SPRISS: Approximating Frequent $k$-mers by Sampling Reads, and Applications

TL;DR

SPRISS is an efficient sampling-based algorithm that approximates frequent $k$-mers in large sequencing datasets, significantly reducing computational time while maintaining accuracy for various genomic analyses.

Contribution

It introduces a simple sampling scheme combined with existing $k$-mer counting methods to efficiently approximate frequent $k$-mers in large datasets.

Findings

SPRISS achieves high accuracy in approximating frequent $k$-mers.

It reduces analysis time by a significant margin.

Effective in metagenomic dataset comparison and discriminative $k$-mer identification.

Abstract

The extraction of $k$-mers is a fundamental component in many complex analyses of large next-generation sequencing datasets, including reads classification in genomics and the characterization of RNA-seq datasets. The extraction of all $k$-mers and their frequencies is extremely demanding in terms of running time and memory, owing to the size of the data and to the exponential number of $k$-mers to be considered. However, in several applications, only frequent $k$-mers, which are $k$-mers appearing in a relatively high proportion of the data, are required by the analysis. In this work we present SPRISS, a new efficient algorithm to approximate frequent $k$-mers and their frequencies in next-generation sequencing data. SPRISS employs a simple yet powerful reads sampling scheme, which allows to extract a representative subset of the dataset that can be used, in combination with any $k$-mer counting algorithm, to perform downstream analyses in a fraction of the time required by the analysis of the whole data, while obtaining comparable answers. Our extensive experimental evaluation demonstrates the efficiency and accuracy of SPRISS in approximating frequent $k$-mers, and shows that it can be used in various scenarios, such as the comparison of metagenomic datasets and the identification of discriminative $k$-mers, to extract insights in a fraction of the time required by the analysis of the whole dataset.