Taxonomic revision of the family Aurantimonadaceae: proposal of Dennerimonas gen. nov., Mesocryomonas gen. nov., Rathsackimonas gen. nov. and Plantimonas gen. nov., along with the reclassification of Jeongeupella Jiang et al. 2024 as a later heterotypic synonym of Antarcticirhabdus Du et al. 2023

Phylogenetic analysis of the genus Aureimonas, utilizing both 16S rRNA gene sequences and comprehensive whole-genome data, revealed its polyphyletic nature, necessitating a revision to accommodate phylogenetically distinct species. Based on established threshold values for genus demarcation - specifically, 16S rRNA gene similarity, Average Amino Acid Identity and Percentage of Conserved Proteins - a notably substantial divergence was observed within the genus Aureimonas, and the division of Aureimonas into four distinct genera is strongly supported. To address this, we propose the establishment of four new genera: Dennerimonas gen. nov., Mesocryomonas gen. nov., Rathsackimonas gen. nov. and Plantimonas gen. nov. These classifications accommodate species that are significantly divergent from the type species of Aureimonas, thereby more accurately reflecting their distinct evolutionary lineages. Additionally, Aureimonas glaciistagni is proposed to be reclassified within the genus Jiella as Jiella glaciistagni comb. nov. based on phylogenetic evidence indicating a closer evolutionary relationship to Jiella species than to other members of Aureimonas. Our analysis, which included assessments of 16S rRNA gene similarity, Average Nucleotide Identity, and digital DNA-DNA hybridization values exceeding species delineation thresholds, further supports the reclassification of Jeongeupella Jiang et al. 2024 as a later heterotypic synonym of Antarcticirhabdus Du et al. 2023.

Description of Aliirhizobium terrae sp. nov., A Plant Growth-Promoting Bacterium Isolated from a Maize-Rice Rotation Agriculture Field

A polyphasic taxonomic approach was used to characterize a novel bacterium, designated strain CC-CFT758T, isolated from a maize-rice rotation agriculture field in Taiwan. The cells are aerobic, Gram-stain-negative, rod-shaped, positive for catalase and oxidase, and grow at 20-30 °C (optimal 30 ℃), at pH 6.0-8.0 (optimal 8.0), and with 0-4% (w/v) NaCl (optimum, 2-3%). Phylogenetic analysis based on 16S rRNA gene sequencing, the strain CC-CFT758T belongs to the genus "Aliirhizobium" of the family Rhizobiaceae. The closest known relatives of this strain are "Aliirhizobium wenxiniae" 166T (with 98.7% similarity), "Aliirhizobium cellulosilyticum" SEMIA 448T (with 97.9% similarity), and "Aliirhizobium smilacinae" PTYR-5T (with 97.0% similarity). The genome size was 5.9 Mbp, with a G + C content of 60.6%. Values of digital DNA-DNA hybridization between the strain and closely related species were 29.5% for "Ali. cellulosilyticum", and 23.9% for "Ali. wenxiniae" and "Ali. smilacinae". Strain CC-CFT758T exhibited the highest orthologous average nucleotide identity (OrthoANI) values with members of the genus "Aliirhizobium", ranging from 80.4 to 81.6% (n = 3). Chemotaxonomical analysis indicated that strain CC-CFT758T contained C16:0, C16:0 3OH, C19:0 cyclo ω8c, C14:0 3OH/iso-C16:1 I, and C18:2 ω6,9c/ante C18:0 as dominant fatty acids, and the major polyamines were putrescine and spermidine. The polar lipids comprised diphosphatidylglycerol, phosphatidylcholin, phosphatidylglycerol, phosphatidylethanolamine, phosphatidylmonomethylethanolamine, seven unidentified aminolipids, three unidentified phospholipids, and two unidentified polar lipids. Strain CC-CFT758T exhibited distinct phylogenetic, phenotypic, and chemotaxonomic characteristics, as well as unique results in comparative analysis of 16S rRNA gene sequence, OrthoANI, AAI, dDDH, and phylogenomic placement. Therefore, this strain represents a new species of the genus "Aliirhizobium", for which the name Aliirhizobium terrae sp. nov. is proposed, with the type strain is CC-CFT758T (= BCRC 81364T = JCM 35482T).

