Phylogenomic analyses of the Listeriaceae family support species reclassification and proposal of a new family and new genera.

The taxonomy of the Listeriaceae family has undergone substantial revisions, expanding the Listeria genus from 6 to 29 species since 2009. However, these classifications have relied on 16S rRNA gene sequences and conventional polyphasic taxonomy, with limited use of genomic approaches. This study aimed to employ genomic tools, including phylogenomics, Overall Genomic Relatedness Indices (OGRIs), and core-genome phylogenomic analyses, to reevaluate the taxonomy of the Listeriaceae family. The analyses involved the construction of phylogenetic and phylogenomic trees based on 16S rRNA gene sequences and core genomes from 34 type strain genomes belonging to Listeriaceae family. OGRIs, which encompass Average Amino acid Identity (AAI), core-proteome AAI (cAAI), and Percentage of Conserved Proteins (POCP), were calculated, and specific threshold values of 70%, 87%, and 72-73% were established, respectively, to delimitate genera in the Listeriaceae family. These newly proposed OGRI thresholds unveiled distinct evolutionary lineages. The outcomes of this taxonomic re-evaluation were: (i): the division of the Listeria genus into an emended Listeria genus regrouping only Listeria senso stricto species; (ii): the remaining Listeria senso lato species were transferred into three newly proposed genera: Murraya gen. nov., Mesolisteria gen. nov., and Paenilisteria gen. nov. within Listeriaceae; (iii): Brochothrix was transferred to the newly proposed family Brochothricaceae fam. nov. within the Caryophanales order; (iiii): Listeria ivanovii subsp. londonensis was elevated to the species level as Listeria londonensis sp. nov.; and (iiiii): Murraya murrayi comb. nov. was reclassified as a later heterotypic synonym of Murraya grayi comb. nov. This taxonomic framework enables more precise identification of pathogenic Listeriaceae species, with significant implications for important areas such as food safety, clinical diagnostics, epidemiology, and public health.

Phylogenomic Analysis Supports the Reclassification of Caldicoprobacter faecalis (Winter et al. 1988) Bouanane-Darenfed et al. (2015) as a Later Heterotypic Synonym of Caldicoprobacter oshimai Yokoyama et al. (2010).

This study employs genome-based methodologies to explore the taxonomic relationship between Caldicoprobacter faecalis DSM 20678T and Caldicoprobacter oshimai DSM 21659T. The genome-based similarity indices calculations consisting of digital DNA-DNA Hybridization (dDDH), Average Amino Aid Identity (AAI), and Average Nucleotide Identity (ANI) between the genomes of these two type strains yielded percentages of 91.2%, 98.9%, and 99.1%, respectively. These values were above the recommended thresholds of 70% (dDDH) and 95-96% (ANI and AAI) for bacterial species delineation, indicating a shared taxonomic position for C. faecalis and C. oshimai. Furthermore, analysis utilizing the 'Bacterial Pan Genome Analysis' (BPGA) pipeline and constructing a Maximum Likelihood core-genes tree using FastTree2 consistently demonstrated the close relationship between C. faecalis DSM 20678T and C. oshimai DSM 21659T, evident from their clustering in the core-genes phylogenomic tree. Based on these comprehensive findings, we propose the reclassification of C. faecalis as a later heterotypic synonym of C. oshimai.

Genome-based reclassification of Kitasatospora niigatensis as a later heterotypic synonym of Kitasatospora cineracea Tajima et al. (2001).

The present study used genome-based approaches to investigate the taxonomic relationship between Kitasatospora cineracea DSM 44780T and Kitasatospora niigatensis DSM 44781T, two species that were previously described by Tajima et al. (Int J Syst Evol Microbiol 51:1765-1771, 2001). The digital DNA-DNA hybridization (dDDH), average amino acid identity (AAI), and average nucleotide identity (ANI) values between the genomes of the two type strains were 90.3, 98.7, and 99.1%, respectively. These values exceeded the established thresholds of 70% (dDDH) and 95-96% (ANI and AAI) for bacterial species delineation, suggesting that K. cineracea and K. niigatensis should share the same taxonomic position. Furthermore, our analysis using the 'Bacterial Pan Genome Analysis' (BPGA) pipeline and the Maximum Likelihood core-genes tree inferred using FastTree2 consistently demonstrated that K. cineracea DSM 44780T and K. niigatensis DSM 44781T are closely related, as indicated by the clustering of these strains in the core-genes phylogenomic tree. Based on these findings, we propose that K. niigatensis should be considered a later heterotypic synonym of K. cineracea.

Saccharothrix ghardaiensis sp. nov., an actinobacterium isolated from Saharan soil.

The taxonomic position of a new Saccharothrix strain, designated MB46T, isolated from a Saharan soil sample collected in Mzab region (Ghardaïa province, South Algeria) was established following a polyphasic approach. The novel microorganism has morphological and chemical characteristics typical of the members of the genus Saccharothrix and formed a phyletic line at the periphery of the Saccharothrix espanaensis subcluster in the 16S rRNA gene dendrograms. Results of the 16S rRNA gene sequence comparisons revealed that strain MB46T shares high degrees of similarity with S. espanaensis DSM 44229T (99.2%), Saccharothrix variisporea DSM 43911T (98.7%) and Saccharothrix texasensis NRRL B-16134T (98.6%). However, the new strain exhibited only 12.5-17.5% DNA relatedness to the neighbouring Saccharothrix spp. On the basis of phenotypic characteristics, 16S rRNA gene sequence comparisons and DNA-DNA hybridizations, strain MB46T is concluded to represent a novel species of the genus Saccharothrix, for which the name Saccharothrix ghardaiensis sp. nov. (type strain MB46T = DSM 46886T = CECT 9046T) is proposed.

