Sphingobium rhizovicinum sp. nov., isolated from rhizosphere soil of Fortunella hindsii (Champ. ex Benth.) Swingle

Artemisia argyi leaf powder improves soil properties and recruits Sphingobium bacteria to promote the growth and yield of Pinellia ternata

Recent research has reported the strong herbicidal activity of Artemisia argyi leaf powder (AALP), indicating its high potential for use as an environmentally friendly weed management solution for ecological agriculture. However, AALP's impacts on soil physicochemical properties and microbial communities have remained uninvestigated. This study explores these effects through pot experiments assessing the AALP's efficacy in weed suppression and its ability to promote the growth of Pinellia ternata, a plant utilized in traditional Chinese medicine. The results demonstrate that a 10% concentration of AALP suppressed nearly 100% of all weeds. Additionally, AALP treatments at 2.5%, 5%, 7.5%, and 10% concentrations increased P. ternata yields by 29.79%, 24.76%, 35.67%, and 31.00%, respectively. A soil analysis revealed that AALP enhanced soil fertility by increasing the contents of nutrients such as SOM, AN, AP, AK, Ca, Fe, Mn, and Zn, as well as the enzyme activity of CAT, ACP, UE, and SC, creating an optimal growth environment for P. ternata. In addition, AALP significantly increased the PA (phenolic acid) content in soil, which is a key factor in inhibiting weed germination and growth. Furthermore, a microbial community structure analysis indicated an enrichment of Actinobacteriota and Bacteroidota after AALP treatment, with notable increases in the growth-promoting bacteria Sphingobium and Flavobacterium. A permutational multivariate analysis of variance (PERMANOVA) based on the Bray-Curtis distance reaveled that all of the tested soil properties were significantly correlated with changes in bacterial community composition except for pH. Further two-factor correlation network analysis identified AN, Zn, SC, and PA as key environmental factors. Finally, the Sphingobium sp. strain AFR15, isolated from AALP-treated soil, exhibited significant growth-promoting effects on P. ternata. After inoculation with Sphingobium sp. strain AFR15 for one month, the heights of P. ternata were increased significantly. The leaf length and leaf width of P. ternata were also positively correlated with the treatment concentration of AFR15, and the chlorophyll contents of the leaves also increased. This results highlighted Sphingobium sp. strain AFR15's potential as a specialized microbial fertilizer in crop yield increased. In conclusion, AALP applications not only control weeds but also promote P. ternata growth by improving soil physiochemical properties and fostering beneficial bacterial allies. These findings lay the groundwork for future research and promote the use of AALP in ecological agriculture.

Less is more: A new strategy combining nanomaterials and PGPB to promote plant growth and phytoremediation in contaminated soil

Novel combination strategies of nanomaterials (NMs) and plant growth-promoting bacteria (PGPB) may facilitate soil remediation and plant growth. However, the efficiency of the NM-PGPB combination and interactions among NMs, PGPB, and plants are still largely unknown. We used multiwalled carbon nanotubes (MWCNTs) and zero-valent iron (nZVI) combined with Bacillus sp. PGP5 to enhance the phytoremediation efficiency of Solanum nigrum on heavy metal (HM)-contaminated soil. The NM-PGPB combination showed the best promoting effect on plant growth, which also had synergistic effects on the bioaccumulation of HMs in S. nigrum. The MWCNT-PGP5 combination increased the Cd, Pb, and Zn removal efficiency of S. nigrum by 62.03%, 69.44%, and 61.31%, respectively. The underlining causes of improved plant growth and phytoremediation by NMs-PGPB combination were further elucidated. NM application promoted PGPB survival in soil. Compared with each single application, the combined application minimized disturbance to plant transcription levels and rhizosphere microbial community, resulting in the best performance on soil remediation and plant growth. The NM-PGPB-induced changes in the microbial community and root gene expression were necessary for plant growth promotion. This work reveals the "less is more" advantage of the NM-PGPB combination in soil remediation, providing a new strategy for soil management.

