Multiple integrated metabolic strategies allow foraminiferan protists to thrive in anoxic marine sediments

Oceanic deoxygenation is increasingly affecting marine ecosystems; many taxa will be severely challenged, yet certain nominally aerobic foraminifera (rhizarian protists) thrive in oxygen-depleted to anoxic, sometimes sulfidic, sediments uninhabitable to most eukaryotes. Gene expression analyses of foraminifera common to severely hypoxic or anoxic sediments identified metabolic strategies used by this abundant taxon. In field-collected and laboratory-incubated samples, foraminifera expressed denitrification genes regardless of oxygen regime with a putative nitric oxide dismutase, a characteristic enzyme of oxygenic denitrification. A pyruvate:ferredoxin oxidoreductase was highly expressed, indicating the capability for anaerobic energy generation during exposure to hypoxia and anoxia. Near-complete expression of a diatom’s plastid genome in one foraminiferal species suggests kleptoplasty or sequestration of functional plastids, conferring a metabolic advantage despite the host living far below the euphotic zone. Through a unique integration of functions largely unrecognized among “typical” eukaryotes, benthic foraminifera represent winning microeukaryotes in the face of ongoing oceanic deoxygenation.

Endocytosis and the internalization of pathogenic organisms: focus on phosphoinositides

Despite their comparatively low abundance in biological membranes, phosphoinositides are key to the regulation of a diverse array of signaling pathways and direct membrane traffic. The role of phosphoinositides in the initiation and progression of endocytic pathways has been studied in considerable depth. Recent advances have revealed that distinct phosphoinositide species feature prominently in clathrin-dependent and -independent endocytosis as well as in phagocytosis and macropinocytosis. Moreover, a variety of intracellular and cell-associated pathogens have developed strategies to commandeer host cell phosphoinositide metabolism to gain entry and/or metabolic advantage, thereby promoting their survival and proliferation. Here, we briefly survey the current knowledge on the involvement of phosphoinositides in endocytosis, phagocytosis, and macropinocytosis and highlight several examples of molecular mimicry employed by pathogens to either “hitch a ride” on endocytic pathways endogenous to the host or create an entry path of their own.

Respiratory faculties of amphibious and terrestrial invertebrates

This chapter focuses on the respiratory faculties of invertebrate air breathers. Although the partial pressure of oxygen in water is the same as in the surrounding atmosphere, the oxygen content per unit volume is around 30 times less due to its relatively low solubility in water. So it is no wonder that there is evidence for invertebrate animals on land as early as from the Palaeozoic. In spite of this apparent metabolic advantage, aside from some annelid groups, the only invertebrates to truly call dry land their home are some snails and arthropods. Among the latter, we see several independent origins of air breathing, and crustaceans present a particularly interesting study group in this regard. Arachnids and insects, on the other hand, were from the beginning terrestrial and air breathing, and insect tracheae form the most effective respiratory system going.

Carbs versus fat: does it really matter for maintaining lost weight?

The most read article of 2018 published in The BMJ (https://doi.org/10.1136/bmj.k4583) claimed that restricting dietary carbohydrates offers a metabolic advantage to burn more calories and thereby help patients maintain lost weight. However, analyzing the data according to the original pre-registered statistical plan resulted in no statistically significant effects of diet composition on energy expenditure. The large reported diet effects on energy expenditure calculated using the revised analysis plan depended on data from subjects with excessive amounts of unaccounted energy. Adjusting the data to be commensurate with energy conservation resulted in a diet effect that was less than half the value reported in The BMJ paper. Furthermore, the measured daily average CO2 production rates were not significantly different between the diets and the reported expenditure differences were due to inaccurate calculations based on false assumptions about diet adherence.

A high-fat diet is deleterious to mice under glycolysis restriction

It is debated whether carbohydrate restriction has metabolic advantage for its variable weight loss. Five-week-old male mice fed a high-fat diet and receiving a glycolytic inhibitor, 2-deoxyglucose, died within 9 days. They exhibited greater decreases in rectal temperature, appetite, and decline in body weight accompanied by increasing total cholesterol level than the other groups. This study suggests that carbohydrate is necessary for adequate physical and metabolic performance when lipid-rich diet is loaded.