Cell dry weight (cdw) was determined using a filtration method as described

previously (Willquist & van Niel, 2010). Protein levels were determined according to Bradford (1976) using bovine serum albumin as the standard. Nucleotide sequences of the investigated genes were retrieved either from the IMG database (http://img.jgi.doe.gov/cgi-bin/pub/main.cgi) or from BMN 673 concentration GenBank (http://www.ncbi.nlm.nih.gov/). Sequence alignments were performed using clustal x (V1.83) (Jeanmougin et al., 1998). Molecular phylogenetic analysis was performed using the distance (neighborhood-joining) method. Gene-neighborhood analysis was performed using the ortholog neighborhood viewer available at the IMG site. Cells (OD660 nm 0.3–0.4) were harvested (50 mL) during the mid-logarithmic growth phase by centrifugation (10 min, 4570 g). Cell pellets were suspended in Tris-HCl buffer (100 mM, pH 7.2) containing MgCl2 (5 mM) and NaCl (40 mM)) (Willquist & van Niel, 2010). Cells were disrupted by sonification NVP-AUY922 solubility dmso and CEs were prepared by centrifugation (10 min, 16 000 g). Membrane and cytosolic fractions were obtained by additional centrifugation (1 h, 100 000 g) of the CE, where the membranes were resuspended in the indicated buffer. Extracts were stored

at −20 °C until further use. The determination of enzyme activities was carried out with two biological and four technical replicates. Enzyme activities of PPDK (EC 2.7.9.1), PK (EC 2.7.1.40), ATP- and PPi-dependent (PFK) (ATP-PFK, EC 2.7.1.11, PPi-PFK, EC 2.7.1.90) were determined in the described Tris buffer, which was additionally reduced with dithiothreitol (5 mM). Assays were performed at 50 °C, to ensure auxiliary enzyme activity. All Proteases inhibitor auxiliary enzymes were purchased from Sigma Aldrich. Substrate conversions were coupled to the oxidation of NADH (ɛ334=6.18 mM−1 cm−1). The PPDK and PK assays were coupled to the conversion of pyruvate to lactate using l-LDH as an auxiliary enzyme. To determine the influence of the PPi concentration on PK activity, low-molecular-weight

compounds were first removed from CEs (MW below 5 kDa) using a PD10 desalting column (GE Healthcare, Willquist & van Niel, 2010). These later assays were performed at 70 °C using a thermostable LDH as an auxiliary enzyme. The PFK activity was assayed by coupling to the reduction of dihydroxyacetone phosphate (DHAP) to glycerol-3-phosphate, catalyzed by glycerol-3-phosphate dehydrogenase (GPDH), using fructose 1,6-bisphosphate aldolase (FBA) and triose-phosphate isomerase (TPI) as auxiliary enzymes. One unit of enzyme activity is defined as that amount of the enzyme that catalyzes the conversion of 1 μmol of substrate min−1. The reaction mixtures for PPDK contained: LDH (6.8 U, from chicken heart), NADH (0.25 mM), NH4Cl (25 mM), PEP (2 mM), AMP (2 mM) and PPi (0.4 mM); for PK: LDH (6.8 U), NADH (0.25 mM), PEP (2 mM) and ADP (2 mM); for PPi-PFK: GPDH (1.3 U, from rabbit muscle), FBA (0.