nucleatum to generate energy and produce ammonia, acetate and butanoate as end-products [45–47]. The bacterium also ferments sugars (glucose, galactose and fructose) to produce a mixture of acetate, formate and lactate [48]. Figure 2 Representation of protein groups that were regulated at pH 8.2 compared to 7.4. In the present study, key enzymes involved in IWP-2 chemical structure the catabolism of glutamate and histidine via the 2-oxoglutarate pathway and pyruvate were significantly SAR302503 altered in biofilm cells (Table 1). A previous study of F. nucleatum

cultured at pH 6.4, 7.4 and 7.8 also revealed the regulation of metabolic enzymes [26]. In contrast to this finding, we found that no glycolytic enzyme concentrations were altered in biofilm cells grown at pH 8.2 compared to planktonic cells grown at 7.4. However, a three-fold increase in glucose utilisation and IP was observed (Table 2, Figure 3).

It is possible that the observed increase in glucose storage may play an important role in the organism’s survival during periods of nutrient limitation when exposed to pH 8.2 [43, 49, 50]. Although the expression of glycolytic enzymes was not significantly altered, an increase in lactate dehydrogenase (LDH) (EC 1.1.2.8) and a three-fold increase in lactate production was observed, indicating a metabolic Selleckchem STA-9090 shift at pH 8.2 towards ATP generation via anaerobic glycolysis (Embden-Meyerhof-Parnas pathway) (Tables 1 and 2, Figure 3). In addition, at pH 8.2, an increase in acidic click here end products per mg cellular protein and shift to lactate

production was observed (Table 2). These changes may assist in maintenance of intracellular pH due to the lower pKa of lactic acid (3.08) compared to formic (3.75), acetic (4.75) and butanoic (4.82) acids. . Table 2 Glucose consumption and metabolic end-products produced by F. nucleatum grown at pH 8.2 and 7.4 Growth pH Glucose utilisation1 IP2 Acidic end-products3 GDH4       Lactate Formate Acetate Butanoate   7.4 ± 0.1 23.1 ± 2.1 2.39 ± 0.12 5.7 ± 0.5 92.4 ± 8.6 59.4 ± 6.5 63.0 ± 5.1 8.87 ± 0.40 8.2 ± 0.1 65.9 ± 7.2 7.62 ± 0.71 18.3 ± 1.9 131.2 ± 11.6 115.3 ± 12.7 99.6 ± 10.8 13.73 ± 1.25 1Glucose utilisation expressed as mmoles of glucose g-1 cell protein. 2Intracellular polyglucose expressed as μg glucose mg-1 cell protein. 3Acidic end-products expressed in mmol g-1 cell protein. 4NAD-specific glutamate dehydrogenase (GDH) activity measured in cells expressed as GDH unit mg-1 cell protein Figure 3 Pathways for glucose and histidine/glutamate catabolism in F. nucleatum. Significantly regulated enzymes detected in this study at pH 8.2 are indicated by the enzyme commission (E.C) numbers (Refer to Table 1). Bold arrows indicate increased enzyme levels while double-slash indicates decreased enzyme expression.