Application of ALFA-Tagging in the Nematode Model Organisms Caenorhabditis elegans and Pristionchus pacificus.

The detection, manipulation and purification of proteins is key in modern life sciences studies. To achieve this goal, a plethora of epitope tags have been employed in model organisms from bacteria to humans. Recently, the introduction of the rationally designed ALFA-tag resulted in a highly versatile tool with a very broad spectrum of potential applications. ALFA-tagged proteins can be detected by nanobodies, the single-domain antibodies of camelids, allowing for super-resolution microscopy and immunoprecipitation in biochemical applications. Here, we introduce ALFA-tagging into the two nematode model organisms Caenorhabditis elegans and Pristionchus pacificus. We show that the introduction of the DNA sequence, corresponding to the 13 amino acid sequence of the ALFA-tag, can easily be accommodated by CRISPR engineering. We provide examples of high-resolution protein expression in both nematodes. Finally, we use the GW182 ortholog Ppa-ain-1 to show successful pulldowns in P. pacificus. Thus, the ALFA-tag represents a novel epitope tag for nematode research with a broad spectrum of applications.

Effects of Mercury (Hg) on Soil Nematodes: A Microcosm Approach.

Mercury (Hg), one of the most toxic heavy metals, is commonly used in the gold extraction process in small-scale mining operations in many countries. Our previous field work on the impact of mining on soil nematode assemblages in a small-scale mining area in Sibutad, the Philippines, revealed no significant negative effects despite sometimes strongly elevated Hg concentrations. Using a microcosm approach, we now applied similar Hg concentrations as commonly found in these field sites (2.5, 5, and 10 mg/kg Hg) and determined their impact on nematode assemblages from a different soil with different physicochemical soil attributes. Our results demonstrate (a) limited "bottling" effects (incubation effects) after a 45-day incubation period: a nematode abundance decrease of up to 37%, but absence of significant differences in diversity and nematode assemblage composition; (b) that total nematode abundance already decreased at Hg concentrations (2.5 mg/kg), which did not yield significant impacts on other nematode assemblage descriptors, such as assemblage composition and different diversity indices; and (c) that the Hg concentrations found in the Sibutad field sites can be detrimental to soil nematode assemblages. The discrepancy between our microcosm and the field-based results is probably related to differences in physicochemical soil attributes (e.g., OM contents, soil pH), which suggests that nematode-based environmental assessments should be interpreted in a context-dependent manner.