Sphingobium cyanobacteriorum sp. nov., isolated from fresh water

A novel Gram-stain-negative, yellow-pigmented, short rod-shaped bacterial strain, HBC34T, was isolated from a freshwater sample collected from Daechung Reservoir, Republic of Korea. The results of 16S rRNA gene sequence analysis indicated that HBC34T was affiliated with the genus Sphingobium and shared the highest sequence similarity to the type strains of Sphingobium vermicomposti (98.01 %), Sphingobium psychrophilum (97.87 %) and Sphingobium rhizovicinum (97.59 %). The average nucleotide identity (ANI) and digital DNA-DNA hybridisation (dDDH) values between HBC34T and species of the genus Sphingobium with validly published names were below 84.01 and 28.1 %, respectively. These values were lower than the accepted species-delineation thresholds, supporting its recognition as representing a novel species of the genus Sphingobium. The major fatty acids (>10 % of the total fatty acids) were identified as summed feature 8 (C18 : 1ω7c and/or C18 : 1ω6c) and summed feature 3 (C16 : 1ω7c and/or C16 : 1ω6c). The main polar lipids were phosphatidylglycerol, phosphatidylcholine, phosphatidylethanolamine, two phospholipids and two unidentified polar lipids. The respiratory quinone was Q-10. The genomic DNA G+C content of HBC34T was 64.04 %. The polyphasic evidence supports the classification of HBC34T as the type strain of a novel species of the genus Sphingobium, for which the name Sphingobium cyanobacteriorum sp. nov is proposed. The type strain is HBC34T (= KCTC 8002T= LMG 33140T).

Comparative genomics of the plant-growth promoting bacterium Sphingobium sp. strain AEW4 isolated from the rhizosphere of the beachgrass Ammophila breviligulata

Background

The genus Sphingobium within the class Alpha-proteobacteria contains a small number of plant-growth promoting rhizobacteria (PGPR), although it is mostly comprised of organisms that play an important role in biodegradation and bioremediation in sediments and sandy soils. A Sphingobium sp. isolate was obtained from the rhizosphere of the beachgrass Ammophila breviligulata with a variety of plant growth-promoting properties and designated as Sphingobium sp. strain AEW4.

Results

Analysis of the 16S rRNA gene as well as full genome nucleotide and amino acid identities revealed that this isolate is most similar to Sphingobium xenophagum and Sphingobium hydrophobicum. Comparative genomics analyses indicate that the genome of strain AEW4 contains unique features that explain its relationship with a plant host as a PGPR, including pathways involved in monosaccharide utilization, fermentation pathways, iron sequestration, and resistance to osmotic stress. Many of these unique features are not broadly distributed across the genus. In addition, pathways involved in the metabolism of salicylate and catechol, phenyl acetate degradation, and DNA repair were also identified in this organism but not in most closely related organisms.

Conclusion

The genome of Sphingobium sp. strain AEW4 contains a number of distinctive features that are crucial to explain its role as a plant-growth promoting rhizobacterium, and comparative genomics analyses support its classification as a relevant Sphingobium strain involved in plant growth promotion of beachgrass and other plants.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-022-08738-8.

Bacterial Endophytes of Spring Wheat Grains and the Potential to Acquire Fe, Cu, and Zn under Their Low Soil Bioavailability

Simple Summary

Unmasking the overall endophytic bacteria communities from wheat grains may help to identify and describe the microbial colonization of bread and emmer varieties, their link to the bioactive compounds produced, and their possible role in mineral nutrition. The possibility of using microorganisms to improve the microelemental composition of grain is an important food security concern, as approximately one-third of the human population experiences latent starvation caused by Fe (anemia), Zn, or Cu deficiency. Four wheat varieties from T. aestivum L. and T. turgidum subsp. dicoccum were grown in field conditions with low bioavailability of microelements in the soil. Varietal differences in the yield, yield characteristics, and the grain micronutrient concentrations were compared with the endophytic bacteria isolated from the grains. Twelve different bacterial isolates were obtained that represented the genera Staphylococcus, Pantoea, Sphingobium, Bacillus, Kosakonia, and Micrococcus. All studied strains were able to synthesize indole-related compounds (IRCs) with phytohormonal activity. IRCs produced by the bacterial genera Pantoea spp. and Bacillus spp. isolated from high-yielding Oksamyt myronivs’kyi and Holikovs’ka grains may be considered as one of the determinants of the yield of wheat and its nutritional characteristics.

