(1), a study has been made of the validity of the gators. When examined by dark field microscopy

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1 SELENOMONAS BOSKAMP, 1922-A GENUS THAT INCLUDES SPECIES SHOWING AN UNUSUAL TYPE OF FLAGELLATION ERWIN F. LESSEL, JR. AND ROBERT S. BREED Cornell University, Geneva, New York In revising the 6th edition of Bergey's Manual and they have been so reported by a few investi- (1), a study has been made of the validity of the gators. When examined by dark field microscopy genus Selenwmas Boskamp (2). This generic and as stained by Giemsa's stain, the attachment name was introduced into the literature by von of the flagella in the center of the concave side Prowazek (3) in However, he did not name becomes clear. A highly refractive body within any species as belonging in the genus, and the the cell absorbs nuclear stains and apparently is name did not have a valid status until Boskamp a nuclear body. The cell structure and unique (2) described the species Selenomonas palpitans form of flagellation fully justify the recognition from the caecum of a guinea pig. This species of this species as the type species of a genus had been named earlier (1921) by Simons (4), distinct from Spirillum. but he failed to give a description so that the Because of the anaerobic nature of these ororganism did not receive a valid name until ganisms, investigators have not succeeded in Boskamp (2) published a description of it, cultivating them very readily, and their physioascribing the description to Simons. logical characteristics were not well known until The species mentioned above includes organ- Macdonald (5) succeeded in cultivating the isms that are unique in their type of flagellation. mouth organism anaerobically in reduced blood These organisms have been generally over- agar and Difco thioglycolate broth. looked as they are strictly anaerobic and do not Selenomonas palpitans apparently occurs not grow readily on the media that were used by only in the intestinal tract of guinea pigs, but early investigators. It is little wonder that a also in the intestine of related rodents and herpoorly described genus and a species introduced bivorous mammals. It, or a closely related into the literature with so little regard for the species, has been found by von Prowazek (3) in conventions established by codes of nomenclature examinations of blood contaminated with fecal have been so generally ignored. matter of gazelles, giraffes and antelope shot in Set8nomor palpitans is, however, a species in Africa (3). It has also been found in Brazil (6) which the organisms are sufficiently charac- in a rodent related to the guinea pig (Cavia teristic in their appearance and habitat to sperea) and in a deer (Caryacus sp.). make even a microscopic description adequate The recognition of the genus Selenomonas is for identification. The cells are of crescent form also indicated by the history of another species with blunt ends and are spirally twisted when of bacteria that has been known for an even they remain in chains. Thus they show the longer time than Selenomonas palpitans. In fact, normal appearance of organisms belonging to Dobell (7), in his book describing the work of the genus Spirillum. However, the cells are van Leeuwenhoek, feels confident that this motile with a curious tumbling type of motility organism was one of those found in the human different from that of the ordinary spirillum. mouth by this investigator in his original de- Staining with Giemsa's stain by von Prowazek scription of bacteria from the mouth. This 4,(3) revealed what appeared to be a single, red- species from the human mouth, which has been stained, very heavy flagellum attached at the named Spirillum sputigenum since 1886 (8), middle of the concave side of the cell. Further shows a tumbling, rotary motion. Because of studies showed this stout flagellum to be in this characteristic movement van Leeuwenhoek reality a tuft of perhaps a dozen individual was led to draw the path of this organism in his flagella. As shown in a related species from the original drawing as a curved, dotted line with a human mouth in separated form in electron loop in it (7). micrographs by Macdonald (5), the flagella may It has been difficult to determine who first readily be thought of as attached peritrichously, used the binomial Spirillum sputigenum. How- 165

2 166 ERWIN F. LESSEL, JR. AND ROBERT S. BREED [VOL. 18 ever, it seems probable that Miller, an American that they were like spirilla in many ways, dentist, originated the name during the course though they were doubtful whether they should of his work that resulted in the publication of his be regarded as bacteria. They concluded that inaugural dissertation from the University of these flagellated crescents were an unusual Berlin. Apparently Flugge (8) knew of Miller's primitive type and listed them as a sort of work and used the name (without giving its "Pro-flagellate". origin) in the second edition of his textbook The crescents from the rumen are described (1886). This is the first use of the binomial in the foregoing papers as having a morphology Spirillum sputigenum that we have found, and like