EFFECT OF PYROPHOSPHATE ON GROWTH AND METABOLISM OF METHYLOMONAS-METHANICA

The obligate methanotroph Methylomonas methanica was shown to be capab le of using exogenous pyrophosphate (PPi) as a phosphorus and energy s ource. The maximum values of the specific growth rate (mu(max)) of the culture in a pH-auxostat regime on media with pyrophosphate, orthopho sphate, or their mixture (1:1 with respect to P-i) were 0.209, 0.353, and 0.329 h(-1), respectively. In cells grown in the presence of pyrop hosphate, the orthophosphate and ATP concentrations decreased but the levels of PPi, inorganic pyrophosphatase, and alkaline phosphatase inc reased. The activity of the PPi-dependent phosphofructokinase changed insignificantly. A relatively low growth rate of the culture in the pr esence of PPi may be due to the limitation of its growth by orthophosp hate. The possible role of pyrophosphate in primary metabolism of M. m ethanica is discussed. A new stoichiometric equation of the ribulose m onophosphate cycle is suggested: 3CH(2)O + PPi --> triose phosphate P-i.