Overview

Project Highlights:

  • Reconstruct hundreds of novel microbial genomes from the Thames watershed
  • Track transmission of AMR genes between organisms
  • Resolve environmental origin of AMR genes in pathogens

The development of resistance to antibiotics by human pathogens is one of the greatest threats currently faced by mankind. It has been estimated that if antibiotics become ineffective then routine operations such as hip-replacements could lead to death for 1 in 6 patients. Until recently this was studied purely as a medical problem but it is now realised that the environment has a key role to play as a reservoir of antimicrobial resistance (AMR) genes because AMR genes can be transferred from environmental organisms to pathogens by horizontal gene transfer. The challenge is how to study AMR in environmental organisms that consist of a complex community of possibly unculturable organisms. Metagenomics the sequencing of DNA from the entire community in situ provides a solution to this problem.

The objective of this principally computational project will be to exploit a combination of newly available metagenome sequence data and novel bioinformatics techniques to better understand the role played by the environment in AMR. Central to the project will be the Thames Metagenome Database (TMD), which is being generated by a NERC funded consortium that includes the project partners (NE/M011259/1). It will consist of over a terabase of microbial DNA metagenome sequence sampled from 30 locations in the Thames catchment at two separate time points together with antibiotic concentrations. These locations have been chosen to span a range of anthropogenic impacts such as intensive agriculture and wastewater treatment plants (WTPs).

The TMD will provide an invaluable resource on the prevalence of AMR genes in the environment but in its raw form it will consist of billions of short reads. To unlock its full potential we will assemble these reads together and then use algorithms developed by Dr Quince (e.g. CONCOCT) to link the assemblies into genomes. This will enable us to determine which environmental organisms possess which AMR genes. We will then search for these same genes in pathogen genome databases and additional publicly available metagenomes from environments such as the human gut (HMP) and the sea (Tara Oceans). This will provide a global picture of the role of the environment as a reservoir for pathogen AMR.

69 samplings sites (red pins) selected for proximity to WWTPs (green houses), and fish farms (blue fish). 30 of these sites have been selected for the TMD.

Methodology

The TMD will provide us with metagenome sequences from microbial communities at multiple times from the Thames catchment (TMD – NE/M011259/1). We will pool these samples together and co-assemble the short reads into longer fragments or contigs. This will generate many hundreds of thousands of contigs deriving from thousands of microbial genomes. We will use statistical techniques that exploit the fact that contigs from the same genome will co-occur across samples to group contigs into the genome they derived from. This will enable us to reconstruct organism’s genomes. We will then identify genes within these genomes, both taxonomic markers and AMR genes. In this way we will determine exactly which organisms in the environment are acting as reservoirs for AMR. We will place these results into a wider global context by additionally analysing both further metagenome data sets for AMR and by cross-referencing to isolate genome databases for specific organisms.

Training and Skills

CENTA students are required to complete 45 days training throughout their PhD including a 10 day placement. In the first year, students will be trained as a single cohort on environmental science, research methods and core skills. Throughout the PhD, training will progress from core skills sets to master classes specific to the student's projects and themes.

The student will receive extensive training in microbial bioinformatics both metagenomics and genomics. They will learn how to run bioinformatics software for assembly, mapping, gene annotation, phylogenetic tree construction etc. They will gain familiarity with sequence databases such as the ABR and NCBI. They will be taught programming in Python, and C, basic statistics using R and more advanced Bayesian statistical modelling. They will also be given an overview of the molecular biology behind the generation of the data sets, sample preparation and next generation sequencing although the focus of the studentship will be on the bioinformatics and statistics.

Timeline

Year 1: Initial quality control of TMD, assembly, mapping, annotation and contig clustering. Determine the organisms present, their abundances across samples and which possess AMR genes.

Year 2: Search pathogen genome databases e.g. Enterobase for environmental AMR genes. Develop improved algorithms for contig clustering incorporating phylogenetic information.

Year 3: Perform assembly and clustering of additional metagenome databases e.g. HMP and Tara Oceans.

Partners and collaboration (including CASE)

The studentship is a collaboration between Warwick and Exeter universities (Dr Will Gaze). The NERC Centre for Ecology and Hydrology will be a project partner (Dr Andrew Singer). The student will have the opportunity to spend some time visiting Dr Singer to work on integrating the metagenome data into a landscape setting. The bioinformatics training will in part take place through the MRC funded Cloud Infrastructure for Microbial Bioinformatics (CLIMB) consortium (http://www.climb.ac.uk).

Further Details

Dr Christopher Quince (University of Warwick: c.quince@warwick.ac.uk)

Prof. Elizabeth Wellington (University of Warwick: E.M.H.Wellington@warwick.ac.uk)