Pathogen–nematode interaction: Nitrogen supply ofListeria monocytogenesduring growth inCaenorhabditis elegans

Abstract

Listeria monocytogenes is a Gram-positive facultatively intracellular human pathogen. Due to its saprophytic lifestyle, L. monocytogenes is assumed to infect and proliferate within soil organisms such as Caenorhabditis elegans. However, little is known about the nutrient usages and metabolite fluxes in this bacterium-nematode interaction. Here, we established a nematode colonization model for L. monocytogenes and a method for the efficient separation of the pathogen from the nematodal gut. Following (15)N labelling of C. elegans and gas chromatography-mass spectrometry-based (15)N isotopologue analysis, we detected a high basal metabolic rate of the nematode, and observed a significant metabolic flux from nitrogenous compounds of the nematode to listerial proteins during proliferation of the pathogen in the worm's intestine. For comparison, we also measured the N fluxes from the gut content into listerial proteins using completely (15)N-labelled Escherichia coli OP50 as food for C. elegans. In both settings, L. monocytogenes prefers the direct incorporation of histidine, arginine and lysine over their de novo biosynthesis. Our data suggest that colonization of nematodes is a strategy of L. monocytogenes to increase its access to N-rich nutrients.

Isotopologue profiling of the listerial N‐metabolism

“…To summarize, L. monocytogenes is able to use multiple N-sources during growth in a defined MM and exhibits a high flexibility with respect to the simultaneous exploitation of alternative N-sources such as ethanolamine and GlcN. The relevance of the utilization of the latter substrates as N-sources by L. monocytogenes during infection, however, remains to be addressed (Buchrieser et al, 2003;Kern et al, 2015). Interestingly, the genes involved in ethanolamine utilization are upregulated during growth of L. monocytogenes in the intestinal tract of mice (Toledo-Arana et al, 2009) and contribute to replication in Caco-2 cells (Joseph et al, 2006).…”

“…A key technology to answer these questions is isotopologue profiling that has been applied to study the carbon metabolism of L. monocytogenes under various conditions by introducing diverse 13 C-labeled tracers (Eisenreich et al, 2006;Eylert et al, 2008;Joseph et al, 2008;Eisenreich et al, 2010;Grubm€ uller et al, 2014). Recently, we used 15 N-isotopologue profiling to demonstrate N-fluxes from Caenorhabditis elegans to L. monocytogenes during infection (Kern et al, 2015).…”

Multiple Substrate Usage of Coxiella burnetii to Feed a Bipartite Metabolic Network

“…In recent years, isotopolog profiling has proven to be a powerful approach to describe substrate and pathway usages for a number of pathogens including L. pneumophila (Eylert et al, 2010; Schunder et al, 2014; Häuslein et al, 2015; Gillmaier et al, 2016; Kern et al, 2016). The method is based on 13 C-incorporation experiments using completely or selectively 13 C-labeled substrates such as glucose, serine or glycerol.…”

The nematode worm Caenorhabditis elegans as an animal experiment replacement for assessing the virulence of different Salmonella enterica strains

“…This auxotrophy reduced the virulence by a factor of ten. However, attenuation based on the histidine and adenine auxotrophy in the Salmonella vaccine strain might be compensated in the worm's intestine through direct uptake of amino acids from the gut, as shown in Kern et al ( 2016 ) for Listeria. Nevertheless, the results showed that the combined attenuation of the Salmonella vaccine strain was sufficient to restore the lifespan of C. elegans to those of worms fed with E. coli OP50.…”