Jeongeuplla avenae gen. nov., sp. nov., a novel β-carotene-producing bacterium that alleviates salinity stress in Arabidopsis

A novel endophytic bacterium, designated DY-R2A-6T, was isolated from oat (Avena sativa L.) seeds and found to produces β-carotene. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain DY-R2A-6T had 96.3% similarity with Jiella aquimaris LZB041T, 96.0% similarity with Aurantimonas aggregate R14M6T and Aureimonas frigidaquae JCM 14755T, and less than 95.8% similarity with other genera in the family Aurantimonadaceae. The complete genome of strain DY-R2A-6T comprised 5,929,370 base pairs, consisting of one full chromosome (5,909,198 bp) and one plasmid (20,172 bp), with a G + C content was 69.1%. The overall genome-related index (OGRI), including digital DNA-DNA hybridization (<20.5%), ANI (<79.2%), and AAI (<64.2%) values, all fell below the thresholds set for novel genera. The major cellular fatty acids (>10%) of strain DY-R2A-6T were C16:0, C19:0 cyclo ω8c, and summed feature 8 (C18:1ω7c and/or C18:1ω6c). Ubiquinone-10 was the main respiratory quinone. We identified the gene cluster responsible for carotenoid biosynthesis in the genome and found that the pink-pigment produced by strain DY-R2A-6T is β-carotene. In experiment with Arabidopsis seedlings, co-cultivation with strain DY-R2A-6T led to a 1.4-fold increase in plant biomass and chlorophyll content under salt stress conditions, demonstrating its capacity to enhance salt stress tolerance in plants. Moreover, external application of β-carotene to Arabidopsis seedlings under salt stress conditions also mitigated the stress significantly. Based on these findings, strain DY-R2A-6T is proposed to represent a novel genus and species in the family Aurantimonadaceae, named Jeongeuplla avenae gen. nov., sp. nov. The type strain is DY-R2A-6T (= KCTC 82985T = GDMCC 1.3014T). This study not only identified a new taxon but also utilized genome analysis to predict and confirm the production of β-carotene by strain DY-R2A-6T. It also demonstrated the ability of this strain to enhance salt stress tolerance in plants, suggesting potential application in agriculture to mitigate environmental stress in crops.

Complete Genome and Plasmid Sequences of the Psychrotolerant Aureimonas Strain SA4125, Isolated from Antarctic Moss Vegetation

The complete genome sequences of Aureimonas sp. strain SA4125 and its native plasmid pSA4125 were determined. The genome sequence comprises 4,968,066 bp, with a GC content of 66.0%, and contains 4,691 coding DNA sequences (CDSs), 3 rRNA operons, and 50 tRNAs. The native plasmid comprises 131,777 bp, with a GC content of 62.3%, and contains 138 CDSs.

Aureimonas mangrovi sp. nov., a marine alphaproteobacterium isolated from mangrove sediment in Thailand

Two bacterial strains, designated as 1-4-3^T and 1-4-4, were isolated from a mangrove sediment cultured with coastal seawater. The cells were Gram-stain-negative, motile, short, rod-shaped bacteria with flagella. Growth occurred at 4-37 °C, pH 7.0-9.0, and 0-7% NaCl. The predominant fatty acids of the novel strains were C_18 : 1  ω7c, C_19 : 0 cyclo ω8c, C_18 : 0, and C_16 : 0. A phylogenetic analysis based on 16S rRNA gene sequences and whole genome phylogeny analysis based on distance matrix revealed an affiliation between the two strains and the genus Aureimonas, with closest sequence similarity to A. populi 4M3-2^T (96.41 and 96.64% similarity, respectively) and A. glaciistagni (96.01 and 96.23% similarity, respectively). The DNA G+C content of strain 1-4-3^T was 66.80 mol%. Strain 1-4-3^T displayed low DNA-DNA relatedness to A. populi 4M3-2^T, with an average nucleotide identity value of 77.47 % and digital DNA-DNA hybridization value of 22.83 %. Genotypic, chemotaxonomic, and phenotypic data indicate that strains 1-4-3^T and 1-4-4 represent a novel species of the genus Aureimonas, for which we propose the name Aureimonas mangrovi sp. nov. The type strain is 1-4-3^T (=LMG 31693^T=CGMCC 1.18507^T).

