Use of mass spectrometry for characterizing the growth of Pseudomonas bacteria bearing naphthalene degradation plasmids

Major metabolites formed by Pseudomonas bacteria bearing various naphthalene degradation plasmids were identified using high performance liquid chromatography and mass spectrometry in combination with electrospray ionization. During the growth of P. aureofaciens BS1393(NPL-41) bacteria bearing the plasmid NPL-41, partial oxidation of naphthalene was shown to occur to form the major exometabolite (salicylate) and minor exometabolite (phenol). The growth of P. aureofaciens BS1393(pOV17) bacteria bearing the plasmid pOV17 was accompanied by complete oxidation of naphthalene and formation of trace amounts of salicylate and epoxybenzene. Based on the data of molecular mass spectrometry, we determined the dynamics of CO2 production and oxygen uptake in the process of bacterial growth. The specific quantity of CO2 per unit of cell amount for P. aureofaciens BS1393(NPL-41) bacteria was shown to exceed fivefold that for P. aureofaciens BS1393(pOV17). The respiratory quotient (RQ) representing the ratio of the molar concentrations of metabolic CO2 to consumed oxygen depends on the type of plasmids that determine naphthalene degradation. The value of RQ during the growth of P. aureofaciens BS1393(pOV17) bacteria was almost 1.5 times greater than in the case of P. aureofaciens BS1393(NPL-41). The ratio of O2 uptake to CO2 formed by the first culture was 4.5 mol O2/mol CO2; by the second culture, 6.5 mol O2/mol CO2.