Halorubrum miltondacostae sp. nov., a potential polyhydroxyalkanoate producer isolated from an inland solar saltern in Rio Maior, Portugal

Abstract

One hundred and sixty-three extreme halophiles were recovered from a single sample collected from an inland solar saltern in Rio Maior. Based on random amplified polymorphic DNA (RAPD) profiles and partial 16S rRNA gene sequencing 125 isolates were identified as members of the Archaea domain within the genus Halorubrum. Two strains, RMP-11^T and RMP-47, showed 99.1 % sequence similarity with the species Halorubrum californiense based on phylogenetic analysis of the 16S rRNA gene sequence. However, phylogenetic analysis based on five housekeeping genes, atpB, EF-2, glnA, ppsA and rpoB’, showed Halorubrum coriense as the closest related species with 96.7 % similarity. The average nucleotide identity (ANI) of strains RMP-11^T, RMP-47 and species Hrr. coriense were within the range of 90.0–90.5 %, supporting that strains RMP-11^T and RMP-47 represent a novel species of the genus Halorubrum. These strains formed red-pigmented colonies that were able to grow in a temperature range of 25–50 °C. Polyhydroxyalkanoate (PHA) granules were detected in both strains. The polar lipid profile was identical to the neutrophilic species of the genus Halorubrum. The Rio Maior sample from which both strains were isolated was metagenome sequenced. We identified five metagenome-assembled genomes representing novel Halorubrum species but distinct from the species represented by strains RMP-11^T and RMP-47. Based on phylogenetic, phylogenomic, comparative genomics, physiological and chemotaxonomic parameters, we describe a new species of the genus Halorubrum represented by strains RMP-11^T (=CECT 30760^T = DSM 115521^T) and RMP-47 (=CECT 30761 = DSM 115541) for which we propose the name Halorubrum miltondacostae sp. nov.