Cyanate is a low abundance but actively cycled nitrogen compound in soil

Cyanate can serve as a nitrogen and/or carbon source for different microorganisms and as an energy source for autotrophic ammonia oxidizers. However, the extent of cyanate availability and utilisation in terrestrial ecosystems and its role in biogeochemical cycles is poorly known. Here we analyse cyanate concentrations in soils across a range of soil types, land management practices and climates. Soil cyanate concentrations were three orders of magnitude lower than ammonium or nitrate. We determined cyanate consumption in a grassland and rice paddy soil using stable isotope tracer experiments. We find that cyanate turnover was rapid and dominated by biotic processes. We estimated that in-situ cyanate production rates were similar to those associated with urea fertilizer decomposition, a major source of cyanate in the environment. We provide evidence that cyanate is actively turned over in soils and represents a small but continuous nitrogen/energy source for soil microbes.

Sandarakinorhabdus rubra sp. nov., and Sandarakinorhabdus oryzae sp. nov., isolated from oxidized rice paddy soil

Three Gram-stain-negative, motile or non-motile, rod-shaped, facultatively aerobic strains, designated MO-4T, NP-34 and NM-18T, were isolated from oxidized rice paddy soil in Chungbuk, Republic of Korea. Colonies were circular and convex with entire margins, red in colour on R2A after 3 days at 30 °C. The three strains grew at pH 5.0–10.0 (optimum, pH 8.0), at 15–45 °C (optimum, 30 °C) and at salinities of 0–1.5 % (w/v) NaCl (optimum, 0.4 % NaCl). The results of phylogenetic analyses based on 16S rRNA gene sequences indicated that the three isolates represent members of the genus Sandarakinorhabdus and strains MO-4T and NP-34 were most closely related to Sandarakinorhabdus cyanobacteriorum TH057T (97.7 %) and Sandarakinorhabdus limnophila DSM 17366T (97.1 %). NM-18T showed highest 16S rRNA gene sequence similarities to Sandarakinorhabdus limnophila DSM 17366T (98.7 %) and Sandarakinorhabdus cyanobacteriorum TH057T (96.7 %). Genomic similarities between strains MO-4T and NM-18T and the two type strains of species of the genus Sandarakinorhabdus based on average nucleotide identity and digital DNA–DNA hybridization values were lower than the species delineation thresholds. The major fatty acids were iso-C18 : 1 ω7c and summed feature 3. The DNA G+C contents of strains MO-4T and NM-18T, obtained from genome sequencing data, were 67.6 and 66.6 mol%, respectively. On the basis of these genotypic and phenotypic characteristics, the three strains are assigned to two novel species of the genus Sandarakinorhabdus , for which the names Sandarakinorhabdus rubra sp. nov. (type strain MO-4T =KACC 21378=NBRC 114106) and Sandarakinorhabdus oryzae sp. nov. (type strain NM-18T=KACC 21379=NBRC 113957) are proposed.