Complete Genome Sequence of Kosakonia radicincitans GXGL-4A, a Nitrogen-Fixing Bacterium with Capability to Degrade TEX.

Kosakonia radicincitans GXGL-4A, a free-living nitrogen-fixing (NF) bacterial strain isolated from maize (Zea mays L.) roots was found to have ability to degrade aromatic hydrocarbons. In this study, we describe the main morphological characteristics of bacterium, aromatic hydrocarbon-degrading capability, and the complete genome of K. radicincitans GXGL-4A. The genome is consisted of only one 5,687,681 bp linear chromosome with a G + C content of 53.96%. The strain has two genetically distinct nitrogenase systems, one based on molybdenum (Mo) similar to nitrogenase isolated from a wide range of nitrogen-fixing organisms, and the other contains iron (Fe). The differences in transcriptional level of several important nitrogen fixation (nif) genes between LB (nitrogen-rich, NR) and A15 nitrogen-free (nitrogen-limited, NL) culture conditions were detected using Real-time Quantitative Reverse Transcription PCR (qRT-PCR). The bacterial cells of GXGL-4A can grow well in LB liquid medium containing 1% toluene, ethylbenzene or xylene, suggesting a good resistance to the tested aromatic hydrocarbons. The results of GC-MS analysis showed that K. radicincitans GXGL-4A has a good capability to degrade toluene, ethylbenzene, and xylene (TEX). Completion of the genome sequencing will no doubt contribute to the deep exploration and comprehensive utilization of this NF bacterium in sustainable agriculture and bioremediation of aromatic pollutants.