Abstract
ABSTRACTSoil microbes are a major food source for free-living soil nematodes. It is known that certain soil bacteria have evolved systems to combat predation. We identified the nematode-antagonistic Pseudomonas protegens strain 15G2 from screening of microbes. Through protein purification we identified a binary protein, designated Pp-ANP, which is responsible for the nematicidal activity. This binary protein inhibits Caenorhabditis elegans growth and development by arresting larvae at the L1 stage and killing older-staged worms. The two subunits, Pp-ANP1a and Pp-ANP2a, are active when reconstituted from separate expression in Escherichia coli. The binary toxin also shows strong nematicidal activity against three other free-living nematodes (Pristionchus pacificus, Panagrellus redivivus, and Acrobeloides sp.), but we did not find any activity against insects and fungi under test conditions, indicating specificity for nematodes. Pp-ANP1a has no significant identity to any known proteins, while Pp-ANP2a shows ∼30% identity to E. coli heat-labile enterotoxin (LT) subunit A and cholera toxin (CT) subunit A. Protein modeling indicates that Pp-ANP2a is structurally similar to CT/LT and likely acts as an ADP-ribosyltransferase. Despite the similarity, Pp-ANP shows several characteristics distinct from CT/LT toxins. Our results indicate that Pp-ANP is a new enterotoxin-like binary toxin with potent and specific activity to nematodes. The potency and specificity of Pp-ANP suggest applications in controlling parasitic nematodes and open an avenue for further research on its mechanism of action and role in bacterium-nematode interaction.IMPORTANCE This study reports the discovery of a new enterotoxin-like binary protein, Pp-ANP, from a Pseudomonas protegens strain. Pp-ANP shows strong nematicidal activity against Caenorhabditis elegans larvae and older-staged worms. It also shows strong activity on other free-living nematodes (Pristionchus pacificus, Panagrellus redivivus, and Acrobeloides sp.). The two subunits, Pp-ANP1a and Pp-ANP2a, can be expressed separately and reconstituted to form the active complex. Pp-ANP shows some distinct characteristics compared with other toxins, including Escherichia coli enterotoxin and cholera toxin. The present study indicates that Pp-ANP is a novel binary toxin and that it has potential applications in controlling parasitic nematodes and in studying toxin-host interaction.
Highlights
Soil microbes are a major food source for free-living soil nematodes
Overnight cultures of individual bacterial strains were tested against C. elegans in a liquid assay
Root-colonizing bacterium P. fluorescens CHA0, which was isolated from a suppressive soil, has been studied in detail as a strain for the biological control of root-knot nematodes [19, 20]
Summary
Soil microbes are a major food source for free-living soil nematodes. It is known that certain soil bacteria have evolved systems to combat predation. Some pathogenic bacteria are capable of proliferating in and killing nematodes by an infectious process or through the use of toxins [1,2,3,4] Some rhizosphere bacteria, such as Pseudomonas and Serratia, showed antagonistic effects on plant parasitic nematodes by proteinases and second-. Pseudomonas protegens 15G2, we identified a novel binary toxin, designated Pp-ANP, which showed strong nematicidal activity against multiple nematode species. This toxin holds promise for controlling parasitic nematodes and is useful for studying toxin-host and bacteriumnematode interactions
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have