Biology subjects

Harvey, E. L.

Publications and source records attributed to Harvey, E. L..

5 recordsLinked to original sources

bioRxiv2023

Syndiniales parasites drive species networks and are a biomarker for carbon export in the oligotrophic ocean

Microbial associations that result in phytoplankton mortality are important for carbon transport in the ocean. This includes parasitism, which in microbial food webs, is dominated by the marine alveolate group, Syndiniales. Parasites are expected to contribute to carbon recycling via host lysis; however, knowledge on host dynamics and correlation to carbon export remain unclear and limit the inclusion of parasitism in biogeochemical models. We analyzed a 4-year 18S rRNA metabarcoding dataset (2016-2019), performing network analysis for twelve discrete depths (1- 1000 m) to determine Syndiniales-host associations in the seasonally oligotrophic Sargasso Sea. Analogous water column and sediment trap data were included to define environmental drivers of Syndiniales and their correlation with particulate carbon flux (150 m). Syndiniales accounted for 48-74% of network edges, most often associated with Dinophyceae and Arthropoda (mainly copepods) at the surface and Rhizaria (Polycystinea, Acantharea, and RAD-B) in the aphotic zone. Unlike other major groups, Syndiniales were significantly (and negatively) correlated with particulate carbon flux, suggesting parasites may drive flux attenuation through remineralization. Examination of Syndiniales amplicons revealed a range of depth patterns, including specific ecological niches and vertical connection among a subset (19%) of the community, the latter implying sinking of parasites (infected hosts or spores) on particles. Our findings point to the use of Syndiniales as biomarkers of carbon export, highlighting their importance for marine food webs and biogeochemistry. Significance StatementSyndiniales parasites are widespread in the ocean and represent a potentially important, albeit poorly resolved, source of carbon recycling. Here, we assess Syndiniales population dynamics, trophic relationships, and links to carbon export in the Sargasso Sea. Species networks at all depths were driven by Syndiniales, with parasite-host relationships varying with depth based on shifts in host composition. Syndiniales were the only eukaryote group to be significantly (and negatively) correlated with particulate carbon flux, indicating their contribution to flux attenuation via remineralization. Yet, a subset of parasites was vertically connected between photic and aphotic zones, suggesting continued export. Our findings elevate the critical role of Syndiniales in marine microbial systems and reveal their potential use as biomarkers for carbon export.

microbiology↗

bioRxiv2021

The long-term effects of repeated heroin vapor inhalation during adolescence on measures of nociception and anxiety-like behavior in adult Wistar rats

RationaleAdolescents represent a vulnerable group due to increased experimentation with illicit substances that is often associated with the adolescent period, and because adolescent drug use can result in long-term effects that differ from those caused by drug use initiated during adulthood. ObjectivesThe purpose of the present study was to determine the effects of repeated heroin vapor inhalation during adolescence on measures of nociception, and anxiety-like behavior during adulthood in female and male Wistar rats. MethodsRats were exposed twice daily to 30-minutes of heroin vapor from post-natal day (PND) 36 to PND 45. At 12 weeks of age, baseline thermal nociception was assessed across a range of temperatures with a warm-water tail-withdrawal assay. Anxiety-like behavior was assessed in an elevated plus-maze (EPM) and activity was measured in an open field arena. Starting at 23 weeks of age, baseline thermal nociception was re-assessed, nociception was determined after acute heroin or naloxone injection, and anxiety-like behavior was redetermined in the EPM. ResultsAdolescent heroin inhalation altered baseline thermal nociception in female rats at 12 weeks of age and in both female and male rats at [~]23 weeks. Heroin-treated animals exhibited anxiety-like behavior when tested in the elevated plus-maze, showed blunted heroin-induced analgesia, but exhibited no effect on naloxone-induced hyperalgesia. ConclusionsThe present study demonstrates that heroin vapor inhalation during adolescence produces behavioral and physiological consequences in rats that persist well into adulthood.

pharmacology and toxicology↗

bioRxiv2021

Investigating temperature effects on coastal microbial populations and trophic interactions with 16S and 18S rRNA metabarcoding

