After cultivation of cells on minimal salts medium with gluconate, or glucose in the case of Rhodococcus TGF beta inhibitor ruber and Rhodococcus

equi, because gluconate supported poor growth of cells, as the sole carbon source, a phenol–sulfuric acid-reactive material was detected in all bacteria investigated as revealed by TLC analysis. A commercial glycogen was used as a standard for TLC analysis (data not shown). Enzymatic analysis of the isolated polysaccharide after 24 h of growth indicated that in all cases, the material observed was a glucose polymer. In general, the glycogen content amounted to approximately up to 5% of CDW in the strains studied as shown in Table 3. Among these microorganisms, R. equi produced higher amounts of glycogen than other bacteria, whereas R. opacus PD630 and R. ruber produced only scant amounts of glycogen under the culture conditions used in this study (Table 3). In all cases, no significant differences were observed (data not shown) between glycogen contents of the respective strains cultivated in a nitrogen-poor mineral medium and in a nitrogen-rich medium (NB medium). The results of the analyses of glycogen accumulation as well as those obtained in the survey of key genes for glycogen metabolism suggested that find more the ability to produce glycogen may be a common feature among Rhodococcus strains.

Rhodococcus opacus PD630 is a triacylglycerol -accumulating specialist that has become a model among prokaryotes in the lipid research area. The triacylglycerol content and composition of strain PD630 cultivated on a diversity of substrates has been reported previously (Alvarez et al., 1996, 1997). Because the content and composition of accumulated triacylglycerols depend on the Nutlin-3 datasheet carbon source used for cell cultivation (Alvarez et al., 1996, 1997), we investigated the influence of carbon sources on the glycogen accumulation in this oleaginous bacterium. Figure 1 shows the glycogen content of cells cultivated on different substrates, during the exponential and stationary growth phases. The glycogen content in the

cells amounted to between 0.8±0.3 (sucrose, fructose and gluconate) and 3.2±0.2% CDW (maltose) after cultivation under nitrogen-limiting conditions. Maltose and pyruvate promoted glycogen accumulation to a level approximately threefold greater in comparison with the other substrates used, such as glucose, sucrose, acetate and lactose (Fig. 1). Interestingly, cells grown on maltose (34.1% CDW of triacylglycerols) and pyruvate (39.2% CDW of triacylglycerols) accumulated lower amounts of triacylglycerols in comparison with cells cultivated with gluconate (60.0% CDW of triacylglycerols), suggesting an inverse relationship between the triacylglycerols and glycogen contents in cells. The results indicated that the amount of glycogen accumulated by strain PD630 depends on the carbon source used for the cultivation of cells.