Biology subjects

Murrell, C.

Publications and source records attributed to Murrell, C..

4 recordsLinked to original sources

bioRxiv2026

Genomes of Betacoronavirus gravedinis from white-footed mice in New York City and a phylogenetically weighted model of its probable distribution in North America

Rodents are an important reservoir of zoonotic viruses and are ubiquitously present in densely populated urban areas. Betacoronaviruses in the Embecovirus lineage are well known to infect both humans and animals and have established rodent reservoirs. Here three Betacoronavirus gravedinis genomes were sequenced and characterized in white footed mice (Peromyscus leucopus, commonly white footed mice) collected in New York City, the second most populous city in North America. The genomes were distinct from mouse hepatitis virus (MHV), the prototype mouse betacoronavirus, and highly similar and identical in one case to previously characterized B. gravedinis sequences from white footed mice in Connecticut. Codon aware evolutionary models were used to identify specific sites under positive selection within the spike protein of B. gravedinis. A novel method was developed to predict the probable geographic distribution of the virus using publicly available data from the Global Biodiversity Information Facility to generate a weighted distribution map highlighting overlapping potential host ranges based on the evolutionary distance using a high resolution cytocrome B (CYTB) phylogeny of rodent species with potentially overlapping ranges. Our models predict three current hotspots of circulation in North America under different possible transmission regimes, and an additional fourth hotspot was predicted to arise in a warming future. This study highlights the continued need for biodiversity-informed surveillance of potential zoonotic pathogens in rodents.

microbiology↗

bioRxiv2024

A simple action reduces food intake and obesity in mice

Diets that are high in fat cause over-eating and weight gain in multiple species of animals, suggesting that high dietary fat is sufficient to cause obesity. However, high-fat diets are typically provided freely to animals in obesity experiments, so it remains unclear if high-fat diets would still cause obesity if they required more effort to obtain. We hypothesized that unrestricted and easy access is necessary for high-fat diet induced over-eating, and the corollary that requiring mice to perform small amounts of work to obtain high-fat diet would reduce high-fat diet intake and associated weight gain. To test this hypothesis, we developed a novel home-cage based feeding device that either provided high-fat diet freely, or after mice poked their noses into a port one time - a simple action that is easy for them to do. We tested the effect of this intervention for six weeks, with mice receiving all daily calories from high-fat diet, modifying only how they accessed it. Requiring mice to nose-poke to access high-fat diet reduced intake and nearly completely prevented the development of obesity. In follow up experiments, we observed a similar phenomenon in mice responding for low-fat grain-based pellets that do not induce obesity, suggesting a general mechanism whereby animals engage with and consume more food when it is freely available vs. when it requires a simple action to obtain. We conclude that unrestricted access to food promotes overeating, and that a simple action such as a nose-poke can reduce over-eating and weight gain in mice. This may have implications for why over-eating and obesity are common in modern food environments, which are often characterized by easy access to low-cost unhealthy foods.

animal behavior and cognition↗

bioRxiv2020

Investigating the role of root exudates in recruiting Streptomyces bacteria to the Arabidopsis thaliana root microbiome

