Characterization of the putative antigenic determinants on Pasteuria endospore surface using Bacillus thuringiensis as a comparative tool

Abstract

Biological control agents are emerging as potential environmentally benign means of combating phytonematodes across the world. Some species of Pasteuria are endospore forming bacterial hyperparasites of nematodes associated with nematode suppressive soils. The prospective use of these bacteria in nematode management is well acknowledged by the scientific community. However, the mechanism by which Pasteuria endospores attach to the nematode cuticle and infect their nematode hosts is yet to be understood. Previously the involvement of parasporal collagen-like fibres present on the exosporium of Pasteuria endospores have been suggested as specificity determinants. Collagen-like fibres similar to Pasteuria parasporal fibres are known to exist and are well characterized on the exosporium of other closely related animal pathogenic Bacillus spp. Using comparative studies we explore the surface architecture and antigenic properties of Pasteuria endospores. Protein extracts from endospores of Bacillus thuringiensis and Pasteuria were compared using Western blot analysis. Antibodies raised against whole Pasteuria endospores and to synthetic peptides of Pasteuria collagen-like proteins showed cross-reactivity to endospore extracts B. thuringiensis. Further antigenic similarities in their exosporium have been confirmed by immunofluorescence microscopic studies where endospores from both the genera were labelled equally with Pasteuria ¬–specific antibodies. To further understand the determinants involved in the Pasteuria-nematode attachment process, Pasteuria endospores were treated with collagenase, β-N acetylglucosaminidase and anti-collagen antibodies and in vitro attachment assays were performed. We observed a marked decrease in the number of endospores attached to the nematode juveniles