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 Actinopolyspora righensis Meklat et al. 2013 as a later heterotypic synonym of Actinopolyspora lacussalsi Guan et al. 2013 and description of Actinopolyspora lacussalsi subsp. lacussalsi subsp. nov. and Actinopolyspora lacussalsi subsp. righensis subsp. nov.

A genome led phylophasic study was designed to determine the taxonomic status of a strain, DSM 45956, recovered from a Saharan desert soil. A wealth of taxonomic data, including average nucleotide identity and DNA:DNA hybridization (DDH) values, showed that the isolate and the type strains of Actinopolyspora lacussalsi and Actinopolyspora righensis belong to the same species. Consequently, it is proposed that A. righensis is a heterotypic synonym of A. lacussalsi. Similarly, DDH values and associated phenotypic data show that A. lacussalsi contains two subspecies, A. lacussalsi subsp. lacussalsi and A. lacussalsi subsp. righensis which includes isolate DSM 45956.

Reclassification of Mzabimyces algeriensis Saker et al. 2015 as Halopolyspora algeriensis comb. nov.

Halopolyspora alba AFM10251T was proposed to represent a novel species of a new genus belonging to the family Actinopolysporaceae in a previous study. The family Mzabimycetaceae , containing one genus, Mzabimyces, was proposed subsequently and Mzabimyces algeriensis H195T was the type strain. However, analysis of 16S rRNA gene sequence similarity showed that the two strains were highly similar (99.2 %). Phenotypic and chemotaxonomic data, as well as DNA-DNA hybridization confirmed that the two strains are different genomic species of the same genus, Halopolyspora. Mzabimyces algeriensis should be classified in the genus Halopolyspora as Halopolysporaalgeriensis comb. nov. The type strain of Halopolysporaalgeriensis is H195T (=DSM 46680T=CECT 8575T).

Prauserella isguenensis sp. nov., a halophilic actinomycete isolated from desert soil.

Two actinomycete strains, designated H225(T) and H137, were isolated from two soil samples collected from the arid region of Ahbas at Béni-Isguen (Mzab), located in the Algerian Sahara. Phylogenetic analyses based on 16S rRNA gene sequences indicated that the novel strains should be assigned to the genus Prauserella of the family Pseudonocardiaceae , and they were therefore subjected to a polyphasic taxonomic study. These two strains contained meso-diaminopimelic acid as the diagnostic diamino acid and arabinose and galactose as major whole-cell sugars. The diagnostic phospholipid was phosphatidylethanolamine. The predominant menaquinone was MK-9(H4), and the major fatty acid was iso-C16 : 0. DNA-DNA hybridization values between strain H225(T) and its closest phylogenetic neighbours, namely Prauserella flava DSM 45265(T), Prauserella alba DSM 44590(T), Prauserella aidingensis DSM 45266(T), Prauserella salsuginis DSM 45264(T) and Prauserella sediminis DSM 45267(T), were clearly below the 70% threshold used for species delineation. The genomic DNA G+C content of strains H225(T) and H137 was 70.4 mol%. On the basis of phenotypic and genotypic data, strains H225(T) and H137(T) are considered to represent a novel species of the genus Prauserella , for which the name Prauserella isguenensis sp. nov. is proposed. The type strain is H225(T) ( =DSM 46664(T) = CECT 8577(T)).

Actinopolyspora biskrensis sp. nov., a novel halophilic actinomycete isolated from Northern Sahara.

A novel halophilic, filamentous actinomycete, designated H254(T), was isolated from a Saharan soil sample collected from Biskra (Northern Sahara), and subjected to a polyphasic taxonomic characterization. The strain is Gram-positive, aerobic, and halophilic, and the optimum NaCl concentration for growth is 15-20 % (w/v). The cell-wall hydrolysate contained meso-diaminopimelic acid, and the diagnostic whole-cell sugars were arabinose and galactose. The diagnostic phospholipid detected was phosphatidylcholine, and MK-9(H4) was the predominant menaquinone. The major fatty acid profiles were anteiso-C17:0 (32.8 %), C15:0 (28 %), and iso-C17:0 (12.3 %). Comparative analysis of the 16S rRNA gene sequences revealed that the strain H254(T) formed a well-separated sub-branch within the radiation of the genus Actinopolyspora, and the microorganism was most closely related to Actinopolyspora saharensis DSM 45459(T) (99.2 %), Actinopolyspora halophila DSM 43834(T) (99.1 %), and Actinopolyspora algeriensis DSM 45476(T) (99.0 %). Nevertheless, the strain had relatively lower mean values for DNA-DNA relatedness with the above strains (57.2, 68.4, and 45.6 %, respectively). Based on phenotypic features and phylogenetic position, we propose that strain H254(T) represents a novel species of the genus Actinopolyspora, for which the name Actinopolyspora biskrensis sp. nov. is proposed. The type strain of A. biskrensis is strain H254(T) (=DSM 46684(T) =CECT 8576(T)).

Mzabimyces algeriensis gen. nov., sp. nov., a halophilic filamentous actinobacterium isolated from a Saharan soil, and proposal of Mzabimycetaceae fam. nov.

Three halophilic mycelium-forming actinobacteria, strains H195(T), H150 and H151, were isolated from a Saharan soil sample collected from Béni-isguen in the Mzab region (Ghardaïa, South of Algeria) and subjected to a polyphasic taxonomic characterisation. These strains were observed to show an aerial mycelium differentiated into coccoid spore chains and fragmented substrate mycelium. Comparative analysis of the 16S rRNA gene sequences revealed that the highest sequence similarities were to Saccharopolyspora qijiaojingensis YIM 91168(T) (92.02 % to H195(T)). Phylogenetic analyses showed that the strains H195(T), H150 and H151 represent a distinct phylogenetic lineage. The cell-wall hydrolysate was found to contain meso-diaminopimelic acid, and the diagnostic whole-cell sugars were identified as arabinose and galactose. The major cellular fatty acids were identified as iso-C15:0, iso-C16:0, iso-C17:0 and anteiso-C17:0. The diagnostic phospholipid detected was phosphatidylcholine and MK-9 (H4) was found to be the predominant menaquinone. The genomic DNA G+C content of strain H195(T) was 68.2 mol%. On the basis of its phenotypic features and phylogenetic position, we propose that strain H195(T) represents a novel genus and species, Mzabimyces algeriensis gen. nov., sp. nov., within a new family, Mzabimycetaceae fam. nov. The type strain of M. algeriensis is strain H195(T) (=DSM 46680(T) = MTCC 12101(T)).