BACKGROUND: Plasmids and viruses are two types of mobile genetic elements (ME), that rely on host cells to reproduce and propagate themselves. Recently, metagenomics has greatly facilitated the discovery and characterization of new plasmids and viruses, which relies on accurate identification of these reads in metagenomes. Some state-of-the-art tools can identify plasmid or viral reads, while others are able to identify the probable host or source species of these reads. Since the Minimizer-based Naïve Bayes Classifier (MNBC) tool accurately classifies chromosomal and viral reads to the species level, we extended it to develop the MNBC-ME tool that can also identify plasmid reads and their putative host species. RESULTS: A standard reference- and test-sequence framework using simulated variable-length reads was used to benchmark MNBC-ME with eleven other state-of-the-art tools for ME identification: DeepMicroClass, geNomad, PPR-Meta, viralVerify, Plasmer, PlasClass, PlasX, VIBRANT, DeepVirFinder, HOTSPOT, and MOSTPLAS. MNBC-ME was the most consistent tool at classifying chromosomal, viral and plasmid reads of variable lengths, in contrast to the other tools whose precision or recall dropped below 50% in some circumstances. MNBC-ME also exceeded 65% and 70% performance in predicting host genus and family of plasmid reads, respectively. CONCLUSIONS: MNBC-ME is tool for identification of both short and long viral- and plasmid-originated reads across a wide variety of read types. It also identifies potential low-level host taxa for plasmid reads, and source taxa for chromosomal and viral reads. It is freely available at https://github.com/ComputationalPathogens/MNBC-ME and can be found as the 'mnbc-me' package in bioconda.

MOTIVATION: State-of-the-art tools for classifying metagenomic sequencing reads provide both rapid and accurate options, although the combination of both in a single tool is a constantly improving area of research. The machine learning-based Naïve Bayes Classifier (NBC) approach provides a theoretical basis for accurate classification of all reads in a sample. RESULTS: We developed the multithreaded Minimizer-based Naïve Bayes Classifier (MNBC) tool to improve the NBC approach by applying minimizers, as well as plurality voting for closely related classification scores. A standard reference- and test-sequence framework using simulated variable-length reads benchmarked MNBC with six other state-of-the-art tools: MetaMaps, Ganon, Kraken2, KrakenUniq, CLARK, and Centrifuge. We also applied MNBC to the "marine" and "strain-madness" short-read metagenomic datasets in the Critical Assessment of Metagenome Interpretation (CAMI) II challenge using a corresponding database from the time. MNBC efficiently identified reads from unknown microorganisms, and exhibited the highest species- and genus-level precision and recall on short reads, as well as the highest species-level precision on long reads. It also achieved the highest accuracy on the "strain-madness" dataset. AVAILABILITY AND IMPLEMENTATION: MNBC is freely available at: https://github.com/ComputationalPathogens/MNBC.

SUMMARY: Whole genome sequencing (WGS) is being adopted in public health for improved surveillance and outbreak analysis. In public health, subtyping has been used to infer phenotypes and distinguish bacterial strain groups. In silico tools that predict subtypes from sequences data are needed to transition historical data to WGS-based protocols. Phylotyper is a novel solution for in silico subtype prediction from gene sequences. Designed for incorporation into WGS pipelines, it is a general prediction tool that can be applied to different subtype schemes. Phylotyper uses phylogeny to model the evolution of the subtype and infer subtypes for unannotated sequences. The phylogenic framework in Phylotyper improves accuracy over approaches based solely on sequence similarity and provides useful contextual feedback. AVAILABILITY AND IMPLEMENTATION: Phylotyper is a python and R package. It is available from: https://github.com/superphy/insilico-subtyping. CONTACT: [email protected]. SUPPLEMENTARY INFORMATION: Supplementary data are available at Bioinformatics online.

BACKGROUND: The pan-genome of a bacterial species consists of a core and an accessory gene pool. The accessory genome is thought to be an important source of genetic variability in bacterial populations and is gained through lateral gene transfer, allowing subpopulations of bacteria to better adapt to specific niches. Low-cost and high-throughput sequencing platforms have created an exponential increase in genome sequence data and an opportunity to study the pan-genomes of many bacterial species. In this study, we describe a new online pan-genome sequence analysis program, Panseq. RESULTS: Panseq was used to identify Escherichia coli O157:H7 and E. coli K-12 genomic islands. Within a population of 60 E. coli O157:H7 strains, the existence of 65 accessory genomic regions identified by Panseq analysis was confirmed by PCR. The accessory genome and binary presence/absence data, and core genome and single nucleotide polymorphisms (SNPs) of six L. monocytogenes strains were extracted with Panseq and hierarchically clustered and visualized. The nucleotide core and binary accessory data were also used to construct maximum parsimony (MP) trees, which were compared to the MP tree generated by multi-locus sequence typing (MLST). The topology of the accessory and core trees was identical but differed from the tree produced using seven MLST loci. The Loci Selector module found the most variable and discriminatory combinations of four loci within a 100 loci set among 10 strains in 1 s, compared to the 449 s required to exhaustively search for all possible combinations; it also found the most discriminatory 20 loci from a 96 loci E. coli O157:H7 SNP dataset. CONCLUSION: Panseq determines the core and accessory regions among a collection of genomic sequences based on user-defined parameters. It readily extracts regions unique to a genome or group of genomes, identifies SNPs within shared core genomic regions, constructs files for use in phylogeny programs based on both the presence/absence of accessory regions and SNPs within core regions and produces a graphical overview of the output. Panseq also includes a loci selector that calculates the most variable and discriminatory loci among sets of accessory loci or core gene SNPs. AVAILABILITY: Panseq is freely available online at http://76.70.11.198/panseq. Panseq is written in Perl.