Rahnella laticis sp. nov. and Rahnella contaminans sp. nov., and emended description of the genus Rahnella

Abstract

Taxonomic positions of six isolates, which were recovered from two different environments in Jeju, Republic of Korea, were examined by a polyphasic analysis. Cells of the isolates were Gram-reaction-negative, facultatively anaerobic, motile and rod-shaped and showed growth at 4–30 °C, pH 4.0–9.0 and with 0–6 (w/v) NaCl. In phylogenomic analysis based on 92 single-copy core genes, it was shown that the isolates belonged to the genus Rahnella and formed three distinct sublines within the genus. The isolates shared 16S rRNA gene sequence similarities of 97.9–100 % with one another. The isolates contained ubiquinone-8 was as the major isoprenoid quinone. The major polar lipids were phosphatidylethanolamine, phosphatidylglycerol and an unidentified aminophospholipid. The predominant fatty acids were C16 : 0 and C17 : 0 cyclo. The G+C content of their genomic DNA was 52.8–53.1 %. Average nucleotide identity and digital DNA–DNA hybridization values supported that strains SAP-17T and Lac-M11T represented two new species of the genus Rahnella , whereas strain SAP-10 was a strain of Rahnella victoriana . Based on the results obtained here, Rahnella laticis sp. nov. (type strain SAP-17T=KCTC 72960T=NBRC 114723T=CCM 9079T) and Rahnella contaminans sp. nov. (type strain Lac-M11T=KACC 21743T=NBRC 114406T) are proposed. Also, an emended description of the genus Rahnella is given on the basis of our physiological and chemotaxonomic results.

Rahnella sp., a Dominant Symbiont of the Core Gut Bacteriome of Dendroctonus Species, Has Metabolic Capacity to Degrade Xylan by Bifunctional Xylanase-Ferulic Acid Esterase

“…Our findings showed that the genome size of Rahnella sp. ChDrAdgB13 is within the range of genomes sizes available for two isolates and 13 species of the genus Rahnella (4.91–5.78 Mbp) ( Fabryová et al, 2018 ; Lee et al, 2020 ; Jeon et al, 2021 ; Brady et al, 2022 ). Among GHs found in this study that might have an ecological role relevant to the nutrition of these bark beetles, families 1, 3, 13, 31, and 43, which have been associated with the hydrolysis of structural and non-structural polysaccharides have specifically been highlighted.…”

A polyphasic taxonomy analysis reveals the presence of an ecotype of Rahnella contaminans associated with the gut of Dendroctonus-bark beetles

“…The genus Rahnella includes species capable of living in diverse aquatic and terrestrial habitats ( Izard et al, 1979 ; Brady et al, 2014 ; Lee et al, 2020 ; Jeon et al, 2021 ; Brady et al, 2022 ), including extremophile environments ( Kumar et al, 2022 ). In this study, a comprehensive attempt to clarify the taxonomic status of Rahnella isolates associated with the gut of Dendroctonus -bark beetles was carried out using phenotypic, molecular, and phylogenetic evidence.…”

“…Rahnella contaminans was isolated and described as a contaminant of refrigerated MRSA agar plates after the isolation of Lactobacillus strains using raw rice wine; however, re-isolation of strains of this species using the same isolation conditions was not possible ( Jeon et al, 2021 ). By contrast, R .…”

“…This result is in agreement with the type of flagellum observed in the ecotype by TEM and with observations made in Rahnella species in other studies, which report the same flagella type ( Izard et al, 1979 ; Brady et al, 2014 , 2022 ; Kumar et al, 2022 ). However, Lee et al (2020) and Jeon et al (2021) reported and showed images of amphitrichous flagella in R . contaminans , R .…”

“…Given that there is a discrepancy between the type of flagella, peritrichous, or amphitrichous (polar), presented by the species of the genus Rahnella ( Jeon et al, 2021 ; Brady et al, 2022 ), observations by TEM of isolates ChDrAdgB13 and JaDmexAd06 were performed to clarify the flagella arrangement of these isolates. In addition, based on the genomes of the 14 taxonomically valid species of Rahnella , we performed a comprehensive in silico analysis of genes encoding flagella.…”