Pasteuria penetrans and Its Parasitic Interaction with Plant Parasitic Nematodes

Abstract

Until quite recently, bacteriology has been the study of culturable organisms. The proportion of unculturable bacteria in the soil is commonly put at over 99% (Sharma et al. 2005). The ecology of many of these will be very difficult to discover (Nannipieri et al. 2003;Riesenfeld et al. 2004) but this is not the case for one extraordinary group of non-culturable, aerobic, spore-forming bacteria: members of the genus Pasteuria. The composite species are exclusively obligate parasites of either water fleas or plant parasitic nematodes. These represent the two lineages of the different species of Pasteuria. This chapter predominantly focuses on the nematode parasites because of their residence in soil.The first time that the characteristic spores of this genus were represented in publication were as drawings by Metchnikoff (1888) of what is now called Pasteuria ramosa (Ebert et al. 1996), the parasite of the water fleas Daphnia magna and D. pulex. This is now the type species of the genus Pasteuria and was recognized by Metchnikoff (1888) as an endospore-forming bacterium. A Pasteuria sp. was first reported in a nematode (Dorylaimus bulbiferous), by Cobb (1906), and the suggestion was made that it should be classified as a protozoan. In keeping with this suggestion the nematode parasite was later named Duboscqia penetrans by Thorne (1940) and placed in the family Microsporidiae.Until quite recently, developments in taxonomy were based solely upon observations and measurements made from electron micrographs. Mankau (1975) noted that the parasite of the root knot nematode (RKN) Meloidogyne javanica divided with the formation of cross walls reminiscent of bacteria, and that it formed spores similar to those of known endospore-formers. He suggested the adoption of a position within the eubacteria with the name Bacillus penetrans n. comb. In spite of the outlandish appearance of the highly differentiated vegetative phase (Fig. 9.1)

Scientific Opinion on the update of the list of QPS‐recommended biological agents intentionally added to food or feed as notified to EFSA†

“…Five species have been recognised: P. ramosa (which parasitises cladoceran water‐fleas), P . hartismeri , P. penetrans , P. thornei and P. nishizawae (parasitising plant pathogenic nematodes) based on their host range, morphology and 16S rRNA signatures (Bishop et al., , ). Since vegetative forms of P. nishizawae (and of any other nematode‐parasitic Pasteuria spp.)…”

“…All Pasteuria species described so far are obligate parasites of invertebrates, including plant parasitic nematodes and planktonic freshwater crustaceans of the genus Daphnia, and none have been grown in vitro. Five species have been recognised: P. ramosa (which parasitises cladoceran water-fleas), P. hartismeri, P. penetrans, P. thornei and P. nishizawae (parasitising plant pathogenic nematodes) based on their host range, morphology and 16S rRNA signatures (Bishop et al, 2007(Bishop et al, , 2011. Since vegetative forms of P. nishizawae (and of any other nematode-parasitic Pasteuria spp.)…”

“…Anonymous, 2014 (a) and EFSA webpage link (b) Additional information and QPS evaluation/comments Already . Qualification: Absence of toxigenic potential (see , 2011, 2012 (a) and EFSA webpage link (b) No sufficient body of knowledge and safety concern because of antibiotic production. Therefore not appropriate for QPS .…”

“…(a) and EFSA webpage link (b) Additional information and QPS evaluation/comments , 2007). Qualification: Absence of toxigenic potential (see , 2011, 2012 (a) and EFSA webpage link (b) Additional information and QPS evaluation/comments , 2007). Qualification: Absence of toxigenic potential (see , 2011, 2012.…”

“…Qualification: Absence of toxigenic potential (see , 2011, 2012 (a) and EFSA webpage link (b) Additional information and QPS evaluation/comments , 2007). Qualification: Absence of toxigenic potential (see , 2011, 2012. Re-evaluated in the current Scientific Opinion (refer to Section 3.2.1) with the conclusion: 'There is no requirement to change the QPS recommendation of the previously recommended Bacillus species, as the few infections associated with members of the genus were linked to specific predisposing factors and do not suggest a risk for consumers or animals via exposure through the food and feed chain'.…”