Global diversity of enterococci and description of 18 novel species

zol & fai: large-scale targeted detection and evolutionary investigation of gene clusters

Many universally and conditionally important genes are genomically aggregated within clusters. Here, we introduce fai and zol, which together enable large-scale comparative analysis of different types of gene clusters and mobile-genetic elements (MGEs), such as biosynthetic gene clusters (BGCs) or viruses. Fundamentally, they overcome a current bottleneck to reliably perform comprehensive orthology inference at large scale across broad taxonomic contexts and thousands of genomes. First, fai allows the identification of orthologous instances of a query gene cluster of interest amongst a database of target genomes. Subsequently, zol enables reliable, context-specific inference of ortholog groups for individual protein-encoding genes across gene cluster instances. In addition, zol performs functional annotation and computes a variety of evolutionary statistics for each inferred ortholog group. Importantly, in comparison to tools for visual exploration of homologous relationships between gene clusters, zol can scale to thousands of gene cluster instances and produce detailed reports that are easy to digest. To showcase fai and zol, we apply them for: (i) longitudinal tracking of a virus in metagenomes, (ii) discovering novel population-level genetic insights of two common BGCs in the fungal species Aspergillus flavus, and (iii) uncovering large-scale evolutionary trends of a virulence-associated gene cluster across thousands of genomes from a diverse bacterial genus.

Enterococcus montenegrensis sp. nov., isolated from artisanal Montenegrin dry sausage

A novel, Gram-positive, facultative anaerobe, coccoid and non-motile bacterium, designated as CoE-012-22T was isolated from dried beef sausage (the original name in Montenegro is Govedji Kulen) manufactured in the municipality of Rozaje (Montenegro) in 2021. Cells of this strain were oxidase- and catalase-negative. Growth occurred at 4-50 °C, at pH 5.0-8.0 and with 0-6.5 % (w/v) NaCl in diverse growth media. MALDI-TOF analysis identified the strain as Enterococcus canintestini (log score 2). Phylogenetic analysis of the 16S rRNA gene and whole genome sequences assigned the strain to the genus Enterococcus. The closest relatives were E. canintestini DSM 21207T and E. dispar ATCC 51266T with 16S rRNA gene sequence pairwise similarities of 99.34 and 98.59 %, respectively. The average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values between isolate CoE-012-22T and other enterococci species were below the thresholds for species delineation thresholds (95.0 % ANI; 70.0 % dDDH) with maximum identities of 84.13 % (ANIb), 86.43 % (ANIm) and 28.4 % (dDDH) to E. saigonensis JCM 31193T and 70.97 % (ANIb), 88.99 % (ANIm) and 32.4 % (dDDH) to E. malodoratus ATCC 43197T. Two unknown Enterococcus isolates, Enterococcus sp. MJM12 and Enterococcus SMC-9, showed identities of 99.87 and 99.94 % (16S rRNA), 98.57 and 98.65 % (ANIb), 98.93 and 99.02 % (ANIm), and 89.8 and 90.0 % (dDDH) to strain CoE-012-22T and can therefore be regarded as the same species. Based on the characterization results, strain CoE-012-22T was considered to represent a novel species, for which the name Enterococcus montenegrensis sp. nov. is proposed. The type strain is CoE-012-22T (=DSM 115843T=NCIMB 15468T).