that of the organisms placed in the genus it is accompanied by a description of the species. Selnomonas. They normally have a stout Miller's dissertation (9) was not published until flagellum attached in the center of the concave No copy of this has been found, but he side of the crescent, and the organisms divide by probably described SpiriUum sputigenum in it. transverse fission. When this happens, the At least he uses this binomial and describes this flagellum divides lengthwise and for a time the species in the various editions of his book on two flagella are attached near the blunt ends of mouth organisms (10) that is based on this the more or less pear-shaped young cells. The thesis. In subsequent literature Miller is usually flagella stain red with Giemsa's stain and then given as the author of this binomial. show that they are divided into fibrils as if the Miller did not succeed in cultivating this stout flagellum really represented a tuft of species from the human mouth, but he and flagella. The cells show several refractive bodies various other investigators studied it micro- flattened against the cell membrane; these scopically. It soon was established (11, 12, 13, granules stain with chromatin stains and may be 14) that this crescent-shaped organism had a nuclear in character. Occasionally the granules tuft of flagella attached laterally. This mor- lie underneath the point where the flagella are phology is exactly similar to that described for attached as is also stated to be true in Seleno- Selenomonas palpitans, and therefore Dobell (7) monas palpitans. placed Spirillum sputigenum in the genus Because Woodcock and Lapage (17) build up Selenomonas in The latter species, however, a doubtful life cycle for the rumen organisms was not well described until Macdonald (5) pub- and because other characteristics are not exactly lished his thesis. Like Selenomonas palpitans it is like those of Selenomonas sputigena or of Selenoa strict anaerobe. monas palpitans, the rumen species is accepted Protozoologists have reported the presence of for the present as a third species in Selenomonas. still another organism in the rumen juice of The movements of the rumen organisms are herbivorous mammals (cattle, sheep, deer and described in terms similar to those used in deespecially goats) that is similar to Selenomonas scribing the movements of the species previously sputigena and S. palpitans. Certes (15) observed placed in Selenomonas, and the body of the orthese in 1889 and, because of certain resem- ganism is reported to have the power of moveblances (S-form when in chains) to the protozoan ment independent of any action of the flagella. species Ancyromonas ides Kent, named On this account, the possibility that these orthese crescent-shaped forms Ancyromonas rumi- ganisms may have affinities with the spirochaetes nantium. is discussed (see next section). Kerandel (16) also found this so-called Ancy- Textbooks of protozoology by Wenyon (18) romonas in the blood of an antelope (Cephalophus and by Neveu-LeMaire (19) describe these unsp.) that was contaminated with stomach con- usual crescent-shaped organisms. Wenyon tents. The animal was shot in the Congo Region placed them in the genus Selenomonas under the of Africa. name Selenomonas ruminantium (Certes) Wen- Later Woodcock and Lapage (17) found these yon, and they are described under this name as organisms in the rumen juice of various domestic recently as 1948 by McGaughey and Sellers (20). animals and placed them in a new genus Selenomastix under the name Selenomastix ruminantium DISCUSSION (Certes) Woodcock and Lepage. The latter From this review it is evident that three quite authors were confident that the organisms in different groups of workers, (a) students of oral question were not true protozoa and reported bacteriology, (b) investigators of intestinal

3 1954] SELENOMONAS BOSKAMP 167 bacteriology, and (c) protozoologists, have all Prowazek (3) in 1913 has priority over Selenofound and named these flagellate organisms. The mastix that Woodcock and Lapage (17) proposed organism found in the human mouth has been the same year, the fact that von Prowazek did named Selenomonas sputigena and has been not name a species as belonging in the genus cultured anaerobically on Difco thioglycolate gives Selenomonas the status of a nomen nudum. media by Macdonald (5) in a way that demon- Nevertheless, Selenomonas von Prowazek has strates that it should be regarded as a bacterium. been accepted by some as having priority (18, The organism found in the rumen juice of her- 19, 20), and general usage has favored its acbivorous mammals has been named Selenomonas ceptance. Therefore, Selenomonas has been used ruminantium; it has not been cultured and is not in this discussion, while awaiting a review of the well known even to recent students of rumen status of the two names by the International bacteriology though it is well known to pro- Judicial Commission on Bacteriological Notozoologists. The organism found first in the menclature. caecum contents of guinea pigs (which is named Selenomonas palpitans) has later been shown to REFERENCES be common in the intestines of both rodents and 1. BREED, R. S., MURRAY, E. G. D., AND HITherbivorous mammals. As these bacteria swim CHENS, A. P Bergey's manual of by means of a tuft of flagella and have also been determinative bacteriology. 