Pasteuria penetrans (ex Thorne 1940) nom. rev., comb. n., sp. n., a mycelial endospore-forming bacterium parasitic in plant-parasitic nematodes
Sayre, RM.; Starr, MP.
Proceedings of the Helminthological Society of Washington 522: 149-165
A spore-forming parasite of plant-parasitic nematodes, at first believed to be a sporozoan, was later recognized to be a bacterium and was renamed Bacillus penetrans (Thorne, 1940) Mankau, 1975. Because B. penetrans was not included in the 1980 Approved Lists of Bacterial Names, it has no taxonomic standing. In effecting the formalities incident to reviving lapsed bacterial names, it became clear that B. penetrans was misassigned to the bacaterial genus Bacillus Cohn, 1872. Although the mode of formation and the structure of the endoscope of the nematode parasite are similar to that described for members of the genus Bacillus, the organism differs from the description of that genus in cellular shape and size, motility, flagellation, sporangial shape and size, habitat and nutritional requirements. The following traits of the nematode parasite suggest that it more properly belongs in the genus Pasteuria Metchnikoff, 1888: primary vegetative colonies consist of a dichotomously branched, septate mycelium; daughter colonies, formed by fragmentation, gradually contain fewer but larger cells arranged predominantly in quartets; these larger vegetative cells differentiate into sporangia, arranged in quartets and doublets; eventually, single sporangia predominate in the nematode's pseudocoelom; the sporangium consists of a conical stem, a swollen middle cell,and an endogenous spore; the mature endospores, released from the remnants of the nematode, attach to the cuticles of other host nematodes and germinate; then, the parasitic cycle is repeated. A description of Pasteuria penetrans (ex Thorne, 1940) revived name, comb-nov. sp. nov. and an emended description of the genus Pasteuria are presented.