Abstract

Wheat grains are usually low in essential micronutrients. In resolving the problem of grain micronutritional quality, microbe-based technologies, including bacterial endophytes, seem to be promising. Thus, we aimed to (1) isolate and identify grain endophytic bacteria from selected spring wheat varieties (bread Oksamyt myronivs’kyi, Struna myronivs’ka, Dubravka, and emmer Holikovs’ka), which were all grown in field conditions with low bioavailability of microelements, and (2) evaluate the relationship between endophytes’ abilities to synthesize auxins and the concentration of Fe, Zn, and Cu in grains. The calculated biological accumulation factor (BAF) allowed for comparing the varietal ability to uptake and transport micronutrients to the grains. For the first time, bacterial endophytes were isolated from grains of emmer wheat T. turgidum subsp. dicoccum. Generally, the 12 different isolates identified in the four varieties belonged to the genera Staphylococcus, Pantoea, Sphingobium, Bacillus, Kosakonia, and Micrococcus (NCBI accession numbers: MT302194—MT302204, MT312840). All the studied strains were able to synthesize the indole-related compounds (IRCs; max: 16.57 µg∙mL⁻¹) detected using the Salkowski reagent. The IRCs produced by the bacterial genera Pantoea spp. and Bacillus spp. isolated from high-yielding Oksamyt myronivs’kyi and Holikovs’ka grains may be considered as one of the determinants of the yield of wheat and its nutritional characteristics.

Description of Sphingobium psychrophilum sp. nov., a cold-adapted bacterium isolated from Arctic soil

A yellow-coloured, Gram-stain-negative, non-sporulating, psychrotolerant and motile bacterium, designated AR-3-1^T, was isolated from the Arctic soil of Cambridge Bay, Nunavut, Canada. Strain AR-3-1^T could grow at 4-32 °C and pH 5.0- 11.0. Phylogenetic analysis based on its 16S rRNA gene sequence indicated that strain AR-3-1^T formed a lineage within the family Sphingomonadaceae and clustered as a member of the genus Sphingobium. The closest members within this genus were Sphingobium cupriresistens CU4^T (98.1 % sequence similarity), Sphingobium vermicomposti VC-230^T (97.6 %) and Sphingobium lactosutens DS20^T (97.5 %). The only respiratory quinone was the ubiquinone Q-10. Spermidine was the predominant polyamine. The principal cellular fatty acids were summed feature 8 (C_18 : 1  ω7c and/or C_18 : 1  ω6c), summed feature 3 (iso-C_{15  : 0} 2-OH and/or C_{16  : 1} ω7c), C_16 : 0 and C_14 : 0 2-OH. The major polar lipids were phosphatidylethanolamine, phosphatidylmonomethylethanolamine, phosphatidyldimethylethanolamine, diphosphatidylglycerol, phosphatidylglycerol, sphingoglycolipid and phosphoglycolipid. The DNA G+C content was 63.1 %. The average nucleotide identity and in silico DNA-DNA hybridization relatedness values between strain AR-3-1^T and its most closely related genus members were ≤89.6 and 39.6 %, respectively. The genome was 5 162 327 bp long, with 83 scaffolds and 4824 protein-coding genes. The genome showed six putative biosynthetic gene clusters responsible for various secondary metabolites. Based on this polyphasic study, strain AR-3-1^T represents a novel species within the genus Sphingobium, for which the name Sphingobium psychrophilum sp. nov. is proposed. The type strain is AR-3-1^T (=KACC 21613^T=NBRC 114604^T).

Testing the Two-Step Model of Plant Root Microbiome Acquisition Under Multiple Plant Species and Soil Sources

