Two novel Raoultella species associated with bleeding cankers of broadleaf hosts, Raoultella scottia sp. nov. and Raoultella lignicola sp. nov.

Seventeen Gram-negative, facultatively anaerobic bacterial strains were isolated from bleeding cankers of various broadleaf hosts and oak rhizosphere soil in Great Britain. The strains were tentatively identified as belonging to the genus Raoultella based on 16S rRNA gene sequencing. Multilocus sequence analysis (MLSA), based on four protein-encoding genes (fusA, leuS, pyrG, and rpoB), separated the strains into three clusters within the Raoultella genus clade. The majority of strains clustered with the type strain of Raoultella terrigena, with the remaining strains divided into two clusters with no known type strain. Whole genome sequencing comparisons confirmed these two clusters of strains as belonging to two novel Raoultella species which can be differentiated phenotypically from their current closest phylogenetic relatives. Therefore, two novel species are proposed: Raoultella scottia sp. nov. (type strain = BAC 10a-01-01T = LMG 33072T = CCUG 77096T) and Raoultella lignicola sp. nov. (type strain = TW_WC1a.1T = LMG 33073T = CCUG 77094T).

Brenneria tiliae sp. nov., isolated from symptomatic Tilia × moltkei and Tilia × europaea trees in the UK.

Several strains of a previously undescribed bacterial species were isolated from mature Tilia hybrid trees suffering from bleeding cankers at various geographic locations in the UK. The strains were Gram-negative, facultatively anaerobic, and partial sequencing of the gyrB gene revealed that the strains belong to the genus Brenneria with the closest phylogenetic neighbours being Brenneria corticis and Brenneria nigrifluens. Further investigation using a polyphasic approach was undertaken to determine the taxonomic position of the novel species. Phylogenies based on the 16S rRNA gene and multilocus sequence analysis of partial housekeeping gene sequences of gyrB, rpoB, infB and atpD revealed that the strains formed an independent cluster within the genus Brenneria. The phenotypic and chemotaxonomic assays demonstrated that the strains could be differentiated from the closest relatives. Genome analysis of representative strains revealed in silico DNA-DNA hybridization values below the threshold for species delimitation, although the average nucleotide identity values obtained when compared to B. corticis (95.9-96%) were slightly higher than the suggested cut-off value of 95%. However, as all other data suggests that the strains belong to a novel taxon that can be differentiated from the closest relatives, we propose that the strains represent a novel species in the genus Brenneria, Brenneria tiliae sp. nov. (type strain WC1b.1T=LMG 32575T=NCPPB 4697T).

Description of three novel species of Scandinavium: Scandinavium hiltneri sp. nov., Scandinavium manionii sp. nov. and Scandinavium tedordense sp. nov., isolated from the oak rhizosphere and bleeding cankers of broadleaf hosts.

While investigating the bacterial populations of environmental samples taken from a mix of healthy and Acute Oak Decline afflicted Quercus robur (pedunculate or English oak) rhizosphere soil samples and swabs of bleeding lesions on Tilia spp. (lime) and Quercus rubra (red oak) trees, several strains belonging to the order Enterobacterales were isolated using selective media and enrichment broth. Seven strains from the Q. robur rhizosphere, three strains from Tilia spp. and one from Q. rubra were investigated, with their taxonomic status determined via a polyphasic taxonomic approach. Initially stains were identified as potential members of the recently described genus Scandinavium, based on the partial sequencing of three housekeeping genes. Further analysis of phenotypic traits, including fatty acid profiles, coupled with 16S rRNA gene and phylogenomic analysis of whole genome sequences were applied to a subset of the strains. Phylogenetic and phylogenomic analysis repeatedly placed the isolates in a monophyletic clade within Scandinavium, with four distinct clusters observed, one of which corresponded to Scandinavium goeteborgense, the type species of the genus. The remaining three clusters could be phenotypically and genotypically differentiated from each other and S. goeteborgense. As such, we describe three novel species of the genus, for which we propose the names Scandinavium hiltneri sp. nov. (type strain H11S7T = LMG 32612T = CCUG 76179T), Scandinavium manionii sp. nov. (type strain H17S15T = LMG 32613T = CCUG 76183T) and Scandinavium tedordense sp. nov. (type strain TWS1aT = LMG 32614T = CCUG 76188T). Additionally, the descriptions of the genus Scandinavium and the type species, S. goeteborgense, are emended.