Glycogen formation by Rhodococcus species and the effect of inhibition of lipid biosynthesis on glycogen accumulation in Rhodococcus opacus PD630

Abstract

Members of the genus Rhodococcus were investigated for their ability to produce glycogen during cultivation on gluconate or glucose. Strains belonging to Rhodococcus ruber, Rhodococcus opacus, Rhodococcus fascians, Rhodococcus erythropolis and Rhodococcus equi were able to produce glycogen up to 0.2–5.6% of cellular dry weight (CDW). The glycogen content varied from 0.8% to 3.2% of CDW in cells of R. opacus PD630, which is a well-known oleaginous bacterium, during the exponential growth phase, when cultivated on diverse carbon sources. Maltose and pyruvate promoted glycogen accumulation by cells of strain PD630 to a greater extent than glucose, gluconate, lactose, sucrose or acetate. This strain was able to produce triacylglycerols, polyhydroxyalkanoates and glycogen as storage compounds during growth on gluconate, although triacylglycerols were always the main product under the conditions of this study. Cerulenin, an inhibitor of de novo fatty acid synthesis, inhibited the accumulation of triacylglycerols from gluconate and increased the content of polyhydroxyalkanoates (from 2.0% to 4.2%, CDW) and glycogen (from 0.1% to 3.0%, CDW). An increase of the polyhydroxyalkanoates and glycogen content was also observed in two mutants of R. opacus PD630, which produced reduced amounts of triacylglycerols during cultivation of cells on gluconate.

Glucosamine-6P and glucosamine-1P, respectively an activator and a substrate of rhodococcal ADP-glucose pyrophosphorylases, show a hint to ascertain (actino)bacterial glucosamine metabolism

“…The latter supports a link between glycogen and amino sugars metabolism, where an increase in GlcN-6P (either by exogenous intake of GlcN or by peptidoglycan degradation [13]) might trigger the temporary accumulation of carbon in the glycogen form. This scenario agrees with the metabolic role proposed for the polyglucan in this oleaginous bacterium [2,3]. Besides, we established that GlcN-6P also activates the Rjo ADP-GlcPPase catalysis for the use of GlcN-1P (Figure 2B), sustaining the idea of an effector/substrate relationship similar to the canonical Glc-6P/Glc-1P.…”

“…The buildup of triacylglycerols is a common feature among actinobacteria belonging to the Rhodococcus genus. For example, R. jostii RHA1, produces high amounts (up to 60%) of lipids under nutrient starvation, thus being an oleaginous bacterium [1–3]. The latter represents a relevant biotechnological tool and positions rhodococci as critical for bioconversion processes to obtain biofuels precursors from simple carbon sources [1,4].…”

Regulatory Properties of the ADP-Glucose Pyrophosphorylase from the Clostridial Firmicutes Member Ruminococcus albus

“…Extraction and quantification of polysaccharides. An alkali treatment protocol was conducted for polysaccharide extraction, as described previously (12,(39)(40)(41). Samples of 10 ml from E. coli AC70RI-504 cells transformed with pMAB5/RalglgC, pMAB6/RalglgD, or both plasmids together were pelleted, washed with ice-cold water, resuspended to an OD 600 of 5.0, and boiled for 5 min.…”

Insights into the Metabolism of Oleaginous Rhodococcus spp

“…Oleaginous rhodococci produce glycogen at small amounts (between 0.3% and 5% of their weight [dry weight]) mostly during the exponential growth phase, independently of the carbon source used (30,31). In R. jostii RHA1, glycogen biosynthesis is allosterically regulated through the activity of the ADP-glucose pyrophosphorylase (ADP-Glc PPase) enzyme (32).…”