The two-step model for plant root microbiomes considers soil as the primary microbial source. Active selection of the plant’s bacterial inhabitants results in a biodiversity decrease toward roots. We collected sixteen samples of in situ ruderal plant roots and their soils and used these soils as the main microbial input for single genotype tomatoes grown in a greenhouse. Our main goal was to test the soil influence in the structuring of rhizosphere microbiomes, minimizing environmental variability, while testing multiple plant species. We massively sequenced the 16S rRNA and shotgun metagenomes of the soils, in situ plants, and tomato roots. We identified a total of 271,940 bacterial operational taxonomic units (OTUs) within the soils, rhizosphere and endospheric microbiomes. We annotated by homology a total of 411,432 (13.07%) of the metagenome predicted proteins. Tomato roots did follow the two-step model with lower α-diversity than soil, while ruderal plants did not. Surprisingly, ruderal plants are probably working as a microenvironmental oasis providing moisture and plant-derived nutrients, supporting larger α-diversity. Ruderal plants and their soils are closer according to their microbiome community composition than tomato and its soil, based on OTUs and protein comparisons. We expected that tomato β-diversity clustered together with their soil, if it is the main rhizosphere microbiome structuring factor. However, tomato microbiome β-diversity was associated with plant genotype in most samples (81.2%), also supported by a larger set of enriched proteins in tomato rhizosphere than soil or ruderals. The most abundant bacteria found in soils was the Actinobacteria Solirubrobacter soli, ruderals were dominated by the Proteobacteria Sphingomonas sp. URGHD0057, and tomato mainly by the Bacteroidetes Ohtaekwangia koreensis, Flavobacterium terrae, Niastella vici, and Chryseolinea serpens. We calculated a metagenomic tomato root core of 51 bacterial genera and 2,762 proteins, which could be the basis for microbiome-oriented plant breeding programs. We attributed a larger diversity in ruderal plants roots exudates as an effect of the moisture and nutrient acting as a microbial harbor. The tomato and ruderal metagenomic differences are probably due to plant domestication trade-offs, impacting plant-bacteria interactions.

Isolation and characterization of a novel Sphingobium yanoikuyae strain variant that uses biohazardous saturated hydrocarbons and aromatic compounds as sole carbon sources

Background: Green micro-alga, Chlamydomonas reinhardtii (a Chlorophyte), can be cultured in the laboratory heterotrophically or photo-heterotrophically in Tris- Phosphate- Acetate (TAP) medium, which contains acetate as the carbon source. Chlamydomonas can convert acetate in the TAP medium to glucose via the glyoxylate cycle, a pathway present in many microbes and higher plants. A novel bacterial strain, CC4533, was isolated from a contaminated TAP agar medium culture plate of a Chlamydomonas wild type strain. In this article, we present our research on the isolation, and biochemical and molecular characterizations of CC4533.

Methods: We conducted several microbiological tests and spectrophotometric analyses to biochemically characterize CC4533. The 16S rRNA gene of CC4533 was partially sequenced for taxonomic identification. We monitored the growth of CC4533 on Tris-Phosphate (TP) agar medium (lacks a carbon source) containing different sugars, aromatic compounds and saturated hydrocarbons, to see if CC4533 can use these chemicals as the sole source of carbon.

Results: CC4533 is a Gram-negative, non-enteric yellow pigmented, aerobic, mesophilic bacillus. It is alpha-hemolytic and oxidase-positive. CC4533 can ferment glucose, sucrose and lactose, is starch hydrolysis-negative, resistant to penicillin, polymyxin B and chloramphenicol. CC4533 is sensitive to neomycin. Preliminary spectrophotometric analyses indicate that CC4533 produces b-carotenes. NCBI-BLAST analyses of the partial 16S rRNA gene sequence of CC4533 show 99.55% DNA sequence identity to that of Sphingobium yanoikuyae strain PR86 and S. yanoikuyae strain NRB095. CC4533 can use cyclo-chloroalkanes, saturated hydrocarbons present in car motor oil, polyhydroxyalkanoate, and mono- and poly-cyclic aromatic compounds, as sole carbon sources for growth.

Conclusions: Taxonomically, CC4533 is very closely related to the alpha-proteobacterium S. yanoikuyae, whose genome has been sequenced. Future research is needed to probe the potential of CC4533 for environmental bioremediation. Whole genome sequencing of CC4533 will confirm if it is a novel strain of S. yanoikuyae or a new Sphingobium species.

Sphingobium pinisoli sp. nov., isolated from the rhizosphere soil of a Korean native pine tree

