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Pdf: High Quality, but Uncorrected Proofs Family V. Pasteuriaceae Laurent 1890, 756AL Pas.teu.ri.a’ce.ae. N.L. fem. n. Pasteuria type genus of the family; suff. -aceae ending denoting family; N.L. fem. pl. n. Pasteuriaceae the family of Pasteuria. Gram-positive, dichotomously branching, septate mycelium, soil invertebrates. Has not been cultivated axenically, but can the terminal hyphae of which enlarge to form sporangia and be grown in the laboratory with its invertebrate host. eventually endospores. Nonmotile. Sporangia and microcolo- Type genus: Pasteuria Metchnikoff 1888, 166AL emend. Sayre nies are endoparasitic in the bodies of freshwater, plant, and and Starr 1985, 149; Starr and Sayre 1988a, 27. Genus I. Pasteuria Metchnikoff 1888, 166AL emend. Sayre and Starr 1985, 149; emend. Starr and Sayre 1988a, 27 [Nom. Cons. Opin. 61 Jud. Comm. 1986, 119. Not Pasteuria in the sense of Henrici and Johnson (1935), Hirsch (1972), or Staley (1973); see Starr et al. (1983) and Judicial Commission (1986)] RICHARD M. SAYRE AND MORTIMER P. STARR revised by DONALD W. DICKSON, JAMES F. PRESTON, III, ROBIN M. GIBLIN-DAVIS, GREGORY R. NOEL, DIETER EBERT AND GEORGE W. BIRD Pas.teu’ri.a. M.L. gen. n. Pasteuria of Pasteur, named after Louis Pasteur, French savant and scientist. Gram-positive, endospore-forming bacteria. Propagation fol- by Metchnikoff, this bacterium divides by budding. It forms a lowing germination within a nematode or cladoceran host pro- major non-prosthecate appendage (a fascicle), it does not form ceeds through the formation of rounded to elliptical (termed endospores, it is not mycelial or branching, its staining reaction “cauliflower-like” by Metchnikoff, 1888) vegetative microcolo- is Gram-negative, and it is not an endoparasite of cladocerans. nies from which “daughter” microcolonies may be formed. The After searching for, but not finding, the bacterial endopara- sporogenous cells at the periphery of the colonies are usually site in water fleas as described by Metchnikoff, the erroneous attached by narrow “sacrificial” intercalary hyphae that lyse, conclusion was reached that this budding bacterium that occurs resulting in developing sporangia arranged in clumps of eight on the surfaces of Daphnia species was the organism Metch- or more, but more often in quartets, triplets, or doublets and, nikoff had described in 1888. As a result, a budding bacterium finally, as single teardrop-shaped or cup-shaped or rhomboi- (strain ATCC 27377) was mistakenly designated (Staley, 1973) dal mature sporangia. The rounded end of the sporangium as the type culture for Pasteuria ramosa Metchnikoff (1888), the encloses a single refractile endospore (1.0–3.0 µm in major type (and, then, sole) species of the genus Pasteuria. This confu- dimension), an oblate spheroid, ellipsoidal or almost spherical sion between Metchnikoff’s described cladoceran parasite and in shape, usually resistant to desiccation and elevated tempera- the quite different budding bacterium was resolved by Starr et al. tures (one species has somewhat limited heat tolerance). Non- (1983). The budding bacterium (with strain ATCC 27377 as motile. Sporangia and microcolonies are endoparasitic in the its type culture) was named Planctomyces staleyi Starr, Sayre and bodies of freshwater, plant, and soil invertebrates. Axenic cul- Schmidt (1983), now named Pirellula staleyi (Butler et al., 2002). tivation has not been documented, but it can be grown in the Conservation of the original descriptions of the genus Pasteu- laboratory with its invertebrate host. The pathogen is horizon- ria and Pasteuria ramosa, as updated, was recommended (Starr tally transmitted via soil or waterborne spores. Infected hosts et al., 1983) and approved (Judicial-Commission, 1986). Unfor- fail to reproduce. tunately, vestiges of this nomenclatural disorder remained for DNA G+C content (mol%): not known. some time. For example, certain evolutionary and taxonomic Type species: Pasteuria ramosa Metchnikoff 1888, 166AL. inferences (Woese, 1987) regarding the genus Pasteuria were based upon data concerning bacteria belonging to the Blasto- Further descriptive information caulis–Planctomyces group of budding and non-prosthecately A complex of errors initially confused our understanding of the appendaged bacteria rather than the mycelial and endospore- genus Pasteuria Metchnikoff (1888). Stated briefly, Metchnikoff forming invertebrate parasites that actually comprise the genus (1888) described an endospore-forming bacterial parasite of Pasteuria. A Pasteuria ramosa-like strain was discovered infecting cladocerans, which he named Pasteuria ramosa. Metchnikoff the cladoceran Moina rectirostris, a member of the Daphniidae presented drawings and photomicrographs of the life stages of (Sayre et al., 1979), and this