Background
Kosakonia pseudosacchari is a Gram-negative, plant growth-promoting rhizobacterium, which was first isolated as an endophyte of Zea mays [1] and later from Cyamopsis tetragon [2]. Kosakonia spp. are rarely human pathogens, so that the significant AMR and virulence genes identified in K. cowanii strain 888-76T [3] are uncommon in K. pseudosacchari and the other species. Instead, these are more often noted for carrying plant-beneficial genes such as those enabling phosphate solubilisation or nitrogen fixation. Here, K. pseudosacchari RX.G5M8 was found in soil screened for methylotrophy, a plant-associated trait previously observed in K. arachidis [4].
Method
Bacteria from soil samples were screened for growth in a minimal salts medium [5] containing either 5% v:v methanol or methylammonium chloride at the same molar concentration. After incubation at 27 °C for 7 days with shaking followed by streaking onto Luria agar, selected colonies were passaged to purity on Luria agar before DNA extraction. Complete genomes were generated using the Illumina NovaSeq 6000 and Oxford Nanopore MinION platforms, allowing hybrid assembly via Unicycler v0.4.8-beta.
Results
The RX.G5M8 genome comprises a single chromosome of 4.9 Mbp (53.91% G+C). It contains a tightly clustered Nif regulon, as well as a range of other plant growth-promoting genes including ppdC and ipdC for auxin synthesis and pqqBCDE for phosphate solubilization. A glutathione-dependent formaldehyde detoxification pathway accounts for its tolerance of methanol and numerous genes appear consistent with endophytic colonisation [6].