Aureimonas fodinaquatilis sp. nov., isolated from coal mine wastewater

A Gram stain-negative, aerobic, non-motile, short, rod-shaped bacterial strain CAU 1482^T was isolated from coal mine wastewater in Hongcheon, Korea. It grew well at 30 °C, pH 8.5, 2% NaCl (w/v). 16S rRNA-based phylogeny indicated that CAU 1482^T forms a distinct lineage within Aureimonas with high similarity to Aureimonas frigidaquae CW5^T (98.2%), Aureimonas altamirensis S21B^T (98.0%), and Aureimonas glaciei B5-2^T (96.3%). The predominant cellular fatty acids were C_18:1 2-OH, C_16:0, C_18:1 ω7c, and/or C_18:1 ω6c (summed feature 8), with Q-10 as the major isoprenoid quinone. The polar lipid profile comprised diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine, two unidentified aminolipids, and three unidentified lipids. The 3.9-Mb genome included 8 contigs and 3599 protein-coding genes with a 56.7 mol% G + C content. Average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values between strain CAU 1482^T and closely related strains of A. frigidaquae CW5^T and A. altamirensis S21B^T were 72.2‒72.4% and 18.7‒18.8%, respectively. These phenotypic, chemotaxonomic, and phylogenetic data support CAU 1482^T as a novel Aureimonas species, for which the name Aureimonas fodinaquatilis sp. nov. is proposed. The type strain is CAU 1482^T (= KCTC 62995^T = NBRC 113692^T).

A Comparative Analysis of Ash Leaf-Colonizing Bacterial Communities Identifies Putative Antagonists of Hymenoscyphus fraxineus

In the last few years, the alarming spread of Hymenoscyphus fraxineus, the causal agent of ash dieback, has resulted in a substantial threat to native ash stands in central and northern Europe. Since leaves and leaf petioles are the primary infection sites, phyllosphere microorganisms are presumed to interact with the pathogen and are discussed as a source of biocontrol agents. We studied compound leaves from susceptible and visible infection-free trees in four ash stands with a high likelihood of infection to assess a possible variation in the bacterial microbiota, depending on the health status of the trees. The bacterial community was analyzed by culture-independent 16S rRNA gene amplicon sequencing and through the isolation and taxonomic classification of 2,589 isolates using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). The bacterial community structure did not show significant differences. However, a set of amplicon sequence variants (ASVs) and MALDI groups belonging to Luteimonas, Aureimonas, Pseudomonas, Bacillus, and Paenibacillus were distinctly increased in tolerant trees, which may be associated with the ability of the tree to resist the pathogen. The most obvious differences were observed for Luteimonas, a genus that is also exclusively present in the healthy core microbiome. In a first in vitro screen of antagonists, approximately 11% of total isolates suppressed the growth of H. fraxineus, but a statistical test with two different H. fraxineus strains confirmed only the antagonistic activity of 8% of these isolates. The antagonistic isolates were assigned to Bacillus velezensis, Pantoea vagans, and Pseudomonas caspiana. Overall, our study provides a set of isolates or phylogenetic groups that might be involved in the process that prevents the penetration and spread of H. fraxineus. In the next step, in planta experiments are required with a longer period of exposure to H. fraxineus to evaluate effective isolates or consortia of isolates acting through direct antagonism or competition or indirectly by inducing resistance.

