Broad-range necrophytophagy in the flagellate Orciraptor agilis (Viridiraptoridae, Cercozoa) and the underappreciated role of scavenging among protists.

Protists show diverse lifestyles and fulfill important ecological roles as primary producers, predators, symbionts, and parasites. The degradation of dead microbial biomass, instead, is mainly attributed to bacteria and fungi, while necrophagy by protists remains poorly recognized. Here, we assessed the food range specificity and feeding behavior of the algivorous flagellate Orciraptor agilis (Viridiraptoridae, Cercozoa) with a large-scale feeding experiment.

Distinct actors drive different mechanisms of biopolymer processing in polar marine coastal sediments.

Heterotrophic bacteria in the ocean initiate biopolymer degradation using extracellular enzymes that yield low molecular weight hydrolysis products in the environment, or by using a selfish uptake mechanism that retains the hydrolysate for the enzyme-producing cell. The mechanism used affects the availability of hydrolysis products to other bacteria, and thus also potentially the composition and activity of the community. In marine systems, these two mechanisms of substrate processing have been studied in the water column, but to date, have not been investigated in sediments.

Experimental evidence for enzymatic cell wall dissolution in a microbial protoplast feeder (Orciraptor agilis, Viridiraptoridae).

Background: Several protists have evolved the ability to perforate the cell walls of algae and fungi to specifically feed on their cell contents. These phagotrophic "protoplast feeders" represent an interesting mechanistic intermediate between predators and parasites and pose a number of cell biological questions. Although their fascinating feeding behaviour has been observed for the last 150 years, it is still unknown how protoplast feeders produce the well-defined and species-specific perforations in biochemically diverse cell walls.