strain was used in the emendation this parasite as they occurred in the hemolymph of the water of the species (Starr et al., 1983). Ebert et al. (1996), however, fleas Daphnia pulex Leydig and Daphnia magna Straus. He was, proposed that the Daphnia-parasitic Pasteuria ramosa that they however, unable to cultivate the organism in vitro. Subsequent had characterized from the same host as Metchnikoff (1888) be workers (Henrici and Johnson, 1935; Hirsch, 1972; Staley, designated the neotype for Pasteuria ramosa Metchnikoff (1888) 1973), who were looking in cladocerans for Metchnikoff’s and that the Moina isolate be compared directly to the neotype unique bacterium, reported on a different bacterium with in future studies. only superficial resemblance to certain life stages of Pasteuria Confusion of a different kind occurred in the nomenclature ramosa. Their investigations led to the axenic cultivation of a of the bacterial endoparasite of nematodes when Cobb (1906) budding bacterium that is occasionally found on the exterior erroneously reported the numerous highly refractive bodies surfaces of Daphnia species. Unlike the organism described infecting specimens of the nematode Dorylaimus bulbiferous 339 BBergeys_Ch10.inddergeys_Ch10.indd 333939 22/19/2009/19/2009 77:49:55:49:55 PPMM 340 FAMILY V. PASTEURIACEAE as “perhaps monads” of a parasitic sporozoan. The incorrect However, Bacillus penetrans was not included in the Approved placement in the protozoa of an organism now known to be Lists of Bacterial Names (Skerman et al., 1980), therefore it a bacterial parasite of nematodes has persisted for nearly 70 had no nomenclatural standing. Although this micro-organism years. Another incorrect placement was suggested by Mico- forms endospores of the sort typical of the genus Bacillus Cohn letzky (1925), who found a nematode parasite similar in size (1872), its other traits (e.g., mycelial habit, endoparasitic asso- and shape to those reported by Cobb. Micoletzky suggested that ciations with plant-parasitic nematodes) suggested that it did this organism belonged to the genus Duboscqia Perez (1908), not belong in the genus Bacillus. Rather, it is closely related to another sporozoan group (Perez, 1908). Later, Thorne (1940) Pasteuria ramosa (see Table 55 and Figure 37) and it has more presented a detailed description of a new parasite from the properly been assigned (Sayre and Starr, 1985) to the genus nematode Pratylenchus pratensis (syn. Pratylenchus brachyurus, Pasteuria Metchnikoff (1888) as Pasteuria penetrans. see Sayre et al., 1988). Thorne assumed that this organism was The developmental stages that occur before sporulation are similar to the nematode parasite described by Micoletzky, similar for all Pasteuria spp. Except for Thermoactinomyces spp., thereby assigning it to the microsporidian genus Duboscqia, as the mycelial-like proliferation during development is not found Duboscqia penetrans. in any other endospore-forming bacteria. The morphological Thorne’s description and nomenclature persisted until 1975 changes that occur during sporulation appear to be generally even though other investigators (Canning, 1973; Williams, similar for all of the endospore-forming bacteria (Atibalentja 1960), who had examined this nematode parasite in some et al., 2004a, 2004b; Chen et al., 1997b; Ebert et al., 1996, 2004; detail, questioned this placement. It was not until the nematode Giblin-Davis et al., 2003a, 2003b; Metchnikoff, 1888; Sayre and parasite was re-examined using electron microscopy that its true Starr, 1985). affinities to bacteria rather than to protozoa were recognized Recent molecular work with 16S rRNA gene sequences sup- and the name Bacillus penetrans (Thorne, 1940) Mankau (1975) port Pasteuria as a monophyletic clade comprising well sup- was applied to it (Imbriani and Mankau, 1977; Mankau, 1975). ported lineages (Anderson et al., 1999; Atibalentja and Noel, TABLE 55. Common characteristics of Pasteuria ramosa Metchnikoff (1888), Pasteuria penetrans sensu stricto emend. Starr and Sayre (1988a), Pas- teuria thornei Starr and Sayre (1988a), Pasteuria nishizawae Sayre, Wergin, Schmidt and Starr (1991) emend. Noel, Atibalentja and Domier (2005), and “Candidatus Pasteuria usgae” Giblin-Davis, Williams, Bekal, Dickson, Brito, Becker and Preston (2003b) Characterisitic Description Morphological similarities as observed by light microscopy: Vegetative cells Microcolonies consist of dichotomously branched mycelium. Diameter of mycelial filaments similar. Mycelial filaments are seen in host tissues only during early stages of infection. Daughter microcolonies seem to be formed by lysis of “sacrifi- cial” intercalary cells. Nearly all vegetative mycelium eventually lyses, leaving only sporangia and endospores. Endospores Terminal hyphae
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