Sphingomonas morindae sp. nov., isolated from Noni (Morinda citrifolia L.) branch

Genomic-based taxonomic classification of the order Sphingomonadales

The order Sphingomonadales strains are globally distributed in various biomes and are renowned for their biodegradable and biosynthesis capabilities. At present, it consists of 4 families and 49 genera making it the third largest order within the class Alphaproteobacteria. However, their taxonomy remains complex, especially due to polyphyly in the family Sphingomonadaceae. In this study, we collected 429 Sphingomonadales type strain genomes, reconstructed robust phylogenomic relationships, and proposed delineation thresholds at the genus and family levels based on average amino acid identities (AAI) and evolutionary distances (ED). Based on the maximum-likelihood and Bayesian phylogenomic trees reconstructed by two molecular sets determined by orthologous sequence identity and the Genome Taxonomy Database, the consensus degree values were all higher than 90%, revealing that those phylogenomic trees had similar topological structures. By confirming monophyletic taxa and determining stable nodes, we reclassified the order Sphingomonadales into thirteen families including nine novel ones. AAI calculations indicated that the average intra-family AAI values ranged from 0.62 to 0.84, while inter-family ones were 0.51 to 0.60. ED summaries demonstrated that the average and median intra-family ED values were 0.16 to 0.57, and inter-family ones ranged from 0.50 to 1.22. Comparisons of AAI and ED values calculated by using genomic and phylogenetic analyses supported that those 13 families were significantly separated with p values < 2.2×10-16. Thus, it was speculated that the AAI and ED thresholds for distinguishing different families were <0.6 and >0.5, respectively. Additionally, we reclassified 163 species into new genera with their phylogenetic topologies, according to the previous genus AAI and ED boundaries of 0.7 and 0.4. Our study is the first genomic-based study of the order Sphingomonadales and will promote further insights into the evolution of this order.

Metabolomic Analysis of Carotenoids Biosynthesis by Sphingopyxis sp. USTB-05

Carotenoids belonging to the class of tetraterpenoids have extensive applications in medicine, food, nutrition, cosmetics, and feed. Among them, lutein and zeaxanthin can prevent macular degeneration in the elderly, which is very important for protecting vision. Here, we introduce the first metabolomic analysis of Sphingopyxis sp. USTB-05, aiming to shed light on the biosynthesis of carotenoids. Sphingopyxis sp. USTB-05 has the complete methylerythritol 4-phosphate (MEP) pathway and carotenoid biosynthesis pathway, especially involved in the bioconversion of zeaxanthin, violaxanthin, and astaxanthin. Metabolomic profiling identified seven carotenes and six xanthophylls synthesized by Sphingopyxis sp. USTB-05. Zeaxanthin, in particular, was found to be the most abundant, with a content of 37.1 µg/g dry cells. Collectively, the results presented herein greatly enhance our understanding of Sphingopyxis sp. USTB-05 in carotenoids biosynthesis, and thus further accelerate its fundamental molecular investigations and biotechnological applications.

Comparative Genomic Analysis of Sphingomonas morindae sp. NBD5 and Sphingopyxis sp. USTB-05 for Producing Macular Pigment

Sphingomonas morindae sp. NBD5, which we previously identified and tested, is a new bacterial strain for producing lutein. Here, based on the next-generation sequencing technology, we analyzed high throughput genomic sequences and compared related functional genes of Sphingomonas morindae sp. NBD5 and Sphingopyxis sp. USTB-05. The genome of Sphingomonas morindae sp. NBD5 has two sets of chromosomes, which is 4,239,716 bp and harbors 3882 protein coding genes. There are 59 protein-coding genes related to the macular pigment (MP) biosynthesis, of which four genes (ackA, pgm, gpmI and pckA) are unique. These genes, pckG, porB, meh, and fldA, are unique in Sphingopyxis sp. USTB-05. The analysis of Sphingomonas morindae sp. NBD5 and Sphingopyxis sp. USTB-05 genomes gives an insight into the new pathway for MP production. These genes for the transformation of glucose to MP were also found in Sphingomonas morindae sp. NBD5 and Sphingopyxis sp. USTB-05. This study expands the understanding of the pathway for complete biosynthesis of MP by Sphingomonas morindae sp. NBD5 and Sphingopyxis sp. USTB-05.

High-throughput sequencing-based analysis of the composition and diversity of endophytic bacterial community in seeds of upland rice