Streptomyces species are saprophytic soil bacteria that produce a diverse array of specialised metabolites, including half of all known antibiotics. They are also rhizobacteria and plant endophytes that can promote plant growth and protect against disease. Several studies have shown that streptomycetes are enriched in the rhizosphere and endosphere of the model plant Arabidopsis thaliana. Here, we set out to test the hypothesis that they are attracted to plant roots by root exudates, and specifically by the plant phytohormone salicylate, which they might use as a nutrient source. We confirmed a previously published report that salicylate over-producing cpr5 plants are colonised more readily by streptomycetes but found that salicylate-deficient sid2-2 and pad4 plants had the same levels of root colonisation by Streptomyces bacteria as the wild-type plants. We then tested eight genome sequenced Streptomyces endophyte strains in vitro and found that none were attracted to or could grow on salicylate as a sole carbon source. We next used 13CO2 DNA stable isotope probing to test whether Streptomyces species can feed off a wider range of plant metabolites but found that Streptomyces bacteria were outcompeted by faster growing proteobacteria and did not incorporate photosynthetically fixed carbon into their DNA. We conclude that, given their saprotrophic nature and under conditions of high competition, streptomycetes most likely feed on more complex organic material shed by growing plant roots. Understanding the factors that impact the competitiveness of strains in the plant root microbiome could have consequences for the effective application of biocontrol strains. ImportanceStreptomyces bacteria are ubiquitous in soil but their role as rhizobacteria is less well studied. Our recent work demonstrated that streptomycetes isolated from A. thaliana roots can promote growth and protect against disease across plant species and that plant growth hormones can modulate the production of bioactive specialised metabolites by these strains. Here we used 13CO2 DNA stable isotope probing to identify which bacteria feed on plant metabolites in the A. thaliana rhizosphere and, for the first time, in the endosphere. We found that Streptomyces species are outcompeted for these metabolites by faster growing proteobacteria and instead likely subsist on more complex organic material such as cellulose derived from plant cell material that is shed from the roots. This work thus reveals the "winners and losers" in the battle between soil bacteria for plant metabolites and could inform the development of methods to apply streptomycetes as plant growth-promoting agents.

microbiology↗

bioRxiv2019

Investigating the role of exudates in recruiting Streptomyces bacteria to the Arabidopsis thaliana root microbiome

Streptomyces bacteria are ubiquitous in soils and are well-known for producing secondary metabolites, including antimicrobials. Increasingly, they are being isolated from plant roots and several studies have shown they are specifically recruited to the rhizosphere and the endosphere of the model plant Arabidopsis thaliana. Here we test the hypothesis that Streptomyces bacteria have a beneficial effect on A. thaliana growth and could potentially be used as plant probiotics. To do this, we selectively isolated streptomycetes from surface washed A. thaliana roots and generated high quality genome sequences for five strains which we named L2, M2, M3, N1 and N2. Re-infection of A. thaliana plants with L2, M2 and M3 significantly increased plant biomass individually and in combination whereas N1 and N2 had a negative effect on plant growth, likely due to their production of polyene natural products which can bind to phytosterols and reduce plant growth. N2 exhibits broad spectrum antimicrobial activity and makes filipin-like polyenes, including 14-hydroxyisochainin which inhibits the Take-all fungus, Gaeumannomyces graminis var. tritici. N2 antifungal activity as a whole was upregulated ~2-fold in response to indole-3-acetic acid (IAA) suggesting a possible role during competition in the rhizosphere. Furthermore, coating wheat seeds with N2 spores protected wheat seedlings against Take-all disease. We conclude that at least some soil dwelling streptomycetes confer growth promoting benefits on A. thaliana while others might be exploited to protect crops against disease. ImportanceIt is vital that we reduce our reliance on agrochemicals and there is increasing interest in using bacterial strains to promote plant growth and protect against disease. Our study follows up reports that Arabidopsis thaliana specifically recruits Streptomyces bacteria to its roots. In particular, we test the hypothesis that these bacteria can offer benefits to their A. thaliana hosts and that strains isolated from these plants might be used as probiotics. We isolated Streptomyces strains from surface washed A. thaliana roots and genome sequenced five phylogenetically distinct strains. Genome mining and bioassays indicated that all five strains have plant growth promoting properties, including production of IAA, siderophores and ACC deaminase activity. Three strains significantly increased A. thaliana growth in vitro and when applied in combination in soil. Another produces potent filipin-like antifungal metabolites and we used it as a seed coating to protect germinating wheat seeds against the fungal pathogen Gaeumannomyces graminis var. tritici (wheat Take-all fungus). We conclude that introducing an optimal combination of Streptomyces strains into the root microbiome can provide significant benefits to plants.

microbiology↗