Biology subjects

Hedlund, B. P.

Publications and source records attributed to Hedlund, B. P..

3 recordsLinked to original sources

bioRxiv2020

Diversity and Distribution of a Novel Genus of Hyperthermophilic Aquificae Viruses Encoding a Proof-reading Family-A DNA Polymerase

Despite the high abundance of Aquificae in many geothermal systems, these bacteria are difficult to culture and no viruses infecting members of this phylum have been isolated. Here, we describe the complete, circular dsDNA Uncultivated Virus Genome (UViG) of Thermocrinis Octopus Spring virus (TOSV), derived from metagenomic data, along with eight related UViGs representing three additional species, Thermocrinis Great Boiling Spring virus (TGBSV), Aquificae Josephs Coat Spring Virus (AJCSV), and Aquificae Conch Spring Virus (ACSV). Four near-complete UViGs, ranged from 37,256 bp to 41,208 bp and encoded 48 to 53 open reading frames. Despite low overall similarity between viruses from different hot springs, the genomes shared a high degree of synteny, and encoded numerous genes for nucleotide metabolism, including a polyprotein PolA-type polymerase with likely accessory functions, a DNA Pol III beta subunit (sliding clamp), a thymidylate kinase, a DNA gyrase, a helicase, and a DNA methylase. Also present were conserved genes predicted to code for phage capsids, large and small terminases, portal protein, holin, and lytic transglycosylase, all consistent with a distant relatedness to cultivated Caudovirales. TOSV and TGBSV had the highest coverage in their respective metagenomes and are predicted to infect Thermocrinis ruber and Thermocrinis jamiesonii, respectively, as multiple CRISPR spacers matching the viral genomes were identified within Thermocrinis ruber OC1/4T and Thermocrinis jamiesonii GBS1T. Based on the predicted, unusual bi-directional replication strategy, low sequence similarity to known viral genomes, and a unique position in gene-sharing networks, we propose a new putative genus, Pyrovirus, in the order Caudovirales.

microbiology↗

bioRxiv2020

Microbiome shifts associated with the introduction of wild Atlantic horseshoe crabs (Limulus polyphemus) into a touch-tank exhibit

The Atlantic horseshoe crab (Limulus polyphemus) is a common marine aquarium species and model organism for research. There is potential monetary and conservation value in developing a stable captive population of horseshoe crabs, however, one major impediment to achieving captivity is a lack of knowledge regarding captive diseases. We utilized 16S rRNA gene amplicon sequencing to track changes in the microbiomes of four body locations in three wild-caught (tracked over 14 months in captivity) and three tank-acclimated (>2 years in captivity) adult L. polyphemus in a touch tank at Shark Reef Aquarium at Mandalay Bay in Las Vegas, NV. The wild population hosted diverse and distinct microbiomes on the carapace (737 amplicon sequence variants or ASVs), cloaca (1078 ASVs), gills (941 ASVs), and oral cavity (1193 ASVs), which were dominated by classes Gammaproteobacteria, Bacteroidia, and Alphaproteobacteria. A rapid decline in richness across all body locations was observed within 1 month of captivity, with tank-acclimated (>2 years) animals having <5% of the initial microbiome richness and a nearly completely restructured microbial community. The carapace, oral cavity, and gills of the tank-acclimated animals hosted abundant populations of Aeromonas (>60%) and Pseudomonas (>20%), both of which are known opportunistic pathogens of aquatic animals and can express chitinases, providing a plausible mechanism for the development of the carapace lesion pathology observed in this and other studies. These results provide an important baseline on the microbiomes of both wild and tank-acclimated horseshoe crabs and underscore the need to continue to investigate how native microbial populations may protect animals from pathogens.

microbiology↗

bioRxiv2019

A high-fat/high-protein, Atkins-type diet exacerbates Clostridioides (Clostridium) difficile infection in mice, whereas a high-carbohydrate diet protects

Clostridioides difficile (formerly Clostridium difficile) infection (CDI) can result from the disruption of the resident gut microbiota. Western diets and popular weight-loss diets drive large changes in the gut microbiome; however, the literature is conflicted with regard to the effect of diet on CDI. Using the hypervirulent strain C. difficile R20291 (RT027) in a mouse model of antibiotic-induced CDI, we assessed disease outcome and microbial community dynamics in mice fed two high-fat diets in comparison with a high-carbohydrate diet and a standard rodent diet. The two high-fat diets exacerbated CDI, with a high-fat/high-protein, Atkins-like diet leading to severe CDI and 100% mortality, and a high-fat/low-protein, medium-chain triglyceride (MCT)-like diet inducing highly variable CDI outcomes. In contrast, mice fed a high-carbohydrate diet were protected from CDI, despite high refined carbohydrate and low fiber content. 28 members of the Lachnospiraceae and Ruminococcaceae decreased in abundance due to diet and/or antibiotic treatment; these organisms may compete with C. difficile for amino acids and protect healthy animals from CDI in the absence of antibiotics. Together, these data suggest that antibiotic treatment might lead to loss of C. difficile competitors and create a favorable environment for C. difficile proliferation and virulence that is intensified by high-fat/high-protein diets; in contrast, high-carbohydrate diets might be protective regardless of the source of carbohydrate.

microbiology↗