Altererythrobacter oceanensis sp. nov., isolated from the Western Pacific

Qipengyuania benthica sp. nov. and Qipengyuania profundimaris sp. nov., two novel Erythrobacteraceae members isolated from deep-sea environments

Two Gram-stain-negative, rod-shaped and non-motile strains, designated as DY56-A-20T and G39T, were isolated from deep-sea sediment of the Pacific Ocean and deep-sea seawater of the Indian Ocean, respectively. Strain DY56-A-20T was found to grow at 15-37 °C (optimum, 28 °C), at pH 6.0-10.0 (optimum, pH 6.5-7.0) and in 0.5-6.0 % (w/v) NaCl (optimum, 1.0-2.0 %), while strain G39T was found to grow at 10-42 °C (optimum, 35-40 °C), at pH 5.5-10.0 (optimum, pH 6.5-7.0) and in 0-12.0 % (w/v) NaCl (optimum, 1.0-2.0 %). The 16S rRNA gene sequence identity analysis indicated that strain DY56-A-20T had the highest sequence identity with Qipengyuania marisflavi KEM-5T (97.6 %), while strain G39T displayed the highest sequence identity with Qipengyuania citrea H150T (98.8 %). The phylogenomic reconstruction indicated that both strains formed independent clades within the genus Qipengyuania. The digital DNA-DNA hybridization and average nucleotide identity values between strains DY56-A-20T/G39T and Qipengyuania/Erythrobacter type strains were 17.8-23.8 % and 70.7-81.1 %, respectively, which are below species delineation thresholds. The genome DNA G+C contents were 65.0 and 63.5 mol% for strains DY56-A-20T and G39T, respectively. The predominant cellular fatty acids (>10 %) of strain DY56-A-20T were C17 : 1  ω6c, summed feature 8 and summed feature 3, and the major cellular fatty acids of strain G39T were C17 : 1  ω6c and summed feature 8. The major polar lipids in both strains were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine, sphingoglycolipid and an unidentified polar lipid. The only respiratory quinone present in both strains was ubiquinone-10. Based on those genotypic and phenotypic results, the two strains represent two novel species belonging to the genus Qipengyuania, for which the names Qipengyuania benthica sp. nov. and Qipengyuania profundimaris sp. nov. are proposed. The type strain of Q. benthica is DY56-A-20T (=MCCC M27941T=KCTC 92309T), and the type strain of Q. profundimaris is G39T (=MCCC M30353T=KCTC 8208T).

Microbial communities in carbonate precipitates from drip waters in Nerja Cave, Spain

Research on cave microorganisms has mainly focused on the microbial communities thriving on speleothems, rocks and sediments; however, drip water bacteria and calcite precipitation has received less attention. In this study, microbial communities of carbonate precipitates from drip waters in Nerja, a show cave close to the sea in southeastern Spain, were investigated. We observed a pronounced difference in the bacterial composition of the precipitates, depending on the galleries and halls. The most abundant phylum in the precipitates of the halls close to the cave entrance was Proteobacteria, due to the low depth of this sector, the direct influence of a garden on the top soil and the infiltration of waters into the cave, as well as the abundance of members of the order Hyphomicrobiales, dispersing from plant roots, and other Betaproteobacteria and Gammaproteobacteria, common soil inhabitants. The influence of marine aerosols explained the presence of Marinobacter, Idiomarina, Thalassobaculum, Altererythrobacter and other bacteria due to the short distance from the cave to the sea. Nineteen out of forty six genera identified in the cave have been reported to precipitate carbonate and likely have a role in mineral deposition.

Comparative Genomics Reveals Genetic Diversity and Metabolic Potentials of the Genus Qipengyuania and Suggests Fifteen Novel Species

Members of the genus Qipengyuania are heterotrophic bacteria frequently isolated from marine environments with great application potential in areas such as carotenoid production. However, the genomic diversity, metabolic function, and adaption of this genus remain largely unclear. Here, 16 isolates related to the genus Qipengyuania were recovered from coastal samples and their genomes were sequenced. The phylogenetic inference of these isolates and reference type strains of this genus indicated that the 16S rRNA gene was insufficient to distinguish them at the species level; instead, the phylogenomic reconstruction could provide the reliable phylogenetic relationships and confirm 15 new well-supported branches, representing 15 putative novel genospecies corroborated by the digital DNA-DNA hybridization and average nucleotide identity analyses. Comparative genomics revealed that the genus Qipengyuania had an open pangenome and possessed multiple conserved genes and pathways related to metabolic functions and environmental adaptation, despite the presence of divergent genomic features and specific metabolic potential. Genetic analysis and pigment detection showed that the members of this genus were identified as carotenoid producers, while some proved to be potentially aerobic anoxygenic photoheterotrophs. Collectively, the first insight into the genetic diversity and metabolic potentials of the genus Qipengyuania will contribute to better understanding of the speciation and adaptive evolution in natural environments.

