Aerobic to anaerobic transition in the carbohydrate metabolism of Schistosoma mansoni cercariae during transformation in vitro

Abstract

Schistosoma mansoni cercariae in water were shown to possess a largely aerobic energy metabolism, the Krebs cycle being the main terminal of carbohydrate breakdown. A metabolic transition towards a more anaerobic breakdown of carbohydrate could be achieved by incubation conditions which also stimulated biological transformation. Incubation of cercariae in a simple salt medium containing 5 mM glucose induced such a metabolic transition: beside carbon dioxide large amounts of lactate and pyruvate were excreted. The results indicate that the production of pyruvate was coupled to electron transfer in the respiratory chain. Some aspects of this unusual pyruvate production are discussed. The observed change in the end-product pattern of carbohydrate breakdown is very rapid: most of the switch occurred within 2 h. Our results show that the metabolic transition was triggered by the biological transformation itself, or by the same event that induces the biological transformation. The metabolic and the biological changes proceeded synchronously.

Towards an understanding of the mechanism of action of praziquantel

“…These life cycle stages also have an aerobic metabolism in which endogenous glycogen is catabolized mainly to CO 2 via the Krebs cycle [44,45]. In contrast, sporocysts are not sensitive to PZQ.…”

In vitro and in silico analysis of signal peptides from the human blood fluke,Schistosoma mansoni

“…Free‐living cercariae have exploited their small size and the ready availability of oxygen in their aqueous environment to aerobically degrade endogenous energy sources and produce substantial amounts of energy in order to find and penetrate into a vertebrate host during their relatively short lifespan [23]. Furthermore, it is conceivable that cercariae may have generated the majority of their protein complement in the pre‐cercarial, sporocyst developmental stage, perhaps as a strategy to prioritise use of its finite glycogen stores in acquiring a host.…”

Fatty Acid Oxidation Is Essential for Egg Production by the Parasitic Flatworm Schistosoma mansoni

“…The fact that starvation in planaria (free living flatworms) can lead to reversible tissue involution [16] is consistent with the possibility that loss of vitelline cells is the end result of nutritional deprivation in female parasites. Glucose is considered to be the key macronutrient required by adult schistosomes to meet their bioenergetics needs [17], [18], but there is a lack of clarity in the literature regarding the relative extent to which Warburg metabolism (the homolactic fermentation of glucose in the presence of oxygen) versus mitochondrial oxidative phosphorylation (OXPHOS) are important in these organisms [17], [19], [20]. Nevertheless, fecund adult females gradually stop ovipositing in vitro even when glucose and oxygen are not limiting [21], and under anaerobic conditions egg production ceases immediately despite the fact that the worms remain viable for extended periods [17].…”