A Gram-stain negative, aromatic compound degrading bacterium, designated strain ASA28^T, was isolated from the rhizosphere soil of a pine tree at Anmyon island, Taean in Korea. Strain ASA28^T was found to be strictly aerobic, non-motile, short rods which can grow at 15-28 °C (optimum, 25-28 °C), at pH 5.0-11.0 (optimum, pH 7.0) and at salinities of 0-1.0% (w/v) NaCl (optimum, 0% NaCl). Phylogenetic analyses based on 16S rRNA gene sequences indicated that strain ASA28^T belongs to the genus Sphingobium, showing high sequence similarity to Sphingobium scionense WP01^T (97.8%), Sphingobium vermicocomposti VC-230^T (96.8%), Sphingobium yanoikuyae ATCC 51230^T (96.5%) and Sphingobium herbicidovorans MH^T (95.6%). The predominant ubiquinone and polyamine components were identified as Q-10 and spermidine, respectively. The major fatty acids were identified as C_18:1ω7c, C_16:0, C_14:0 2-OH and C_16:1ω7c and/or C_15:0 iso 2-OH. The major polar lipids were identified as diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, phosphatidylmonomethylethanolamine, phosphatidylcholine, sphingoglycolipid, phosphoglycolipid, four unidentified aminophospholipids, an unidentified aminolipid, two unidentified phospholipids and six unidentified lipids. The DNA G+C content of this novel isolate was determined to be 63.0 mol%. DNA-DNA relatedness between strain ASA28^T and S. herbicidovorans KCTC 2939^T, S. vermicocomposti DSM 21299^T and S. scionense DSM 19371^T was determined to be 32 ± 5%, 30 ± 4% and 25 ± 5%, respectively. On the basis of the phylogenetic, phenotypic and chemotaxonomic analyses in this study, strain ASA28^T is considered to represent a novel species of the genus Sphingobium, for which the name Sphingobium pinisoli sp. nov. is proposed. The type strain is ASA28^T (= KACC 18700^T = NBRC 112246^T).

Sphingobium soli sp. nov. isolated from rhizosphere soil of a rose

Strain THG-SQA7(T), a Gram-negative, strictly aerobic, non-motile, rod-shaped bacterium was isolated from rhizosphere soil of a rose in PR China. Strain THG-SQA7(T) is closely related to the members of the genus Sphingobium, showing the highest 16S rRNA gene sequence similarities with Sphingobium lactosutens KACC 18100(T) (98.2%) and Sphingobium abikonense KCTC 2864(T) (98.1%). The DNA-DNA relatedness between strain THG-SQA7(T) and S. lactosutens KACC 18100(T) and S. abikonense KCTC 2864(T) was 26.2 ± 0.9 and 28.3 ± 1.2%, respectively. Chemotaxonomic data showed that strain THG-SQA7(T) possesses ubiquinone Q-10 as the predominant respiratory quinone, and C(18:1)ω7c, C(16:0), summed feature 3 (C(16:1)ω7c and/or C(16:1)ω6c) and C(14:0) 2OH as the major fatty acids. The major polar lipids were found to be phosphatidylethanolamine, phosphatidylmonomethylethanolamine, phosphatidylglycerol, sphingoglycolipid, diphosphatidylglycerol and phosphatidyldimethylethanolamine. Based on these results, together with phenotypic characterization, a novel species, Sphingobium soli sp. nov. is proposed.with the type strain is THG-SQA7(T) (=CCTCC AB 2015125(T) = KCTC 42607(T)).

Cold-Active, Heterotrophic Bacteria from the Highly Oligotrophic Waters of Lake Vanda, Antarctica

The permanently ice-covered lakes of the McMurdo Dry Valleys, Antarctica are distinctive ecosystems that consist strictly of microbial communities. In this study, water samples were collected from Lake Vanda, a stratified Dry Valley lake whose upper waters (from just below the ice cover to nearly 60 m) are highly oligotrophic, and used to establish enrichment cultures. Six strains of psychrotolerant, heterotrophic bacteria were isolated from lake water samples from a depth of 50 or 55 m. Phylogenetic analyses showed the Lake Vanda strains to be species of Nocardiaceae, Caulobacteraceae, Sphingomonadaceae, and Bradyrhizobiaceae. All Lake Vanda strains grew at temperatures near or below 0 °C, but optimal growth occurred from 18 to 24 °C. Some strains showed significant halotolerance, but no strains required NaCl for growth. The isolates described herein include cold-active species not previously reported from Dry Valley lakes, and their physiological and phylogenetic characterization broadens our understanding of these limnologically unique lakes.