IMPORTANCE The deciphering of the phylogenetic diversity and metabolic features of the abundant bacterial taxa is critical for exploring their ecological importance and application potential. Qipengyuania is a genus of frequently isolated heterotrophic microorganisms with great industrial application potential. Numerous strains related to the genus Qipengyuania have been isolated from diverse environments, but their genomic diversity and metabolic functions remain unclear. Our study revealed a high degree of genetic diversity, metabolic versatility, and environmental adaptation of the genus Qipengyuania using comparative genomics. Fifteen novel species of this genus have been established using a polyphasic taxonomic approach, expanding the number of described species to almost double. This study provided an overall view of the genus Qipengyuania at the genomic level and will enable us to better uncover its ecological roles and evolutionary history.

Qipengyuania soli sp. nov., Isolated from Mangrove Soil

A novel Gram-stain-negative, non-motile, and rod-shaped bacterial strain, designated as 6D36^T, was isolated from mangrove soil and characterized by using a polyphasic taxonomic approach. Strain 6D36^T was found to grow at 10-37 °C (optimum, 28 °C), at pH 6.0-9.0 (optimum, 7.0) and in 0-8% (w/v) NaCl (optimum, 3%). The predominant cellular fatty acids of strain 6D36^T were summed feature 8 (C_19:1 ω7c and/or C_18:1 ω6c) and C_17:1 ω6c; the major polar lipids were diphosphatidylglycerol, phosphatidylcholine, phosphatidylethanolamine, phosphatidylglycerol, and sphingoglycolipid; the sole respiratory quinone was Q-10. The phylogenetic analysis based on 16S rRNA gene sequences showed that strain 6D36^T fell into the genus Qipengyuania and was closely related to "Erythrobacter mangrovi" MCCC 1K03690^T (98.5%), Qipengyuania citrea CGMCC 1.8703^T (97.6%), and Qipengyuania pelagi JCM 17468^T (97.4%). The phylogenomic analysis indicated that strain 6D36^T formed an independent branch distinct from reference-type strains of species within this genus. The digital DNA-DNA hybridization and average nucleotide identity values between strain 6D36^T and the three type strains above were, respectively, 20.2-21.3% and 79.5-81.5%, of which were far below their respective threshold for species definition, implying that the strain represents a novel genospecies. The genomic DNA G + C content was 63.3%. Based on phenotypic and genotypic characteristics, strain 6D36^T is concluded to represent a novel species of the genus Qipengyuania, for which the name Qipengyuania soli sp. nov., is proposed. The type strain of the species is 6D36^T (= GDMCC 1.1977^T = KCTC 82333^T).

Genomic-based taxonomic classification of the family Erythrobacteraceae

The family Erythrobacteraceae, belonging to the order Sphingomonadales, class Alphaproteobacteria, is globally distributed in various environments. Currently, this family consist of seven genera: Altererythrobacter, Croceibacterium, Croceicoccus, Erythrobacter, Erythromicrobium, Porphyrobacter and Qipengyuania. As more species are identified, the taxonomic status of the family Erythrobacteraceae should be revised at the genomic level because of its polyphyletic nature evident from 16S rRNA gene sequence analysis. Phylogenomic reconstruction based on 288 single-copy orthologous clusters led to the identification of three separate clades. Pairwise comparisons of average nucleotide identity, average amino acid identity (AAI), percentage of conserved protein and evolutionary distance indicated that AAI and evolutionary distance had the highest correlation. Thresholds for genera boundaries were proposed as 70 % and 0.4 for AAI and evolutionary distance, respectively. Based on the phylo-genomic and genomic similarity analysis, the three clades were classified into 16 genera, including 11 novel ones, for which the names Alteraurantiacibacter, Altericroceibacterium, Alteriqipengyuania, Alteripontixanthobacter, Aurantiacibacter, Paraurantiacibacter, Parerythrobacter, Parapontixanthobacter, Pelagerythrobacter, Tsuneonella and Pontixanthobacter are proposed. We reclassified all species of Erythromicrobium and Porphyrobacter as species of Erythrobacter. This study is the first genomic-based study of the family Erythrobacteraceae, and will contribute to further insights into the evolution of this family.

