Characterization of Martelella soudanensis sp. nov., Isolated from a Mine Sediment

Abstract

Gram-stain-negative, strictly aerobic, non-spore-forming, non-motile, and rod-shaped bacterial strains, designated NC18T and NC20, were isolated from the sediment near-vertical borehole effluent originating 714 m below the subsurface located in the Soudan Iron Mine in Minnesota, USA. The 16S rRNA gene sequence showed that strains NC18T and NC20 grouped with members of the genus Martelella, including M. mediterranea DSM 17316T and M. limonii YC7034T. The genome sizes and G + C content of both NC18T and NC20 were 6.1 Mb and 61.8 mol%, respectively. Average nucleotide identity (ANI), the average amino acid identity (AAI), and digital DNA–DNA hybridization (dDDH) values were below the species delineation threshold. Pan-genomic analysis showed that NC18T, NC20, M. mediterranea DSM 17316T, M. endophytica YC6887T, and M. lutilitoris GH2-6T had 8470 pan-genome orthologous groups (POGs) in total. Five Martelella strains shared 2258 POG core, which were mainly associated with amino acid transport and metabolism, general function prediction only, carbohydrate transport and metabolism, translation, ribosomal structure and biogenesis, and transcription. The two novel strains had major fatty acids (>5%) including summed feature 8 (C18:1 ω7c and/or C18:1 ω6c), C19:0 cyclo ω8c, C16:0, C18:1 ω7c 11-methyl, C18:0, and summed feature 2 (C12:0 aldehyde and/or iso-C16:1 I and/or C14:0 3-OH). The sole respiratory quinone was uniquinone-10 (Q-10). On the basis of polyphasic taxonomic analyses, strains NC18T and NC20 represent novel species of the genus Martelella, for which the name Martelella soudanensis sp. nov. is proposed. The type strain is NC18T (=KTCT 82174T = NBRC 114661T).

Genomic Analysis of Halotolerant Bacterial Strains Martelella soudanensis NC18T and NC20

“…The 16S rRNA gene sequences of M. soudanensis NC18 T and NC20 showed 100% similarity. Comparative 16S rRNA gene sequence analyses revealed that M. soudanensis NC18 T and NC20 were most closely related to M. mediterranea DSM 17316 T (99.0%), Martelella limonii YC7034 T (98.6%), M. endophytica YC6887 T (98.1%), Martelella mangrovi BM9-1 T (97.9%), M. lutilitoris GH2-6 T (97.9%), Martelella radicis BM5-7 T (97.6%), Martelella suaedae YC7033 T (97.6%), and M. caricis GH2-8 T (97.2%) [ 16 ]. The neighbor-joining, maximum-likelihood, and maximum-parsimony phylogenetic analyses revealed that the two isolates formed a lineage within the clade of the genus Martelella but are separate from the clade constituted of the species M. mediterranea and M. limonii ( Figs.…”

“…1 , S1 ). The ANI and dDDH values between strains NC18 T and NC20 were 99.9% and 100%, respectively [ 16 ]. These results revealed that the two strains belonged to a single species.…”

“…In the KEGG analysis, carbohydrate and amino acid metabolism were mainly abundant, indicating that M. soudanensis is capable of using a variety of carbon sources ( Fig. 2A , Table S1 ) [ 16 ]. In particular, genes related to membrane transport and signal transduction were ranked high, suggesting a higher tolerance level of Martelella under harsh salt conditions.…”

“…The halophiles M. soudanensis NC18 T and NC20 were isolated from Soudan Underground Mine State Park in Soudan, Minnesota, USA [ 16 ]. Genomic DNA was extracted and purified using an AccuPrep Genomic DNA Extraction Kit (Bioneer, Korea) according to the manufacturer’s instructions.…”

“…Martelella soudanensis NC18 T and NC20 were isolated from a sediment sample collected from borehole effluent originating 714 m below the subsurface at the Soudan Iron Mine in northern Minnesota, USA. Based on the results of phylogenetic and genomic analyses, these two isolates clearly formed a phylogenic lineage with members of the genus Martelella [ 16 ]. However, these strains could also be clearly distinguished from other closely related genera based on their ability to grow at higher salt concentration.…”