Sphingobium barthaii sp. nov., a high molecular weight polycyclic aromatic hydrocarbon-degrading bacterium isolated from cattle pasture soil

A Gram-stain-negative, yellow, rod-shaped bacterium, designated strain KK22(T), was isolated from a microbial consortium that grew on diesel fuel originally recovered from cattle pasture soil. Strain KK22(T) has been studied for its ability to biotransform high molecular weight polycyclic aromatic hydrocarbons. On the basis of 16S rRNA gene sequence phylogeny, strain KK22(T) was affiliated with the genus Sphingobium in the phylum Proteobacteria and was most closely related to Sphingobium fuliginis TKP(T) (99.8%) and less closely related to Sphingobium quisquiliarum P25(T) (97.5%). Results of DNA-DNA hybridization (DDH) revealed relatedness values between strain KK22(T) and strain TKP(T) and between strain KK22(T) and strain P25(T) of 21 ± 4% (reciprocal hybridization, 27 ± 2%) and 15 ± 2% (reciprocal hybridization, 17 ± 1%), respectively. Chemotaxonomic analyses of strain KK22(T) showed that the major respiratory quinone was ubiquinone Q-10, that the polar lipid profile consisted of phosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine, phosphatidyl-N-methylethylethanolamine and sphingoglycolipid, and that C18 : 1ω7c and C14 : 0 2-OH were the main fatty acid and hydroxylated fatty acids, respectively. This strain was unable to reduce nitrate and the genomic DNA G+C content was 64.7 mol%. Based upon the results of the DDH analyses, the fact that strain KK22(T) was motile, and its biochemical and physiological characteristics, strain KK22(T) could be separated from recognized species of the genus Sphingobium. We conclude that strain KK22(T) represents a novel species of this genus for which the name Sphingobium barthaii sp. nov. is proposed; the type strain is KK22(T) ( = DSM 29313(T) = JCM 30309(T)).

Sphingobium sufflavum sp. nov., isolated from a freshwater lake

A Gram-stain negative, rod-shaped, non-motile, non-spore-forming and aerobic bacterial strain, designated HL-25T, was isolated and characterized in a taxonomic study using a polyphasic approach. Comparative analysis of the 16S rRNA gene sequences showed that the isolate constituted a distinct branch within the genus Sphingobium , showing the highest level of 16S rRNA gene sequence similarity to Sphingobium vulgare HU1-GD12T (96.6 %). The major fatty acids (>10 %) of strain HL-25T were C18 : 1ω7c, C16 : 0, summed feature 3 (comprising C16 : 1ω7c and/or C16 : 1ω6c) and C18 : 0. The major cellular hydroxy fatty acid was C14 : 0 2-OH. The major isoprenoid quinone was Q-10 and the DNA G+C content was 63.8 mol%. The polar lipid profile consisted of a mixture of sphingoglycolipid, phosphatidylglycerol, phosphatidylethanolamine, phosphatidyldimethylethanolamine, diphosphatidylglycerol, an uncharacterized glycolipid, an uncharacterized aminophospholipid and four uncharacterized phospholipids. The polyamine pattern of strain HL-25T contained spermidine and putrescine. On the basis of these genotypic, chemotaxonomic and phenotypic data, strain HL-25T represents a novel species in the genus Sphingobium , for which the name Sphingobium sufflavum sp. nov. is proposed. The type strain is HL-25T ( = BCRC 80413T = KCTC 23953T).

Sphingobium cupriresistens sp. nov., a copper-resistant bacterium isolated from copper mine soil, and emended description of the genus Sphingobium

A Gram-negative, aerobic, copper-resistant bacterium, designated strain CU4T, was isolated from copper mine soil in Daye, China. Phylogenetic analysis based on 16S rRNA gene sequences showed highest similarity to Sphingobium rhizovicinum CC-FH12-1T (98.4 %), followed by Sphingobium francense Sp+T (97.2 %), Sphingobium japonicum UT26T (97.1 %), Sphingobium abikonense NBRC 16140T (97.0 %), Sphingobium xenophagum DSM 6383T (96.9 %) and Sphingobium yanoikuyae DSM 7462T (95.5 %). The major fatty acids (>5 %) were summed feature 7 (C18 : 1ω7c, C18 : 1ω9t and/or C18 : 1ω12t), summed feature 4 (C16 : 1ω7c and/or iso-C15 : 0 2-OH), C16 : 0 and C14 : 0 2-OH, and the predominant quinone was ubiquinone Q-10. Spermidine was the major polyamine component. The major polar lipids were diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, sphingoglycolipid, phosphatidyldimethylethanolamine and phosphatidylcholine. The genomic DNA G+C content of strain CU4T was 64.9 mol%. Comparison of DNA–DNA hybridization, phenotypic and chemotaxonomic characteristics between strain CU4T and phylogenetically related strains revealed that the new isolate represents a novel species of the genus Sphingobium , for which the name Sphingobium cupriresistens sp. nov. is proposed. The type strain is CU4T ( = KCTC 23865T = CCTCC AB 2011146T). An emended description of the genus Sphingobium is also proposed.