Upland rice is an ecotype crop resulting from the long-term domestication and evolution of rice in dry land without a water layer. Generally, the stems and leaves are thick and luxuriant, while the leaves also typically broad and light. The root system is developed with abundant root hair, and the osmotic pressure of the root and cell juice concentration in the leaves is high, while this plant is drought-resistant, heat-resistant, and water absorbent. This study aims to reveal the "core flora" of the endophytes in upland rice seeds by examining their diversity and community structures. It further intends to reveal the impact of the soil environment on the formation of endophyte community structures in upland rice seeds by comparing the environmental soil microorganisms in upland rice habitats. In this study, high-throughput sequencing technology based on the Illumina Hiseq 2500 platform was used to investigate the structure and diversity of endophytic bacterial communities using upland rice varieties collected from different locations and soil samples from unified planting sites as materials. Here, 42 endophytic OTUs were found to coexist in the 14 samples. At the phylum level, the first dominant phyla in all the samples were Proteobacteria (93.81-99.99%). At the genus level, Pantoea (8.77-87.77%), Pseudomonas (1.15-61.58%), Methylobacterium (0.40-4.64%), Sphingomonas (0.26-3.85%), Microbacterium (0.01-4.67%) and Aurantimonas (0.04-4.34%), which represent the core microflora in upland rice seeds, served as the dominant genera that coexisted in all the upland rice seeds tested. This study significant for the isolation, screening, functional evaluation, and re-action of various functional microorganisms in upland rice to improve its agronomic traits. It also provides a specific reference for the interaction between microorganisms and plants.

Sphingomonas chungangi sp. nov., a bacterium isolated from garden soil sample

A novel bacterial strain, designated MAH-6^T, was isolated from a garden soil sample. Cells were Gram-stain-negative, aerobic, non-motile and rod-shaped. The colonies were light yellow, smooth, circular and 0.6-1.2 mm in diameter when grown on nutrient agar for 3 days. Strain MAH-6^T grew at 15-35 °C, at pH 5.0-7.0 and with 0-0.5 % NaCl. Cell growth occurred on nutrient agar and Reasoner's 2A (R2A) agar. The strain was positive for both catalase and oxidase tests. Cells were able to hydrolyse starch, aesculin, Tween 20 and Tween 80. According to 16S rRNA gene sequence comparisons, the isolate was identified as a member of the genus Sphingomonas and was most closely related to Sphingomonas polyaromaticivorans B2-7^T (98.2 % sequence similarity), Sphingomonas oligoaromativorans SY-6^T (96.9 %) and Sphingomonas morindae NBD5^T (96.6 %). The novel strain MAH-6^T has a draft genome size of 4 370 740 bp (28 contigs), annotated with 4199 protein-coding genes, 46 tRNA and three rRNA genes. The genomic DNA G+C content of the strain was determined to be 66.2 mol% and the predominant isoprenoid quinone is Q-10. The major fatty acids were identified as summed feature 8 (comprising C_18 : 1  ω7c and/or C_18 : 1  ω6c), C_14 : 0 2OH and C_16 : 0. The main polar lipids were phosphatidylcholine, sphingoglycolipid, phosphatidylethanolamine, phosphatidylglycerol and diphosphatidylglycerol. Based on the results of phenotypic, genotypic, chemotaxonomic and DNA-DNA hybridization studies, strain MAH-6^T represents a novel species, for which the name Sphingomonas chungangi sp. nov. is proposed, with MAH-6^T as the type strain (=KACC 19292^T=CGMCC1.13654^T).

Bacillus fungorum sp. nov., a bacterium isolated from spent mushroom substrate

A facultatively anaerobic, Gram-stain-positive, spore-forming Bacillus strain, 17-SMS-01^T, isolated from spent mushroom substrate in the Fangshan District, Beijing, PR China, was initially identified as a Bacillus cereus group species based on 16S rRNA gene sequences. Strain 17-SMS-01^T had the highest sequence similarities to Bacillus wiedmannii FSL W8-0169^T (99.9 %), Bacillus albus N35-10-2^T (99.9 %), Bacillus luti TD41^T (99.9 %) and Bacillus proteolyticus TD42^T (99.9 %). However, the average nucleotide identity (ANI) and digital DNA-DNA hybridization (DDH) values between strain 17-SMS-01^T and the most closely related species were less than the previously proposed cut-off values of 96 % (ANI) and 70 % (DDH) for differentiating species within the genus, suggesting that this strain represents a novel Bacillus group species. The fatty acid profile of strain 17-SMS-01^T, which showed a predominance of iso-C_15 : 0 and anteiso-C_15 : 0, supported the allocation of the strain to the genus Bacillus. The predominant menaquinone was MK-7 (100%). The major polar lipids were diphosphatidylglycerol, phosphatidyl ethanolamine, phosphatidyl glycerol, an unidentified aminophospholiped and unidentified lipids. The DNA G+C content of the novel strain was 35.0 mol%. The results of physiological and biochemical tests also allowed the phenotypic differentiation of strain 17-SMS-01^T from the most closely related recognized species. On the basis of the phylogenetic and phenotypic evidence, strain 17-SMS-01^T represents a novel Bacillus species, for which the name Bacillus fungorum sp. nov. is proposed. Type strain of the novel species is 17-SMS-01^T (=MCCC 1K03483^T=KCTC 33949^T).

