Biotransformation of benzoin by Sphingomonas sp. LK11 and ameliorative effects on growth of Cucumis sativus

Plant endophytes play vital role in plant growth promotion as well as in abiotic and biotic stress tolerance. They also mediate biotransformation of complex organic materials to simpler and useful by-product. Therefore, the role of plant endophyte in plant growth promotion and stress tolerance has gained considerable attention in recent days. Sphingomonas sp. LK11 is an important plant endophyte that actively regulates plant growth. However, the biotransformation and stress tolerance potential of Sphingomonas sp. LK11 was yet to be elucidated. Therefore, we studied the biotransformation of benzoin by Sphingomonas sp. LK11. We found that, Sphingomonans sp. LK11 biotransformed benzoin to benzamide. Further application of benzamide to Cucumis sativus led to decrease in agronomic potential of C. sativus as benzamide acts as an abiotic stress agent. However, the application of Sphingomonas sp. LK11 inoculums with benzamide reverted back the agronomic trait of the plants, suggesting the role of Sphingomonas sp. LK11 in biotransformation and abiotic stress tolerance in plants.

Sphingomonas tabacisoli sp. nov., a member of the genus Sphingomonas, isolated from rhizosphere soil of Nicotiana tabacum L

A Gram-staining-negative, aerobic, motile and rod-shaped bacterium, designated strain X1-8T, was isolated from rhizosphere soil of Nicotiana tabacum L. collected from the tobacco produce base located in Kunming, south-west PR China. Cells showed oxidase-negative and catalase-positive reactions and were motile by means of peritrichous flagella. Growth occurred at 25-40 °C and pH 6.0-8.0 with optimal growth at 30-35 °C, pH 7.0. The major respiratory lipoquinone was Q-10. C16 : 0 and summed feature 8 (C18 : 1ω7c and/or C18 : 1ω6c) were identified as major cellular fatty acids. The profile of polar lipids contained diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, phosphatidylmethylethanolamine, sphingoglycolipid, phosphatidylcholine and one unidentified glycolipid. The major polyamine was sym-homospermidine. The genomic DNA G+C content was 66.5 mol%. The results of phylogenetic analysis based on 16S rRNA gene sequences indicated that X1-8T should be affiliated to the genus Sphingomonasand formed a clade with most closely related species Sphingomonas changbaiensisNBRC 104936T. The results of 16S rRNA gene sequences similarity analysis indicated that X1-8T had the highest similarity with S. changbaiensisNBRC 104936T (98.4 %) and lower than 96.0 % with other species of the genus Sphingomonas. DNA-DNA hybridization data indicated that X1-8T represented a novel genomic species of the genus Sphingomonas. The characteristics determined in the polyphasic taxonomic study indicated that X1-8T represents a novel species of the genus Sphingomonas, for which the name Sphingomonas tabacisoli sp. nov. (type strain X1-8T=KCTC 62032T=CGMCC 1.16275T) is proposed.

Sphingomonas montis sp. nov., Isolated from Forest Soil of Low-Altitude Mountain

Strain DRJ-4^T was isolated from forest soil of a low-altitude mountain and was taxonomically characterized by a polyphasic approach. This strain was yellow-colored, Gram-stain-negative, strictly aerobic, motile, non-sporulating, catalase-positive, oxidase-negative, and rod-shaped. Strain DRJ-4^T was able to grow at 20-42 °C, pH 6.5-10.0, and 0-1.0% (w/v) NaCl concentration. Based on the 16S rRNA gene sequence analysis, strain DRJ-4^T formed a distinct lineage within the members of the family Sphingomonadaceae of the phylum Proteobacteria and moderately related to Sphingomonas faucium E62-3^T (96.67% sequence similarity), 'Sphingosinicella ginsenosidimutans' BS11 (96.45% sequence similarity), Sphingosinicella vermicomposti YC7378^T (96.27% sequence similarity), and Sphingobium boeckii 469^T (95.82% sequence similarity). The sole respiratory quinone was ubiquinone Q-10 and the major polyamine was homospermidine. The polar lipid profile revealed the presence of phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol, phosphatidylcholine, phosphatidylmonomethylethanolamine, and sphingoglycolipid. The predominant fatty acids of strain DRJ-4^T were summed feature 8 (C_18:1ω7c and/or C_18:1ω6c), summed feature 3 (C_16:1ω7c and/or C_16:1ω6c), C_16:0, and C_17:1ω6c. The genomic DNA G + C was 64.0 mol %. On the basis of phenotypic, genotypic, and phylogenetic analysis, strain DRJ-4^T represents a novel species of the genus Sphingomonas, for which the name Sphingomonas montis sp. nov. is proposed. The type strain of Sphingomonas montis is DRJ-4^T (= KEMB 9005-708^T = NBRC 113142^T).

Sphingomonas colocasiae sp. nov., isolated from taro (Colocasia esculanta)

A polyphasic approach was used to characterize an aerobic, Gram-stain-negative, rod-shaped bacterium (designed as strain CC-MHH0539^T) isolated from the chopped tuber of taro (Colocasia esculanta) in Taiwan. Strain CC-MHH0539^T was able to grow at 15-30 °C (optimum, 25 °C), at pH 6.0-9.0 (optimum, 7.0) and with 0-1 % (w/v) NaCl. Strain CC-MHH0539^T showed highest 16S rRNA gene sequence similarity to Sphingomonas laterariae LNB2^T (96.8 %), Sphingobium boeckii 469^T (96.5 %), Sphingomonas faucium E62-3^T (96.4 %) and Sphingosinicella vermicomposti YC7378^T (96.2 %) and <96.1 % similarity to other sphingomonads. Strain CC-MHH0539^T was found to cluster mainly with the clade that accommodated members of the genus Sphingomonas. The dominant cellular fatty acids were C16 : 0, C16 : 1ω5c, C14 : 0 2-OH, C16 : 1ω7c/C16 : 1ω6c and C18 : 1ω7c/C18 : 1ω6c. Diphosphatidylglycerol, phosphatidylglycerol, phosphatidylcholine, phosphatidylethanolamine, phosphatidylmonomethylethanolamine, two sphingoglycolipids and two unidentified phospholipids were detected in strain CC-MHH0539^T. The DNA G+C content was 69.5 mol%. The respiratory quinone system and predominant polyamine was ubiquinone 10 (Q-10) and sym-homospermidine, respectively, which is in line with Sphingomonas representatives. Based on the distinct phylogenetic, phenotypic and chemotaxonomic traits, strain CC-MHH0539^T is considered to represent a novel species of the genus Sphingomonas, for which the name Sphingomonas colocasiae sp. nov. is proposed. The type strain is CC-MHH0539^T (=BCRC 80933^T=JCM 31229^T).