Abstract

An important goal in microbial computational genomics is to identify crucial events in the evolution of a gene that severely alter the duplication, loss, and mobilization patterns of the gene within the genomes in which it disseminates. In this article, we formalize this microbiological goal as a new pattern-matching problem in the domain of gene tree and species tree reconciliation, denoted "Reconciliation-Scenario Altering Mutation (RSAM) Discovery." We propose an [Formula: see text] time algorithm to solve this new problem, wheremandnare the number of vertices of the input gene tree and species tree, respectively, andkis a user-specified parameter that bounds from above the number of optimal solutions of interest. The algorithm first constructs a hypergraph representing thekhighest scoring reconciliation scenarios between the given gene tree and species tree, and then interrogates this hypergraph for subtrees matching a prespecified RSAM pattern. Our algorithm is optimal in the sense that the number of hypernodes in the hypergraph can be lower bounded by [Formula: see text]. We implement the new algorithm as a tool, called RSAM-finder, and demonstrate its application to the identification of RSAMs in toxins and drug resistance elements across a data set spanning hundreds of species.

Highlights

  • Prokaryotes can be found in the most diverse and severe ecological niches of the planet

  • We say that the mutation has a causal association with the observed dissemination pattern of the mutated gene

  • Our hypergraph-ensemble approach is based on a model proposed by [24] for network evolution, where here we extend and adapt it to the DLT model

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Summary

Introduction

Prokaryotes can be found in the most diverse and severe ecological niches of the planet. Our hypergraph-ensemble approach is based on a model proposed by [24] for network evolution, where here we extend and adapt it to the DLT model This hypergraph of k-best reconciliations, intended to provide some robustness to the noise typical of this data, will serve as the search-space for the pattern-matching stage. We adapt the approach proposed by Bansal et al [3] for the basic, one-best variant of DLT reconciliation, extending it to an efficient k-best variant This yields an O(m · n · k) time algorithm for the problem, where m and n are the number of vertices of the input Gene tree and Species tree, respectively, and k is a user-specified parameter that bounds from above the number of optimal solutions of interest. Our tool RSAM-finder provides the users with a query language able to express more robust patterns, according to the various applications where the pattern-search is to be employed

Preliminaries
Hypergraph of k-Best Scenarios
Stage 1
Stage 2
Stage 3
Applications
Methods and Data

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