Sphingomonas difficilis sp. nov., a difficultly cultivable bacterium that grows on solid but not in liquid medium, isolated from an abandoned lead-zinc mine

A difficult to cultivate bacterial strain, designated 1PNM-26^T, isolated from a lead-zinc mine, was investigated using a polyphasic taxonomic approach. The strain was able to grow on solid medium but not in liquid medium. Cells were Gram-reaction-negative, aerobic, non-spore-forming, non-motile and rod-shaped. It showed positive reactions for catalase and oxidase and hydrolysis of aesculin. The results of phylogenetic analyses based on 16S rRNA gene sequences indicated that strain 1PNM-26^T represents a member of the genus Sphingomonas and forms a stable cluster with Sphingomonas morindae KCTC 42183^T, Sphingomonas polyaromaticivorans JCM 16711^T and Sphingomonas oligoaromativorans NBRC 105508^T. The major fatty acids were summed feature 8 (C18 : 1ω7c and/or C18 : 1ω6c), summed feature 3 (C16 : 1ω7c and/or C16 : 1ω6c) and C16 : 0. C14 : 0 2-OH was present as the major hydroxyl fatty acid. The major polyamine was sym-homospermidine, and ubiquinone 10 (Q-10) was the predominant respiratory quinone. The genomic DNA G+C content of strain 1PNM-26^T was determined to be 66.3±0.3 mol%, and the polar lipids consisted of sphingoglycolipid, phosphatidylglycerol, diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine, phosphatidyldimethylethanolamine, phosphatidylmonomethylethanolamine, an unidentified glycolipid, three unidentified aminolipids and three unidentified lipids. The phenotypic, phylogenetic and chemotaxonomic results strongly supported the hypothesis that strain 1PNM-26^T represents a novel species of the genus Sphingomonas, for which the name Sphingomonasdifficilis sp. nov. is proposed. The type strain is 1PNM-26^T (=GDMCC 1.664^T=KCTC 42758^T=DSM 27573^T).

Bacillus ciccensis sp. nov., isolated from maize (Zea mays L.) seeds

Two Gram-stain-positive bacterial strains, designated as 5L6^T and 6L6, isolated from seeds of hybrid maize (Zea mays L., Jingke 968) were investigated using a polyphasic taxonomic approach. The cells were aerobic, motile, endospore-forming and rod-shaped. Phylogenetic analysis based on 16S rRNA gene sequences showed that the isolates were recognized as a species of the genus Bacillus, to which the five closest neighbours are Bacillus solani FJAT-18043^T (99.8 % similarity), Bacillus horneckiae DSM 23495^T (97.7 %), Bacillus eiseniae A1-2^T (97.4 %), Bacillus kochii WCC 4582^T (97.1 %) and Bacillus purgationiresistens DS22^T (97.0 %). The DNA G+C content of strain 5L6^T was 37.4 mol%. Its polar lipid profile consisted of diphosphatidylglycerol, phosphatidylglycerol and phosphatidylethanolamine. The predominant respiratory quinone was MK-7 and the major fatty acids were iso-C15 : 0, anteiso-C15 : 0, iso-C16 : 0, iso-C14 : 0, anteiso-C17 : 0 and C16 : 1 ω7c alcohol. The cell-wall peptidoglycan contained ornithine, serine, aspartic acid, glutamic acid and alanine while diaminopimelic acid could not be detected. Strains 5L6^T and 6L6 were clearly distinguished from the type strains of related validly named species using phylogenetic analysis, DNA-DNA hybridization, fatty acid analysis, peptidoglycan analysis and comparison of a range of physiological and biochemical characteristics. The genotypic and phenotypic data show that strains 5L6^T and 6L6 represent a novel species of the genus Bacillus, for which the name Bacillusciccensis sp. nov. is proposed. The type strain is 5L6^T (=KCTC 33663^T=CICC 23855^T=DSM 104513^T).

Sphingomonaszeicaulis sp. nov., an endophytic bacterium isolated from maize root

A novel Gram-staining-negative, aerobic and rod-shaped strain designated 541T was isolated from surface-sterilized root tissue of maize, collected from the Fangshan District of Beijing, People's Republic of China, and was subjected to a taxonomic study using a polyphasic approach. According to a phylogenetic tree based on 16S rRNA gene sequences, strain 541T represented a member of the genus Sphingomonas and clustered with Sphingomonas sanxanigenens DSM 19645T, with which it shared the highest 16S rRNA gene sequence similarity (98.8 %). The predominant respiratory quinone was ubiquinone-10 (Q-10), the major polyamine was sym-homospermidine and the major cellular fatty acids were C18 : 1ω7c (50.9 %), C16 : 0 (22.0 %) and C14 : 0 2-OH (11.4 %). The major polar lipids were phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol, phosphatidylcholine and sphingoglycolipid. The DNA G+C content was 64.7 mol%. DNA-DNA relatedness between strain 541T and its closest phylogenetic relative Sphingomonas sanxanigenens DSM 19645T was 50.8 %. The results of physiological and biochemical tests and the differences in the fatty acid profiles allowed a clear phenotypic differentiation of strain 541T from closely related species of the genus Sphingomonas. Strain 541T represents a novel species within the genus Sphingomonas, for which the nameSphingomonas zeicaulis sp. nov. is proposed, with the type strain 541T (=CGMCC 1.15008T=DSM 100587T).