A novel plant-associated thermotolerant alkaliphilic methylotorph of the genus Paracoccus

摘要

Strain GB isolated from the maize rhizosphere is a gram-negative, aerobic, non-sproe-forming, nonpigmented, nonmotile, chemolithotrophic, facultatively methylotrophic bacterium. Cells are cocci or short rods. The strain does not require vitamins. Optimum growth in a medium with methanol occurs at 38-42 deg C at pH 8.0-9.2. The doubling time is 12 h. In addition to methanol, the bacterium can grow on methylamine, dimethylformamide, acetone, thiosulfate + NaHCO_3, and i an atmosphere of H_2 + CO_2 + O_2. Methanol and methylamine are oxidized by the respective dehydrogenases to CO_2 via formaldehyde and formate, respectively. The CO_2 produced is assimilated via the ribulose bisphosphate pathway. Fatty acids are dominated by cyclopropanoic (58-61%), palmitic (24-26%), and octadecanoic (8-9%) acids. The main phospholipids are phosphatidylglycerol, phosphatidylethanolamine, and phosphatidylcholine. The major ubiquinone is Q_10. The bacterial gnome contains genes controlling the synthesis and secretion of cytokininsl. The culture liquid exhibits cytokinin activity. The G+C content of DNA is 62.5 mol %, as determined from the DNA thermal denaturation temperature (T_m). Stari GB shows a moderate degree of DNA-DNA homology (<40%) with the type representatives of the genus Paracoccus. Based on the data obtained, the bacterium was classified as a new species of this genus, named P. kondratievae.