Planomonospora algeriensis sp. nov., an actinobacterium isolated from a Saharan soil of Algeria.

A filamentous actinobacterium, designated strain PM3T, was isolated from a Saharan soil sample collected from Béni-Abbès, Béchar (South-West Algeria). A polyphasic taxonomic study was carried out to establish the status of strain PM3T. The isolate was found to have morphological and chemotaxonomical properties associated with members of the genus Planomonospora. The new isolated microorganism developed cylindrical sporangia arranged in double parallel rows on aerial mycelium, each one containing a motile single sporangiospore. The cell wall of the strain was found to contain meso-diaminopimelic acid. Whole-cell hydrolysates were found to contain madurose, glucose, mannose and ribose. The predominant menaquinone was identified as MK-9(H2) (69.6%). The polar lipids detected were identified as diphosphatidylglycerol, phosphatidylglycerol, phosphatidylinositol, phosphatidylethanolamine, phosphatidylhydroxyethanolamine and glucosamine-containing lipids. The major fatty acids were found to be C17:1ω9c (38.6%) and C17:0 (24.2%). Results of 16S rRNA gene sequence comparison revealed that strain PM3T shared a high degree of 16S rRNA gene sequence similarity with Planomonospora sphaerica DSM 44632T (99.3%), Planomonospora parontospora subsp. parontospora DSM 43177T (99.2%) and P. parontospora subsp. antibiotica DSM 43869T (99.0%). DNA-DNA hybridization values between strain PM3T and the type strains of the closely related species were between 58.4 and 70.1%. The combination of phylogenetic analysis, DNA-DNA relatedness data, phenotypic characteristics and chemotaxonomic data support the conclusion that strain PM3T represents a novel species of the genus Planomonospora, for which the name Planomonospora algeriensis sp. nov. is proposed. The type strain is PM3T (=DSM 46752T = CECT 9047T).

Actinophytocola algeriensis sp. nov., an actinobacterium isolated from Saharan soil.

During our investigations of new actinobacterial taxa, a novel actinobacterial strain, designated MB20T, was isolated from a Saharan soil sample, collected in the Mzab region (Ghardaïa province, southern Algeria). In order to reveal its taxonomic position, the novel strain was characterized following a polyphasic taxonomic approach. It was noticed that strain MB20T produced white, branched and fragmented substrate mycelium with no aerial mycelium on most of the media tested. Chemotaxonomic and phylogenetic studies clearly demonstrated that strain MB20T belonged to the family Pseudonocardiaceae and was closely related to the genus Actinophytocola. Cell-wall hydrolysates contained meso-diaminopimelic acid but not glycine, and whole-cell hydrolysates contained galactose, glucose and ribose. The diagnostic phospholipid was phosphatidylethanolamine. Mycolic acids were not detected while the predominant fatty acid was found to be iso-branched hexadecanoate (iso-C16 : 0). The major menaquinone was MK-9(H4). Results of the 16S rRNA gene sequence comparison revealed that strain MB20T shared the highest degree of similarity with Actinophytocola gilvus DSM 45828T (98.5 %), Actinophytocola corallina DSM 45659T (98.0 %) and Actinophytocola timorensis DSM 45660T (97.5 %). However, DNA-DNA hybridization studies showed only 32.9 % similarity with A. timorensis, 23.7 % similarity with A. gilvus and 17.9 % similarity with A. corallina. On the basis of phenotypic characteristics, 16S rRNA gene sequence comparisons and DNA-DNA hybridization, strain MB20T was revealed to be a representative of a novel species of the genus Actinophytocola, for which the name Actinophytocola algeriensis sp. nov. (type strain MB20T =DSM 46746T =CECT 8960T) is proposed.

Saccharothrix isguenensis sp. nov., an actinobacterium isolated from desert soil.

A novel actinobacterial strain, designated MB27T, was isolated from a Saharan soil sample collected in Mzab region (Ghardaïa province, South Algeria). Strain MB27T was characterized following a polyphasic taxonomic approach. This strain produced a branched and fragmented substrate mycelium, which was found to have a yellowish orange colour. A white scanty aerial mycelium was produced on most media tested. Chemotaxonomic and phylogenetic studies clearly demonstrated that strain MB27T belongs to the family Pseudonocardiaceae and is closely related to the genus Saccharothrix. Cell-wall hydrolysates contained meso-diaminopimelic acid but not glycine, and whole-cell hydrolysates contained galactose, glucose, ribose and small amounts of mannose and rhamnose. The detected phospholipids were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylmethylethanolamine, phosphatidylethanolamine, phosphatidylinositol and phosphatidylinositol mannosides. Mycolic acids were not detected while the predominant fatty acid was iso-branched hexadecanoate (iso-C16 : 0). The major menaquinone was MK-9(H4). Results of 16S rRNA gene sequence comparisons revealed that strain MB27T shairs the highest degree of similarity with Saccharothrix ecbatanensis DSM 45486T (99.8%), Saccharothrix hoggarensis DSM 45457T (99.3 %), Saccharothrix longispora DSM 43749T (98.6 %) and Saccharothrix yanglingensis DSM 45665T (98.6 %). However, it exhibited only 11-42 % DNA-DNA relatedness to the neighbouring Saccharothrixspecies. On the basis of phenotypic characteristics, 16S rRNA gene sequence comparisons and DNA-DNA hybridization, strain MB27T is shown to represent a novel species of the genus Saccharothrix, for which the name Saccharothrix isguenensis sp. nov. (type strain MB27T=DSM 46885T=CECT 9045T) is proposed.