Durán-Viseras Ana, Sánchez-Porro Cristina, Ventosa Antonio
Department of Microbiology and Parasitology, Faculty of Pharmacy, University of Sevilla, Sevilla, Spain.
Front Microbiol. 2021 Nov 4;12:751746. doi: 10.3389/fmicb.2021.751746. eCollection 2021.
Metagenomic studies on prokaryotic diversity of hypersaline soils from the Odiel saltmarshes, South-west Spain, revealed a high proportion of genomic sequences not related to previously cultivated taxa, that might be related to haloarchaea with a high environmental and nutritional flexibility. In this study, we used a culturomics approach in order to isolate new haloarchaeal microorganisms from these hypersaline soils. Four haloarchaeal strains, designated strains F24A, F28, F27, and F13, phylogenetically related to the genus , were isolated and characterized in detail. The phylogenomic tree based on the 100 orthologous single-copy genes present in the genomes of these four strains as well as those of the type strains of the species CECT 7537, JCM 18369 and JCM 18640, that were determined in this study, revealed that these four new isolates clustered on three groups, with strains F24A and F28 within a single cluster, and altogether with the species of . Additionally, Orthologous Average Nucleotide Identity (OrthoANI), digital DNA-DNA hybridization (dDDH) and Average Amino-acid Identity (AAI) values, likewise phenotypic characteristics, including their polar lipids profiles, permitted to determine that they represent three new species, for which we propose the names sp. nov. (type strain F13), sp. nov. (type strain F27) and sp. nov. (type strain F24A). An in deep comparative genomic analysis of species of the genus , including their metabolism, their capability to biosynthesize secondary metabolites and their osmoregulatory adaptation mechanisms was carried out. Although they use a strategy, the identification of the complete pathways for the biosynthesis of the compatible solutes trehalose and glycine betaine, not identified before in any other haloarchaea, might suggest alternative osmoadaptation strategies for this group. This alternative osmoregulatory mechanism would allow this group of haloarchaea to be versatile and eco-physiologically successful in hypersaline environments and would justify the capability of the species of this genus to grow not only on environments with high salt concentrations [up to 30% (w/v) salts], but also under intermediate to low salinities.
对西班牙西南部奥迪尔盐沼高盐土壤中细菌多样性的宏基因组研究表明，很大一部分基因组序列与先前培养的分类群无关，这些序列可能与具有高度环境和营养适应性的嗜盐古菌有关。在本研究中，我们采用培养组学方法从这些高盐土壤中分离新的嗜盐古菌微生物。分离并详细鉴定了四株嗜盐古菌菌株，分别命名为F24A、F28、F27和F13，它们在系统发育上与该属相关。基于这四株菌株以及本研究中测定的CECT 7537、JCM 18369和JCM 18640物种模式菌株基因组中存在的100个直系单拷贝基因构建的系统发育树表明，这四个新分离株聚为三组，F24A和F28菌株在同一簇中，并且与该属的物种聚在一起。此外，直系平均核苷酸同一性（OrthoANI）、数字DNA-DNA杂交（dDDH）和平均氨基酸同一性（AAI）值，以及包括其极性脂质谱在内的表型特征，都表明它们代表三个新物种，我们为此提出了新物种的名称：新种（模式菌株F13）、新种（模式菌株F27）和新种（模式菌株F24A）。对该属物种进行了深入的比较基因组分析，包括它们的代谢、生物合成次生代谢物的能力以及渗透调节适应机制。尽管它们采用一种策略，但在任何其他嗜盐古菌中均未发现的相容性溶质海藻糖和甘氨酸甜菜碱生物合成完整途径的鉴定，可能暗示了该类群的替代渗透适应策略。这种替代渗透调节机制将使这组嗜盐古菌在高盐环境中具有多功能性和生态生理学上的成功，并证明该属物种不仅能够在高盐浓度[高达30%（w/v）盐]的环境中生长，而且能够在中低盐度环境下生长的能力。