Temperature is a universal driver of microbial life, with rising sea surface temperatures expected to differentially influence the physiology, biodiversity, and distribution of bacteria and plankton. The impact of ocean warming on microbial interactions remains unclear, despite the importance of these relationships for ecosystem functioning. We employed weekly to monthly 18S and 16S rRNA gene amplicon metabarcoding over a full year (33 d) in a subtropical estuary, investigating microbial population dynamics and network interactions with respect to a temperature gradient (9-31{degrees}C). Certain microbes (e.g., Acidimicrobiia, Nitrososphaeria, and Syndiniales) increased in relative abundance with rising temperatures (Spearman {rho} > 0.69), whereas other groups (e.g., Alpha- and Gammaproteobacteria, Bacillariophyta, and Dinophyceae) slightly decreased, became saturated, or remained stable. With network analysis, we observed an increase in 18S- 18S interactions in warm (23-31{degrees}C) vs. cold (<23{degrees}C) temperatures, largely involving Syndiniales, Bacillariophyta, and Dinophyceae ASVs. Bacteria ASVs were more connected to other microbes (higher degree and centrality) and became more prominent in the cold network, highlighted by well-established cross-domain relationships (e.g., diatom-bacteria) and positive interactions among bacteria (e.g., SAR11 and Rhodobacterales). These efforts highlight the types of interactions that may be more common under changing temperatures, with implications for modeling biogeochemistry and assessing ecosystem health.

ecology↗

bioRxiv2020

Antinociceptive, hypothermic, and appetitive effects of vaped and injected Δ9-tetrahydrocannabinol (THC) in rats: exposure and dose-effect comparisons by strain and sex

Advances in drug vapor exposure systems utilizing e-cigarette technology have enabled evaluation of {Delta}-9-tetrahydrocannabinol (THC) vapor effects in laboratory animals. The purpose of this study was to 1) establish a range of parameters of THC vapor exposure in rats sufficient to produce a behavioral dose-effect curve in a battery of tasks sensitive to THC; 2) to investigate sex differences in the effects of THC vapor exposure and THC injection (intraperitoneal, IP) on these behaviors in two strains of outbred rats. Male and female Wistar and Sprague Dawley rats (N=22, 5-6/group) received THC via IP injection (1-20 mg/kg) and passive exposure to THC vapor (200 mg/ml; 5 conditions) in a within subject design. The effects of vaped and injected THC were determined using the tail-withdrawal assay for nociception, rectal measurements of body temperature, and progressive-ratio responding for food pellets. Plasma THC concentrations were assessed after 10 mg/kg IP THC or THC vapor. THC produced dose and exposure-dependent antinociception and hypothermia. THC vapor produced inverted U-shaped effects in motivation to obtain food, while IP THC reduced PR breakpoints. Plasma THC concentrations were higher after 10 mg/kg IP THC (152 ng/mL) compared to the highest vapor exposure condition tested (38 ng/mL). THC vapor exposure produces reliable, dose-orderly effects on nociception, body temperature, and food-maintained behavior that is comparable to effects observed after IP THC. There are considerable differences between the time course of behavioral outcomes produced by these two different routes of administration.

animal behavior and cognition↗

bioRxiv2020

Bacterial quorum sensing signal arrests phytoplankton cell division and protects against virus-induced mortality

Interactions between phytoplankton and heterotrophic bacteria fundamentally shape marine ecosystems. These interactions are driven by the exchange of compounds, however, linking these chemical signals, their mechanisms of action, and resultant ecological consequences remains a fundamental challenge. The bacterial signal 2-heptyl-4-quinolone (HHQ), induces immediate cellular stasis in the coccolithophore, Emiliania huxleyi, however, the mechanism responsible remains unknown. Here, we show that HHQ exposure leads to the accumulation of DNA damage in phytoplankton and prevents its repair. While this effect is reversible, HHQ-exposed phytoplankton are also protected from viral mortality, ascribing a new role of quorum sensing signals in regulating multi-trophic interactions. Further results demonstrate global HHQ production potential and the first in situ measurements of HHQ which coincide with areas of enhanced micro- and nanoplankton biomass. Our results support bacterial communication signals as emerging players, providing a new mechanistic framework for how compounds may contribute to structure complex marine microbial communities.

microbiology↗