Sphingobium czechense sp. nov., isolated from a hexachlorocyclohexane dump site

A yellow-pigmented bacterial strain, designated LL01T, was isolated from hexachlorocyclohexane (HCH)-contaminated soil at Spolana Neratovice, a former Czech producer of lindane. A neighbour-joining tree based on 16S rRNA gene sequences showed that strain LL01T occupied a distinct phylogenetic position in the Sphingobium cluster, showing highest similarity to Sphingobium rhizovicinum CC-FH12-1T (98.5 %). The DNA G+C content of strain LL01T was 66.1 mol%. The predominant respiratory pigment was ubiquinone Q-10. The polar lipid profile of strain LL01T also corresponded to those reported for other Sphingobium species (phosphatidylethanolamine, diphosphatidylglycerol, phosphatidylcholine, phosphatidylglycerol, phosphatidylmonomethylethanolamine, phosphatidyldimethylethanolamine, sphingoglycolipids), supporting its identification as a member of the genus Sphingobium . Spermidine was the major polyamine observed. The results obtained from DNA–DNA hybridization and biochemical and physiological tests clearly distinguished strain LL01T from closely related species of the genus Sphingobium . Therefore, strain LL01T represents a novel species of the genus Sphingobium , for which the name Sphingobium czechense sp. nov. is proposed (type strain LL01T = CCM 7979T = DSM 25410T).

Protection of Arabidopsis thaliana against leaf-pathogenic Pseudomonas syringae by Sphingomonas strains in a controlled model system

Diverse bacterial taxa live in association with plants without causing deleterious effects. Previous analyses of phyllosphere communities revealed the predominance of few bacterial genera on healthy dicotyl plants, provoking the question of whether these commensals play a particular role in plant protection. Here, we tested two of them, Methylobacterium and Sphingomonas, with respect to their ability to diminish disease symptom formation and the proliferation of the foliar plant pathogen Pseudomonas syringae pv. tomato DC3000 on Arabidopsis thaliana. Plants were grown under gnotobiotic conditions in the absence or presence of the potential antagonists and then challenged with the pathogen. No effect of Methylobacterium strains on disease development was observed. However, members of the genus Sphingomonas showed a striking plant-protective effect by suppressing disease symptoms and diminishing pathogen growth. A survey of different Sphingomonas strains revealed that most plant isolates protected A. thaliana plants from developing severe disease symptoms. This was not true for Sphingomonas strains isolated from air, dust, or water, even when they reached cell densities in the phyllosphere comparable to those of the plant isolates. This suggests that plant protection is common among plant-colonizing Sphingomonas spp. but is not a general trait conserved within the genus Sphingomonas. The carbon source profiling of representative isolates revealed differences between protecting and nonprotecting strains, suggesting that substrate competition plays a role in plant protection by Sphingomonas. However, other mechanisms cannot be excluded at this time. In conclusion, the ability to protect plants as shown here in a model system may be an unexplored, common trait of indigenous Sphingomonas spp. and may be of relevance under natural conditions.

Biochemical characterization of a sphingomonad isolate from the ascocarp of white truffle (Tuber magnatum Pico)

Available information on bacteria that influence the economically important white truffle (Tuber magnatum Pico) life cycle is scarce. From the ascocarp of white truffle we isolated a strain TMG 022C, capable for growth in nitrogendepleted conditions and assimilation of mannitol and trehalose. According to 16S rDNA sequence phylogeny, the strain was closely related to Sphingobium amiense. The strain had the ability to perform ammonification, reduce nitrate and solubilize Ca3(PO4)2, produce chitinase, lipase, phospholipase and ?-glucanase, but not cellulase, pectinase, protease and siderophores. The results suggest that Sphingobium sp. TMG 022C could have an influence on the Tuber magnatum life cycle through improved mycelium nutrition and ascocarp decomposition.

