Leeia oryzae gen. nov., sp. nov., isolated from a rice field in Korea

Phylogenomics and molecular signatures support division of the order Neisseriales into emended families Neisseriaceae and Chromobacteriaceae and three new families Aquaspirillaceae fam. nov., Chitinibacteraceae fam. nov., and Leeiaceae fam. nov

The order Neisseriales contains 37 genera harboring 122 species with validly published names, which are placed into two families, Neisseriaceae and Chromobacteriaceae. Genome sequences are now available for 35 of the 37 Neisseriales genera for reliably determining their evolutionary relationships and taxonomy. We report here comprehensive phylogenomic and comparative analyses on protein sequences from 110 Neisseriales genomes plus 3 Chitinimonas genomes using multiple approaches. In a phylogenomic tree based on 596 core proteins, Neisseriales species formed 5 strongly supported clades. In addition to the clades for Neisseriaceae and Chromobacteriaceae families, three novel species clades designated as the "Chitinibacteraceae", "Aquaspirillaceae", and "Leeiaceae" were observed. The genus Chitinimonas grouped reliably with members of the "Chitinibacteraceae" clade. The major clades within the order Neisseriales can also be distinguished based on average amino acid identity analysis. In parallel, our comparative genomic studies have identified 30 conserved signature indels (CSIs) that are specific for members of the order Neisseriales or its five main clades. One of these CSIs is uniquely shared by all Neisseriales, whereas 8, 4, 9, 3 and 5 CSIs are distinctive characteristics of the Neisseriaceae, Chromobacteriaceae, "Chitinibacteraceae", "Aquaspirillaceae" and "Leeiaceae" clades, respectively. Based on the strong phylogenetic and molecular evidence presented here, we are proposing that the three newly identified clades should be recognized as novel families (Chitinibacteraceae fam. nov., Aquaspirillaceae fam. nov. and Leeiaceae fam. nov.) within the order Neisseriales. In addition, we are also emending descriptions of the families Neisseriaceae and Chromobacteriaceae regarding their constituent genera and other distinguishing characteristics.

Leeia aquatica sp. nov., isolated from freshwater

A Gram-stain-negative, rod-shaped, obligately aerobic, motile by a single polar flagellum, chemoheterotrophic bacterium, designated strain IMCC25680^T, was isolated from surface water in Chungju Lake, Republic of Korea. 16S rRNA gene sequence analysis revealed that strain IMCC25680^T was most closely related to Leeia oryzae HW7^T with 95.5% sequence similarity and formed a robust clade with L. oryzae HW7^T. Whole genome sequencing showed that strain IMCC25680^T had a genome 3.6 Mbp long with 60.7 mol% DNA G+C content. Average nucleotide identity and digital DNA-DNA hybridization values between strain IMCC25680^T and L. oryzae HW7^T were 72.4% and 18.5%, respectively, indicating that the novel strain represents a novel species of the genus Leeia. The major cellular fatty acids of strain IMCC25680^T were iso-C_16:0 and summed feature 3 (comprising C_16:1 ω6c and/or C_16:1 ω7c). The respiratory quinone detected in the strain was ubiquinone-8. The major polar lipids were found to be phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol and two unidentified polar lipids. On the basis of the phylogenetic and phenotypic characterization, strain IMCC25680^T was considered to represent a novel species within the genus Leeia, for which the name Leeia aquatica sp. nov. is proposed. The type strain is IMCC25680^T (=KACC 19487^T =NBRC 113132^T).

Rivicola pingtungensis gen. nov., sp. nov., a new member of the family Neisseriaceae isolated from a freshwater river

A bacterial strain, designated Npb-03(T), was isolated from a freshwater river in Taiwan and was characterized using a polyphasic taxonomic approach. The cells were Gram-reaction-negative, straight rod-shaped, non-motile, non-spore-forming and facultatively anaerobic. Growth occurred at 10-37 °C (optimum, 30-35 °C), at pH 6.0-8.0 (optimum, pH 6.0-7.0) and with 0-1.0% NaCl (optimum, 0%). The predominant fatty acids were summed feature 3 (comprising C(16 : 1)ω7c and/or C(16 : 1)ω6c) and C(16 : 0). The major isoprenoid quinone was Q-8 and the DNA G+C content was 64.1 mol%. The polar lipid profile consisted of a mixture of phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol, an uncharacterized aminolipid and three uncharacterized phospholipids. The major polyamines were putrescine, 2-hydroxyputrescine, cadaverine and spermidine. Phylogenetic analyses based on 16S rRNA gene sequences showed that strain Npb-03(T) forms a distinct lineage with respect to closely related genera within the family Neisseriaceae of the class Betaproteobacteria, most closely related to the genera Aquaspirillum, Laribacter, Leeia and Microvirgula, and the levels of 16S rRNA gene sequence similarity with respect to the type species of related genera are less than 93%. On the basis of the genotypic and phenotypic data, strain Npb-03(T) represents a novel genus and species of the family Neisseriaceae, for which the name Rivicola pingtungensis gen. nov., sp. nov. is proposed. The type strain is Npb-03(T) ( = BCRC 80376(T) = LMG 26668(T) = KCTC 23712(T)).