Altererythrobacter maritimus sp. nov., isolated from seawater

A rod-shaped, Gram-staining-negative and orange-pigmented bacterium, designated strain HME9302^T, was isolated from seawater of the Yellow Sea in the Republic of Korea. The phylogenetic tree based on 16S rRNA gene sequences showed that strain HME9302^T formed a lineage within the genus Altererythrobacter, and was most closely related to Altererythrobacter aurantiacus O30^T with 96.7 % sequence similarity. The major fatty acids were summed feature 8 (comprising C18 : 1ω7c and/or C18 : 1ω6c), summed feature 3 (comprising C16 : 1ω7c and/or C16 : 1ω6c) and C16 : 0. The major respiratory quinone was ubiquinone-10. The major polar lipids were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine, sphingoglycolipid and four unidentified lipids. The DNA G+C content was 60.8 mol%. On the basis of the evidence presented in this study, strain HME9302^T represents a novel species of the genus Altererythrobacter, for which the name Altererythrobacter maritimus sp. nov. is proposed with the type strain HME9302^T (=KCTC 32463^T=KACC 17617^T=CECT 8417^T).

Altererythrobacter soli sp. nov., isolated from desert sand

An alkaliphilic strain designed MN-1T was isolated from a desert sand sample collected from Tengger desert, north-western China. To delineate its taxonomic position, this Gram-stain-negative, rod-shaped, strictly aerobic bacterium was subjected to a polyphasic taxonomic study. Growth was observed at temperatures from 4 to 37 °C (optimum 30-32 °C), at salinities from 0 to 2 % (optimum 1 %) and at pH from 6.5 to 12.0 (optimum 7.0-9.0). Phylogenetic analysis based on 16S rRNA gene sequencing showed that strain MN-1T was a member of the genus Altererythrobacterbut could be distinguished from recognized species of this genus. Compared to the reference strains, the novel strain was flagellated and motile by means of polar flagella. The predominant respiratory quinone was ubiquinone-10 and the major polar lipids were diphosphatidylglycerol, phosphatidylethanolamine, sphingoglycolipid, phosphatidylglycerol, phosphatidylcholine, one unidentified glycolipid, one unidentified phospholipid and four unidentified lipids. The predominant fatty acids were C18 : 1ω7c, summed feature 3 (C16 : 1ω7c and/or C16 : 1ω6c) and C16 : 0. These chemotaxonomic traits were in agreement with the characteristics of the genus Altererythrobacter. Strain MN-1T was most closely related to Altererythrobacter xinjiangensis S3-63T (96.9 % 16S rRNA gene sequence similarity), followed by Altererythrobacter dongtanensis JM27T (96.4 %) and Altererythrobacter marinus H32T (96.1 %). The G+C content of the genomic DNA of strain MN-1T was 67.0 mol%. On the basis of data from this polyphasic taxonomic study, strain MN-1T is proposed as the type strain of a novel species of the genus Altererythrobacter, named as Altererythrobacter soli sp. nov. (=KCTC 52135T=MCCC 1K02066T).

Description of Altererythrobacter aerius sp. nov., isolated from air, and emended description of the genus Altererythrobacter

A Gram-stain-negative, yellow-pigmented, ovoid to rod-shaped, strictly aerobic bacterial strain, designated 100921-2T, was isolated from air at the foot of Xiangshan Mountain. Phylogenetic and phenotypic analysis of the organism revealed that the isolate belongs to the genus Altererythrobacter. Strain 100921-2T showed high 16S rRNA gene sequence similarity (96.01-94.70 %) to other type strains of the genus Altererythrobacter, with the highest similarity to Altererythrobactermarensis MSW-14T. Growth of strain 100921-2T was observed at 4-50 °C (optimum, 30 °C), at pH 4.5-10.0 (optimum, pH 7.0) and at salinities of 0-10 % (w/v) NaCl (optimum 0-0.5 %). The major fatty acids were C18 : 1ω7c (27.8 %), C17 : 1ω6c (23.1 %), 11-methyl C18 : 1ω7c(11.9 %), summed feature 3 (9.1 %) and C15 : 0 2-OH (7.9 %). The predominant respiratory quinone was ubiquinone-10 (Q-10). Polar lipid analysis indicated the presence of diphosphatidylglycerol, sphingoglycolipid, phosphatidylethanolamine, phosphatidylglycerol, phosphatidylcholine, two unknown phospholipids, five unknown polar lipids and two unknown glycolipids. The DNA G+C content of the type strain was 67.5 mol%. On the basis of the data from the polyphasic characterization, strain 100921-2T represents a novel species, for which the name Altererythrobacter aerius sp. nov. is proposed. The type strain is 100921-2T (=CFCC 14287T=KCTC 42844T).