Purine Auxotrophic Starvation Evokes Phenotype Similar to Stationary Phase Cells in Budding Yeast

Purine auxotrophy is an abundant trait among eukaryotic parasites and a typical marker for many budding yeast strains. Supplementation with an additional purine source (such as adenine) is necessary to cultivate these strains. If not supplied in adequate amounts, purine starvation sets in. We explored purine starvation effects in a model organism, a budding yeast Saccharomyces cerevisiae ade8 knockout, at the level of cellular morphology, central carbon metabolism, and global transcriptome. We observed that purine-starved cells stopped their cycle in G1/G0 state and accumulated trehalose, and the intracellular concentration of AXP decreased, but adenylate charge remained stable. Cells became tolerant to severe environmental stresses. Intracellular RNA concentration decreased, and massive downregulation of ribosomal biosynthesis genes occurred. We proved that the expression of new proteins during purine starvation is critical for cells to attain stress tolerance phenotype Msn2/4p targets are upregulated in purine-starved cells when compared to cells cultivated in purine-rich media. The overall transcriptomic response to purine starvation resembles that of stationary phase cells. Our results demonstrate that the induction of a strong stress resistance phenotype in budding yeast can be caused not only by natural starvation, but also starvation for metabolic intermediates, such as purines.

Purine auxotrophic starvation evokes quiescence like phenotype in the budding yeast

Purine auxotrophy is a typical marker for many laboratory yeast strains. Supplementation of additional purine source (like adenine) is necessary to cultivate these strains. If not supplied in adequate amounts, purine starvation sets in. We tested purine starvation effects in budding yeast Saccharomyces cerevisiae ade8 knockout. We explored effects brought by purine starvation in cellular, central carbon metabolism and in the global transcriptome level. We observed that cells cultivated in purine depleted media became significantly more tolerant to severe thermal, oxidative and desiccation stresses when compared to the cells cultivated in media with all necessary supplements. When starved for purine, cells stop their cell cycle in G1 or G0 state; intracellular concentration of ATP, ADP and AMP decreases, but adenylate charge remains stable. Intracellular RNA concentration decreases and massive downregulation of ribosomal RNA occurs. We think that purine auxotrophic starvation in a way mimics natural nitrogen or carbon starvations and therefore initiates elements of a transcriptional program typical for stationary phase cells (cell cycle arrest, increased stress resistance). Therefore our results demonstrate that organised metabolic response is initiated not only via natural starvations, but also when starving for metabolic intermediates, like purines.

Decentralized Routing Algorithm with Physical Time Windows for Modular Conveyors

We describe a decentralized routing algorithm with physical time windows for modular conveying systems. Existing routing algorithms for modular conveyors are already capable of bi-directional conveying while avoiding conflicts such as collisions, deadlocks, livelocks and starvation effects. In addition to avoiding conflicts, routing algorithms must also select routes that reduce the travel time. No existing algorithm for modular conveyors bases this decision on the expected physical lead time, even though physical lead time directly affects the system throughput. In this publication, we present an algorithm that uses the physical lead time to select routes while avoiding conflicts.

Starvation effects on nitrogen and carbon stable isotopes of animals: an insight from meta-analysis of fasting experiments

Nitrogen and carbon stable isotopic compositions ( δ 15 N and δ 13 C) of consumers have been used for physiological and food web studies. Previous studies have shown δ 15 N and δ 13 C values are affected by several biological and environmental factors during starvation, but the generality of the effect of starvation on δ 15 N and δ 13 C values has not yet been tested. Here, we performed a meta-analysis to evaluate the effects of starvation on δ 15 N and δ 13 C values of consumers, and the underlying factors that may explain the observed variation. The δ 15 N and δ 13 C values were calculated as the differences between the final δ 15 N and δ 13 C values of consumers (post-starvation) and the pre-starvation values on each experiment. Our meta-analysis showed a large variation in the δ 15 N and δ 13 C values of consumers (δ 15 N range: –0.82 to 4.30‰; mean: 0.47‰ and δ 13 C range: –1.92 to 2.62‰; mean: 0.01‰). The δ 15 N values of most consumers increased along the length of the starvation period and were influenced by nitrogen excretion and thermoregulation types, probably because differences in nitrogen metabolism and thermoregulation affect nitrogen processing and excretion rates. None of our predictor variables accounted for the variation in δ 13 C values, which showed both increases and decreases due to fasting. Our findings suggest that starvation results in changes in consumer δ 15 N values which are mainly explained by the length of the fasting period and by nitrogen and energy metabolism, but the underlying mechanisms of the starvation effects on δ 13 C values seem to be more complex than previously thought.

Prolonged starvation effects on ascorbic acid level in the muscles of a freshwater teleost, Clarias batrachus

The effect of prolonged food deprivation on ascorbic acid content of muscles has been observed in both the sexes of the fish. The level of ascorbic acid content was found relatively higher in males than in females. In males, the muscles showed higher value of ascorbic acid in normal condition (12.07mg/100gm) in comparison to that of females (9.66mg/100gm). During starvation, the gradual decrease in ascorbic acid level has been noticed in both the sexes of the fish. After 40 days of starvation, the higher depletion was observed in female (about 84%) and lower depletion in the male (about 81%) of C. batrachus. This shows substantial decline in aerobic and biosynthetic capacity of the fish during starvation period.