Genetic and Immunological Comparison of the Cladoceran Parasite Pasteuria ramosa with the Nematode Parasite Pasteuria penetrans

Abstract

Pasteuria penetrans, an obligate endospore-forming parasite of Meloidogyne spp. (root knot nematodes), has been identified as a promising agent for biocontrol of these destructive agricultural crop pests. Pasteuria ramosa, an obligate parasite of water fleas (Daphnia spp.), has been shown to modulate cladoceran populations in natural ecosystems. Selected sporulation genes and an epitope associated with the spore envelope of these related species were compared. The sigE and spoIIAA/spoIIAB genes differentiate the two species to a greater extent than 16S rRNA and may serve as probes to differentiate the species. Single-nucleotide variations were observed in several conserved genes of five distinct populations of P. ramosa, and while most of these variations are silent single-nucleotide polymorphisms, a few result in conservative amino acid substitutions. A monoclonal antibody directed against an adhesin epitope present on P. penetrans P20 endospores, previously determined to be specific for Pasteuria spp. associated with several phytopathogenic nematodes, also detects an epitope associated with P. ramosa endospores. Immunoblotting provided patterns that differentiate P. ramosa from other Pasteuria spp. This monoclonal antibody thus provides a probe with which to detect and discriminate endospores of different Pasteuria spp. The presence of a shared adhesin epitope in two species with such ecologically distant hosts suggests that there is an ancient and ecologically significant recognition process in these endospore-forming bacilli that contributes to the virulence of both species in their respective hosts.Pasteuria spp. are gram-positive endospore-forming obligate parasitic bacteria that have the unique distinction of being hosted by organisms in two distinct phyla, the Nematoda and the Arthropoda. These bacteria include parasites of phytopathogenic nematodes (4,5,13,16,19,24,26) and aquatic cladocerans (Moinidae and Daphinidae) (15) that suppress fecundity in populations occurring in natural environments. The ability of Pasteuria penetrans to suppress the growth of root knot nematodes supports its use as a benign alternative to chemical nematicides (6,8,11,12,18,20). Pasteuria ramosa, first described by Metchnikoff in 1888 (22), is as the type species of the genus Pasteuria. The planktonic crustacean Daphnia magna is a vital component of the food chain in freshwater ecosystems, and fluctuations in populations have a profound effect on pond ecology. As one of several naturally occurring parasites of the Daphnidae (16), P. ramosa is thought to play a significant role in the temporal distribution of Daphnia spp. in natural ecosystems (29).Species assignments for several phytopathogenic Pasteuria spp. and P. ramosa are based on 16S rRNA sequences, morphological properties of mature endospores, and host preferences (2,4,14,16,19,24). The phylogenetic relationships based on highly conserved sporulation transcription factors (24, 28, 31) and multiple genetic loci (9) further define the position of P. penetrans in relati...

Molecular Identification and Hidden Diversity of Novel Daphnia Parasites from European Lakes

“…Thus far, few species-specific molecular markers have been developed for Daphnia parasites (33,38,39,41) and then used in experimental studies (3). In surveys of natural Daphnia populations, parasite identification has been based primarily on microscopic examination (4,5,29,52), with only one exception (32).…”

Identification of New Single Nucleotide Polymorphism-Based Markers for Inter- and Intraspecies Discrimination of Obligate Bacterial Parasites (Pasteuria spp.) of Invertebrates

“…Previous studies have focused on the position of P. penetrans in the bacterial kingdom (9,31,34) and the use of consensus 16S rRNA gene sequences (6,7,18) to differentiate between species and populations of Pasteuria (5,16,33). However, this information has not been extensively supported with sequence data from protein-encoding genes, which potentially provide an additional source of discrimination, with the exception of one study examining partial coding sequences of some genes in P. ramosa populations (32), as well as a recent study of genes encoding collagen-like proteins in this species (22a).…”

Pasteuria penetrans and Its Parasitic Interaction with Plant Parasitic Nematodes

“…Vegetative bacteria can be destroyed, by exploiting the resistance of spores to enzymatic and chemical agents (Atibalentja et al 2000;Ebert et al 1996). The subsequent extraction of DNA from the spores is not without its problems, particularly because this needs to be optimized in view of the difficulty of obtaining sufficient spores in the first place; proprietary kits (Bekal et al 1999) or laboratory protocols involving chemical agents (Schmidt et al 2008) have been used, while bead-beating has also proven successful (Anderson et al 1999).…”

“…These authors were able to use this technique to demonstrate genetic differences between P. ramosa isolates in separate geographical locations and also to show within-population variations. Given the similarities in the genomes of the members of the genus Pasteuria (Schmidt et al 2008), it seems inevitable that the same technique will be applicable to other Pasteuria species.…”

“…Parasitized females produce few, if any, eggs (Bird and Brisbane 1988;Chen et al 1997). P. ramosa is, similarly, described as a castrating parasite of its water flea host (Schmidt et al 2008).…”