Aureimonas leprariae sp. nov., Isolated from a Lepraria sp. Lichen

A Gram-negative, motile, aerobic and coccoid rod-shaped bacterium, designated strain YIM132180^T, was isolated from a Lepraria sp. lichen collected from Pu'er, Yunnan Province, China. The strain grew at 15-35 °C (optimum, 25-28 °C), at 0-2% (w/v) NaCl (optimum, 0-1%) and at pH 6.0-9.0 (optimum, pH 7.0). The 16S rRNA gene sequence showed that strain YIM132180^T had highest similarity (96.4%) with Aureimonas endophytica 2T4P-2-4^T, followed by Aureimonas ureilytica NBRC 106430^T (95.7%) and Aureimonas rubiginis CC-CFT034^T (95.6%). Phylogenetic analysis showed that the strain grouped with species of the genus Aureimonas. The genomic sequence was 4,779,519 bp and contained 4584 coding sequences (CDSs), 54 RNA genes, 3 complete rRNA genes and 47 tRNA genes. The major fatty acids (>10%) of strain YIM132180^T were C_18:1ω7c, C-_16:0 and C_19:0 cyclo ω8c. The predominant menaquinone was ubiquinone 10 (Q-10). The polar lipid profile comprised diphosphatidylglycerol, phosphatidylcholine, phosphatidylmethylethanolamine, phosphatidylethanolamine, phosphatidylglycerol, unidentified phospholipid, amino lipid, lipid and most importantly sulfoquinovosyldiacylglycerol (SQDG). Based on the draft genome sequence, the G +C content of strain YIM132180^T was 68.4 mol%. The results of the polyphasic taxonomic study, including phenotypic, chemotaxonomic, and phylogenetic analyses, showed that strain YIM132180^T represents a novel species of the genus Aureimonas, for which the name Aureimonas leprariae sp. nov. is proposed. The type strain is YIM 132180^T (=KCTC 72462^T = CGMCC 1.17389^T).

Mangrovicella endophytica gen. nov., sp. nov., a new member of the family Aurantimonadaceae isolated from Aegiceras corniculatum

A Gram-negative, aerobic, motile and short-rod-shaped bacterium, designated strain 5T4P-12-1^T, was isolated from a piece of surface-sterilized bark of Aegiceras corniculatum collected from Cotai Ecological Zones in Macao, China and tested by a polyphasic approach to clarify its taxonomic position. Strain 5T4P-12-1^T grew optimally with 0-1 % (w/v) NaCl at 30 °C and at pH 7.0-8.0. The 16S rRNA gene sequence of strain 5T4P-12-1^T had the highest similarity (96.7 %) to Aureimonas altamirensis DSM 21988^T. Phylogenic analysis based on 16S rRNA gene sequences and coding sequences of 98 protein clusters showed that the strain represented a novel genus of the family Aurantimonadaceae. The predominant quinone system of strain 5T4P-12-1^T was ubiquinone 10. The polar lipid profile contained diphosphatidylglycerol, phosphatidylglycerol, phosphatidylcholine, phosphatidylethanolamine, phosphatidylmethylethanolamine, an unidentified aminophospholipid, three unidentified aminolipids, three unidentified phospholipids and three unidentified lipids. The major fatty acids (>10 % of total fatty acids) were C18 : 1ω7c (55.4 %) and C18 : 1 2-OH (15.6 %). The DNA G+C content of strain 5T4P-12-1^T was 66.5 mol%. Based on the phylogenic, phenotypic and chemotaxonomic features, strain 5T4P-12-1^T is considered to represent a novel species of a new genus in the family Aurantimonadaceae, for which the name Mangrovicella endophytica gen. nov., sp. nov. is proposed. The type strain is 5T4P-12-1^T (=KCTC 62053^T=CGMCC 1.16279 ^T).

Aureimonas glaciistagni sp. nov., isolated from a melt pond on Arctic sea ice

A Gram-staining-negative, motile, aerobic and rod-shaped bacterial strain, PAMC 27157T, was isolated from a melt pond on sea ice in the Chukchi Sea. Phylogenetic analysis of the 16S rRNA gene sequence of strain PAMC 27157T revealed an affiliation to the genus Aureimonas with the closest sequence similarity (96.2 %) to that of Aureimonas phyllosphaerae. Strain PAMC 27157T grew optimally at 30 °C and pH 7.0 in the presence of 3.5 % (w/v) NaCl. The major polar lipids were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine, phosphatidylmonomethylethanolamine, sulfoquinovosyldiacylglycerol and an unidentified aminolipid. The major cellular fatty acid was summed feature 8 (C18 : 1ω7c and/or C18 : 1ω6c, 83.1 %) and the major respiratory quinone was Q-10. The genomic DNA G+C content was 69.1 mol%. The combined phylogenetic, phenotypic and chemotaxonomic data showed that strain PAMC 27157T could be clearly distinguished from species of the genus Aureimonas with validly published names. Thus, strain PAMC 27157T should be classified as representing a novel species in the genus Aureimonas, for which the name Aureimonas glaciistagni sp. nov. is proposed. The type strain is PAMC 27157T ( = KCCM 43049T = JCM 30183T).

