined function. Phenotyping identified genes in these regions that could act as modifiers of resistance showing the utility of reverse genetic approaches to dissect the complex genomic architecture of fungal drug resistance. Understanding the environmental drivers and genetic basis of evolving fungal drug resistance needs urgent attention, especially in light of increasing numbers of patients with severe viral respiratory tract infections who are susceptible to opportunistic fungal superinfections.

genomics↗