Processes of programmed cell death have been reported and monitored in vegetative mycelium of Streptomyces sp. [23,24]. The portion of metabolic active cells in the total cell mass INK1197 nmr therefore decreases as pellet size increases during

the lifetime of a batch culture, implying a significant influence on and a possible overestimation of observed decreasing trends in the heat maps since the metabolite pools are normalized to total cell mass. In addition, a positive correlation between specific growth rate and intracellular Inhibitors,research,lifescience,medical nucleotide phosphate pool concentrations or specific productivities bacterial species is well established for different bacterial species [25,26]. As a consequence, the observation that the nucleotide pools in the present study of S. coelicolor are highest in early growth phase is therefore not unexpected since in this metabolically most active phase, the specific growth rate is highest and the portion of dead mycelium is relatively low. Later in middle and late growth phase, Inhibitors,research,lifescience,medical the specific growth rate/specific oxygen consumption rate gradually declines [27], giving rise to the observed decrease in the total nucleotide phosphate pool. Similar profiles of decreasing nucleotide phosphate pools likely also demonstrating this combined effect of Inhibitors,research,lifescience,medical increasing portions of metabolically inactive cell mass and

decreasing specific growth rates have previously been reported, e.g., for different Streptomyces spp. [28,29,30]. Figure Inhibitors,research,lifescience,medical 2 Time-course heat map representations of the 20 most abundant metabolites analyzed by the MCF GC-MS method (left hand side) and the 25 most abundant metabolites analyzed by the LC-MS/MS method (right hand side) detected in time-course samples of cultivations … Despite the decreasing nucleotide pool, Inhibitors,research,lifescience,medical the energy charge (EC) in S. fradiae was found to be constant [29], pointing to a significant influence of the mycelial live/dead ratio on the measured concentrations of the total nucleotide pools

while the ratio of ATP, ADP and AMP concentrations was maintained. Also in our study, the EC already values were found to be relatively constant around 0.5–0.6 (Supplementary Figure 1). It is of general concern in metabolite analysis that determined EC values can be due to biases introduced during sample processing. Nevertheless, there are reports that the use of EC as a metabolic integrity characteristic is not unambiguous, and there are also reports that modify the general perception of the EC. Van der Werf and co-workers for example [31] reported EC values below 0.1 for glucose grown Pseudomonas putida cells while fructose grown cells showed an EC above 0.8. Barrette and co-workers [32] measured EC values below 0.2 during nutrient limitation but showed that cells easily recovered when exposed to more nutrient rich conditions.