Metabolic comparisons between M. flagellatus (beta-proteobacteria) and Methylobacterium extorquens (alpha-proteobacteria) indicated that these species utilize the linear oxidation pathway via H4MPT linked derivatives differently. M. flagellatus “mutants defective in this (linear oxidation) pathway were more sensitive to formaldehyde than wild-type for cells grown on solid media but not in shaken liquid cultures.” The result provided clues that this pathway may serve to protect the M. flagellatus from excess formaldehyde, whereas Methylobacterium extorquens uses this pathway as its “main energy-generating pathway for methylotrophic growth.”