Sphingobium faniae sp. nov., a pyrethroid-degrading bacterium isolated from activated sludge treating wastewater from pyrethroid manufacture

A bacterial strain capable of degrading pyrethroid, designated JZ-2T, was isolated from activated sludge treating pyrethroid-contaminated wastewater. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain JZ-2T belongs to the genus Sphingobium. It showed the highest levels of 16S rRNA gene sequence similarity to Sphingobium cloacae JCM 10874T (98.3 %) and Sphingobium ummariense CCM 7431T (97.1 %), and 94.8–96.9 % similarity to the type strains of other members of the genus Sphingobium. Strain JZ-2T contained C18 : 1 ω7c as the predominant fatty acid, C14 : 0 2-OH as the major 2-hydroxy fatty acid, ubiquinone Q-10 as the main respiratory quinone, diphosphatidylglycerol, phosphatidylglycerol, phosphatidylcholine, phosphatidylmonomethylethanolamine, phosphatidylethanolamine and two sphingoglycolipids as the predominant polar lipids and spermidine as the major polyamine. DNA–DNA hybridization results showed that strain JZ-2T had low genomic relatedness with S. cloacae JCM 10874T (34 %) and S. ummariense CCM 7431T (23 %). Based on the phenotypic, genotypic and phylogenetic data presented, strain JZ-2T is considered to represent a novel species of the genus Sphingobium, for which the name Sphingobium faniae sp. nov. is proposed. The type strain is JZ-2T (=CGMCC 1.7749T =DSM 21829T).

Sphingobium scionense sp. nov., an aromatic hydrocarbon-degrading bacterium isolated from contaminated sawmill soil

This study characterized strain WP01T, a Gram-staining-negative, rod-shaped, aerobic bacterium isolated from a polycyclic aromatic hydrocarbon-contaminated soil in New Zealand. Strain WP01T shared many characteristics of the genus Sphingobium: the predominant respiratory quinone (89 %) was ubiquinone with ten isoprene units (Q-10); the major fatty acids were C18 : 1 ω7c, C16 : 1 ω7c, C16 : 0 and C14 : 0 2-OH; spermidine was the major polyamine; the DNA G+C content was 63.8 mol%; and the Sphingobium-specific 16S rRNA signatures were conserved. A point of difference from other species of the genus Sphingobium was that strain WP01T reduced nitrate to nitrite. The polar lipid pattern consisted of the predominant compounds diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol and sphingoglycolipids. 16S rRNA gene sequence analysis showed that, amongst the recognized species of the genus Sphingobium, strain WP01T was most similar to Sphingobium yanoikuyae GIFU 9882T and Sphingobium amiense YTT (>97 % 16S rRNA gene sequence similarities). The low DNA–DNA relatedness values between strain WP01T and S. yanoikuyae GIFU 9882T (46.6 %) and S. amiense DSM 16289T (25.6 %) indicated no relatedness at the species level. On the basis of these characteristics, it is concluded that strain WP01T should be considered as representing a novel species within the genus Sphingobium, for which the name Sphingobium scionense sp. nov. is proposed. The type strain is WP01T (=DSM 19371T=ICMP 13533T).

Sphingobium vulgare sp. nov., isolated from freshwater sediment

A Gram-negative, motile, non-spore-forming bacterial strain, designated HU1-GD12(T), was isolated from freshwater sediment. The strain was characterized by using a polyphasic approach in order to determine its taxonomic position. Comparative analysis of the 16S rRNA gene sequence showed that the isolate constituted a distinct branch within the genus Sphingobium, showing the highest level of sequence similarity with respect to Sphingobium ummariense RL-3(T) (96.2 %). Strain HU1-GD12(T) had a genomic DNA G+C content of 66.8 mol% and Q-10 as the predominant respiratory quinone. Furthermore, the major polyamine component (spermidine) in the cytoplasm and the presence of sphingoglycolipids suggested that strain HU1-GD12(T) belonged to the family Sphingomonadaceae. On the basis of its phenotypic properties and phylogenetic distinctiveness, strain HU1-GD12(T) represents a novel species of the genus Sphingobium, for which the name Sphingobium vulgare sp. nov. is proposed. The type strain is HU1-GD12(T) (=LMG 24321(T)=KCTC 22289(T)).