The Caenorhabditis elegans assay: a tool to evaluate the pathogenic potential of bacterial biocontrol agents

Abstract

Bacterial biocontrol agents (BCAs) open up the possibility of controlling plant pathogens in an environmentally friendly way. Although they are naturally occurring microbes, some of them can cause diseases in humans. For successful registration it is necessary to test potentially adverse effects on the human health of at-risk candidates. Existing pathogenicity assays are cost-intensive, time-consuming and furthermore they are often inappropriate for facultative pathogens. We developed a new, fast and inexpensive bioassay on the basis of the nematode Caenorhabditis elegans, which is a well-accepted model organism to study bacterial pathogenicity. A selection of eight strains from clinical and environmental origin as well as potential and commercial BCAs from the genera Bacillus, Pseudomonas, Serratia and Stenotrophomonas were screened for their potential to kill the nematode in an in vitro agar plate assay. Furthermore, the motility and reproductive behaviour of nematodes exposed to strains were tested in comparison with those fed by the human pathogen Pseudomonas aeruginosa QC14-3-8 (positive control) and the negative control Escherichia coli OP50. Commercial as well as potential biocontrol strains did not display any adverse effects in all tests. In contrast, the C. elegans assay showed slight effects for clinical and environmental Stenotrophomonas strains. Results showed that the nematode C. elegans provides a model system to indicate the pathogenic potential of BCAs in a very early stage of product development.

Quantifying Salmonella Population Dynamics in Water and Biofilms

“…All isolates as well as Salmonella enterica serovar Typhimurium LT2 (ATCC 19585) were tested for pathogenicity using feeding studies with Caenorhabditis elegans [30][31][32]. Nematodes (C. elegans strain Bristol N2) were kept as hermaphrodites on nematode growth medium (NGM) agar (in l −1 : 2.5 g peptone, 3 g NaCl, 17 g agar, 1 ml of 1 M cholesterol, 1 ml of 1 M CaCl 2 , 1 ml of 1 M MgSO 4 , 1 ml of 1 M potassium phosphate buffer, pH 6) at 20°C [33] and fed with E. coli strain OP 50.…”

Vanilla Rhizobacteria as Antagonists against Fusarium oxysporum f. sp. vanillae

“…Obtaining strains of Sphingobacterium, Psychrobacter, Pseudomonas, Serratia, Staphylococcus and Stenotrophomonas from other plant species using culture media with crab and/or shrimp shells as the only carbon source has been reported (Wolf, 2002;Chang et al, 2003;Ribbeck-Busch et al, 2005;Wang et al, 2006;Chang et al, 2009;Wang et al, 2009;Zachow et al, 2009). Likewise, strains of these genera have been reported as rhizobacteria with in vitro antagonistic activity against phytopathogenic fungi, including F. oxysporum, but not for the strain vanillae.…”

Pseudomonas Strains that Exert Biocontrol of Plant Pathogens

“…immuno-depressed patients) is compulsory. Available molecular procedures and/or novel promising approaches such as the assay with the model nematode Caenorhabditis elegans to assess the pathogenic potential of a BCA (Zachow et al 2009) are potent tools to accomplish with that aim. The same accounts for BCAs whose biocontrol activity is based on the synthesis and release of new antibiotics and/or toxic metabolites.…”