Physiological states and energetic adaptation during growth of Pseudomonas putida mt-2 on glucose
Abstract
Kinetic study of growth of Pseudomonas putida mt-2 was investigated in batch culture under aerobic conditions, on glucose as initial carbon and energy source. Cell growth was continuous and three phases were found regarding accumulation of intermediates: (1) glucose was largely converted to gluconate and 2-ketogluconate, (2) then gluconate was converted to 2-ketogluconate and (3) the latter was consumed after gluconate depletion. Examination of growth kinetics and yields showed that glucose flux was mainly oriented to oxidation reduction in the periplasm and less towards biosynthesis. Values of respiratory quotient and of CO2/biomass and O2/biomass yields were characteristic of each phase. Main enzymatic activities involved in the use of these substrates were always detected meaning that concomitant assimilation is possible. However the levels of these activities varied during growth. Membrane conversions seem to have a significant energetic contribution explaining the higher specific growth rate obtained in glucose phase compared to gluconate and 2-ketogluconate ones. This is also noticeable through the evolution of the yields Y(O2)/X and Y(CO2)/X. Although the three convergent pathways are operational and can be genetically controlled, the progression of the culture in successive phases highlights an overall level of regulation in response to the energetic needs.