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

Strain GB isolated from the maize rhizosphere is a gram-negative, aerobic, non-spore-forming, nonpigmented, nonmotile, chemolithotrophic, facultativel y 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 degreesC at pH 8.0-9.2. The doubling time is 12 h. In addition to metha nol, the bacterium can grow on methylamine, dimethylformamide, acetone, thi osulfate + NaHCO3, and in an atmosphere of H-2 + CO2 + O-2 Methanol and met hylamine are oxidized by the respective dehydrogenases to CO2 via formaldeh yde and formate, respectively. The CO2 produced is assimilated via the ribu lose bisphosphate pathway. Fatty acids are dominated by cyclopropanoic (58- 61%), palmitic (24-26%), and octadecanoic (8-9%) acids. The main phospholip ids are phosphatidylglycerol, phosphatidylethanolamine, and phosphatidylcho line, The major ubiquinone is Q(10). The bacterial genome contains genes co ntrolling the synthesis and secretion of cytokinins. The culture liquid exh ibits cytokinin activity. The G+C content of DNA is 62.5 mol %, as determin ed from the DNA thermal denaturation temperature (T-m). Strain GB shows a m oderate degree of DNA-DNA homology (<40%) with the type representatives of the genus Paracoccus. Based on the data obtained, the bacterium was classif ied as a new species of this genus, named P. kondratievae.