The mass spectral studies are further elaborated

below. Figure 1 Phototrophic growth of H. modesticaldum on pyruvate and various sugars, and mass spectra of (bacterio)chlorophylls extracted from cells grown on pyruvate and glucose. Growth of H. modesticaldum on 20 mM pyruvate, 40 mM sugars, or 0.02% yeast extract (A), and on 10 mM D-glucose, 40 mM D-glucose, or 40 mM Fostamatinib clinical trial 2′-fluoro-2′-deoxy-D-glucose (FDG) (B) as defined carbon source in the growth medium. Either no or only “”vitamin-level”" (0.02%) yeast extract is included in the growth medium, and detailed growth conditions are described in Materials and Methods. Mass spectra of (bacterio)chlorophylls extracted from cultures grown on pyruvate (I, upper panel) vs. [3-13C]pyruvate (II, lower panel) in PMS medium (C) and glucose (I, upper panel) vs. [U-13C6]glucose (II, lower panel) in YE medium (D). By optimizing the growth conditions, we successfully grew the cultures on D-ribose, D-glucose and D-fructose in the growth medium containing 0.02% yeast extract (i.e. “”vitamin level”" yeast extract), whereas no growth can be detected with only 0.02% yeast extract in the culture medium (Figure 1A). Cell growth is dependent on the concentration of D-sugars, and no growth of H. modesticaldum is seen

with 40 mM 2′-fluoro-2′-deoxy-D-glucose (FDG) as the sole carbon source (Figure 1B). Lack of the growth on check details FDG, a glucose analogue, is consistent with the mechanism of action of FDG that cannot be metabolized inside the cells because it lacks the 2′-hydroxyl group in normal glucose required for conversion of D-glucose-6-phosphate to D-fructose-6-phosphate in glycolysis. Alternatively, no growth is detected on L-arabinose, which is one of the most abundant pentoses present as a constituent of bacterial cell wall and is a more common isomer than D-arabinose.

Many bacteria contain an inducible Rebamipide operon that encodes a series of enzymes and transporters that allows L-arabinose to be used as a sole carbon source in cell culture. No arabinose transporter (araE) is annotated in the genome of H. modesticaldum. In addition to physiological studies, we also determine the uptake of D-hexose and assay the enzymatic activity for the enzymes specific for the EMP pathway. Our studies indicate 20-25% D-fructose (8-10 mM) and ~10% D-glucose (~4 mM) being assimilated, consistent with better growth on D-fructose than on D-glucose. No acetate is excreted from 40 mM glucose-grown cultures (data not shown). Enzymatic activity of hexokinase (10 nmole/min•mg protein), 6-phosphofructokinase (20 nmole/min•mg protein) and pyruvate kinase (10 nmole/min•mg protein), three enzymes specific for the EMP pathway and not shared with the gluconeogenesis pathway, can be detected in hexose-grown cultures. Together, our studies indicate that H.