Jiella aquimaris gen. nov., sp. nov., isolated from offshore surface seawater

A Gram-stain-negative, strictly aerobic and rod-shaped motile bacterium with peritrichous flagella, designated strain LZB041(T), was isolated from offshore surface seawater of the East China Sea. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain LZB041(T) formed a lineage within the family ' Aurantimonadaceae' that was distinct from the most closely related genera Aurantimonas (96.0-96.4% 16S rRNA gene sequence similarity) and Aureimonas (94.5-96.0%). Optimal growth occurred in the presence of 1-7% (w/v) NaCl, at pH 7.0-8.0 and at 28-37 °C. Ubiquinone-10 was the predominant respiratory quinone. The major fatty acids (>10% of total fatty acids) were C(18 : 1)ω7c and/or C(18 : 1)ω6c (summed feature 8) and cyclo-C(19 : 0)ω8c. The major polar lipids were phosphatidylglycerol, diphosphatidylglycerol, phosphatidylcholine, phosphatidylethanolamine, phosphatidylmonomethylethanolamine, one unknown aminolipid, one unknown phospholipid and one unknown polar lipid. The DNA G+C content of strain LZB041(T) was 71.3 mol%. On the basis of polyphasic analysis, strain LZB041(T) is considered to represent a novel species of a new genus in the class Alphaproteobacteria , for which the name Jiella aquimaris gen. nov., sp. nov. is proposed. The type strain of the type species is LZB041(T) ( = JCM 30119(T) = MCCC 1K00255(T)).

Youngimonas vesicularis gen. nov., sp. nov., of the family Rhodobacteraceae, isolated from surface seawater, reclassification of Donghicola xiamenensis Tan et al. 2009 as Pseudodonghicola xiamenensis gen. nov., comb. nov. and emended description of the genus Donghicola Yoon et al. 2007

A Gram-staining-negative, non-pigmented, strictly aerobic, rod-shaped, non-spore-forming, non-motile bacterium, devoid of bacteriochlorophyll, designated strain CC-AMW-ET, was isolated from surface seawater off the coast at Kending, Taiwan. Strain CC-AMW-ET shared 95.7 and 93.9 % 16S rRNA gene sequence similarity, respectively, with the type strains of the type species of the genera Donghicola ( Donghicola eburneus SW-277T) and Roseovarius ( Roseovarius tolerans EL-172T). The predominant (>75 % of the total) fatty acid was summed feature 8 (C18 : 1ω6c and/or C18 : 1ω7c). The polar lipid profile included major amounts of diphosphatidylglycerol, phosphatidylglycerol, phosphatidylcholine, phosphatidylethanolamine and an unidentified aminolipid. In addition, moderate amounts of an unidentified lipid and trace amounts of an unidentified phospholipid were detected. The DNA G+C content was 67.9 mol%. Ubiquinone Q-10 was the sole respiratory quinone. Based on its phylogenetic distinctiveness and distinguishing phenotypic characteristics (in particular its polar lipid pattern), we conclude that strain CC-AMW-ET represents a novel genus and species of the family Rhodobacteraceae , for which the name Youngimonas vesicularis gen. nov., sp. nov. is proposed. The type strain of Youngimonas vesicularis is CC-AMW-ET ( = JCM 18819T = BCRC 80549T). In addition, an emended description of the genus Donghicola Yoon et al. 2007 and the reclassification of Donghicola xiamenensis Tan et al. 2009 as Pseudodonghicola xiamenensis gen. nov., comb. nov. (type strain Y-2T = MCCC 1A00107T = LMG 24574T = CGMCC 1.7081T) are proposed.