Phylogenomics and molecular signatures for the order Neisseriales: proposal for division of the order Neisseriales into the emended family Neisseriaceae and Chromobacteriaceae fam. nov

The species from the order Neisseriales are currently distinguished from other bacteria on the basis of branching in 16S rRNA gene trees. For this order containing a single family, Neisseriaceae, no distinctive molecular, biochemical, or phenotypic characters are presently known. We report here detailed phylogenetic and comparative analyses on the 27 genome sequenced species of the order Neisseriales. Our comparative genomic analyses have identified 54 conserved signature indels (CSIs) in widely distributed proteins that are specific for either all of the sequenced Neisseriales species or a number of clades within this order that are also supported by phylogenetic analyses. Of these CSIs, 11 are specifically present in all of the sequenced species from this order, but are not found in homologous proteins from any other bacteria. These CSIs provide novel molecular markers specific for, and delimiting, this order. Twenty-one CSIs in diverse proteins are specific for a group comprised of the genera Neisseria, Eikenella, Kingella, and Simonsiella (Clade I), which are obligate host-associated organisms, lacking flagella and exhibiting varied morphology. The species from these genera also formed a strongly supported clade in phylogenetic trees based upon concatenated protein sequences; a monophyletic grouping of these genera and other genera displaying similar morphological characteristics was also observed in the 16S rRNA gene tree. A second clade (Clade II), supported by seven of the identified CSIs and phylogenetic trees based upon concatenated protein sequences, grouped together species from the genera Chromobacterium, Laribacter, and Pseudogulbenkiania that are rod-shaped bacteria, which display flagella-based motility and are capable of free living. The remainder of the CSIs were uniquely shared by smaller groups within these two main clades. Our analyses also provide novel insights into the evolutionary history of the Neisseriales and suggest that the CSIs that are specific for the Clade I species may play an important role in the evolution of obligate host-association within this order. On the basis of phylogenetic analysis, the identified CSIs, and conserved phenotypic characteristics of different Neisseriales genera, we propose a division of this order into two families: an emended family Neisseriaceae (corresponding to Clade I) containing the genera Alysiella, Bergeriella, Conchiformibius, Eikenella, Kingella, Neisseria, Simonsiella, Stenoxybacter, Uruburuella and Vitreoscilla and a new family, Chromobacteriaceae fam. nov., harboring the remainder of the genera from this order (viz. Andreprevotia, Aquaspirillum, Aquitalea, Chitinibacter, Chitinilyticum, Chitiniphilus, Chromobacterium, Deefgea, Formivibrio, Gulbenkiania, Iodobacter, Jeongeupia, Laribacter, Leeia, Microvirgula, Paludibacterium, Pseudogulbenkiania, Silvimonas, and Vogesella).

Chitinivorax tropicus gen. nov., sp. nov., a chitinolytic bacterium isolated from a freshwater lake

A facultatively anaerobic, chitinolytic bacterium, strain KL-9(T), was isolated from a freshwater lake in Taiwan and characterized by using a polyphasic taxonomic approach. Cells of strain KL-9(T) were gram-negative, rod-shaped, motile by means of a single polar flagellum and non-spore-forming. Growth occurred at 15-40 °C (optimum, 30-37 °C), at pH 7.0-9.0 (optimum, pH 8.0) and with 0-1.0 % NaCl (optimum, 0 %). The predominant fatty acids were summed feature 3 (comprising C(16 : 1)ω7c and/or C(16 : 1)ω6c) and C(16 : 0). The major isoprenoid quinone was Q-8. The DNA G+C content of strain KL-9(T) was 64.6 mol%. The polar lipid profile consisted of a mixture of phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol, phosphatidyldimethylethanolamine and several uncharacterized phospholipids and aminolipids. Phylogenetic analyses based on 16S rRNA gene sequences showed that strain KL-9(T) formed a distinct lineage with respect to closely related genera within the class Betaproteobacteria, being most closely related to members of the genera Leeia, Chitinimonas, Silvimonas and Andreprevotia. Levels of 16S rRNA gene sequence similarity with respect to the type strains of type species of these genera were below 91 %. On the basis of genotypic and phenotypic data, strain KL-9(T) is thus considered to represent a novel species of a new genus within the class Betaproteobacteria, for which the name Chitinivorax tropicus gen. nov., sp. nov. is proposed. The type strain of Chitinivorax tropicus is KL-9(T) ( = BCRC 80168(T) = LMG 25530(T)).