6th ed. The claimed to have the power to move independ- Williams & Wilkins Co., Baltimore, Md. ently of the flagella (2), they may well represent 2. BosKAmP, E Ueber Bau, Lebensweise organisms intermediate between Spirillum and und systematische Stellung von Selenomonas Spirochaeta, thus indicating a close relationship pi taen (ioab.n). CenI, Orakti Parabetween the species placed in Sillaceae and. VON PROWAZEK, S Zur Parasitologie those placed in Spirochaetroeae. von Westafrika. Centr. Bakt. Parasitenk., In view of the similar morphology and the Abt. I, Orig., 70, limited cultural studies that have been made on 4. SIMONs, H Ueber Selenomonas palthe three species included in this genus, it is, of pitans n. sp. Centr. Bakt. Parasitenk., course, possible that all of these species are Abt. I, Orig., 87, 50. identical; but for the present it is believed de- 5. MACDONALD, J. S The motile nonsirable to regard them as separate species. It sporulating anaerobic rods of the oral may even be possible that further studies may cavity. Thesis. University of Toronto. show that additional species should be recog DA pph nized. CUNHA, A. M Sobre apresenga de "Selenomonas" no coecum dos roedores. CONCLUSIONS Brasil Medico, 29, No. 5, 33. Selenomonas von Prowazek, 1913, emend. 7. DOBELL, C Antony van Leeuwenhoek Boskamp, 1922, is a recognizable genus and and his "little animals", p Harshould be accepted as such, type species Seleno- court, Brace, & Co., New York. monas palpitans Simons ex Boskamp, 1922, the 8. FLtGGE, C Die Mikroorganismen. 2 only species placed in the genus when it was Auf., Leipzig, valdlyspubieshaed.m this ienusw wasfirstd 9. MILLER, W. D Ueber pathogene validly published. This species was de- Mundpilze. Inaug. Diss., Berlin. scribed from the contents of the caecuml of 10. MILLER, W. D Die Mikroorganismen guinea pigs. A second species that belongs in der Mundhohle. 1 AuO., Leipzig; The the genus is Seenomnas sputigena (Flugge, microorganisms of the human mouth. Eng. 1886) Dobell, This species occurs in the ed., S. S. White Dental Mfg. Co., Philadelhuman mouth and may even have been seen by phia, 1890; 2 Aufl., Leipzig, van Leeuwenhoek in his studies of mouth or- 11- LOEWENTHAL, W Zur Kenntnis der ganisms in Still a third species has been Mundspirochiten. Med. Klinik, 2, 278- described by protozoologists as Selonaso HOFFMANN, HOFAN E., AND RWZK ruminantium (Certes, 1889) It is VON PROWAZEK, S foundminantieum(certesc Wenyon, Untersuchungen uber die Balanitis- und found i the ruinen jueie of herbivorous mam- MundspirochAten. Centr. Bakt. Parasiinals. The genus clearly belongs in the family tenk., Abt. I, Orig., 41, Spirillaceae Migula. 13. MUHLENS, P Ueber Zuchtung von Although Selenomonas as proposed by von anaeroben Mikroorganismen der Mundhohle

4 168 ERWIN F. LESSEL, JR. AND ROBERT S. BREED [VOL. 18 (u. a. Spirillum 8putigenum). Centr. Bakt. 17. WOODCOCK, H. M., AND LAPAGE, G On Parasitenk., Abt. I, Orig., 48, a remarkable type of protisten parasite. 14. YAMAMOTO, JUN Ueber den Lo- Quart. J. Micro. Sci., N.S., 59, komotionsapparat der Protistenzellen. 18. WENYON, C. M Protozoology, p Centr. Bakt. Parasitenk., Abt. I, Orig., 5S, Vol. 1. Bailliere, Tindall and Cox, London ~~~~~~~19. NEvEu-LEMAIRE, M TraitM de CERTES, A Note sur les micro-or- 1Nole M. 14 '. ~~~~~~~~~zoologieme~dicale et vdtdrinaire, traide p. protoganismes de la panse des ruminants. Bull Vigot Fr.res, Paris, soc. zool. France, 14, o M EY, 16. KERANDEL, J Sur quelques h6mato- 20. McGAUGHE, C. Pa., A., AND SELLERS, K. C. zaires observes au Congo. Bull. soc. path Microflora of the rumen. Nature, exotique., 2, , ADDENDUM The pictures on Plate I are photomicrographs of Selenomonas palpitans. They show flagella arising from the middle of the concave side of the organism and suggest that their insertion lies very close to, perhaps inside, the nucleus. The photographs reinforce the information contained in drawings of Selenomonas in the first detailed account of this species by Boskamp (1922). All figures are from preparations of the contents of the caecum of healthy guinea pigs. Figures 1-8. From caecum contents suspended in 5% formalin, washed by centrifugation and stained by Loeffler's method. The cells in figures 2 and 3 are preparing to divide. Figures 4-8. From wet films on coverslips fixed for 7 minutes in Schaudinn's fixative (without acetic acid). Stained with Giemsa solution. Figures 4 and 5 from films that had been treated for 10 minutes with N/1 HCl at 60 C before staining. Figures 6, 7 and 8 from directly stained films that had been differentiated in 20% alcohol (Dobell, 1911). All Giemsa preparations were photographed mounted in water. BOSKAMP, E Ueber Bau, Lebensweise und systematische Stellung von Selenomonas palpitans (Simons). Centr. Bakt. Parasitenk., Abt. I, Orig., 88, DOBELL, C. C Contributions to the cytology of the bacteria. Quart. J. Microscop. Sci., 56, 395. C. F. ROBINOW, Department of Bacteriology and Immunology, University of Western Ontario, London, Ontario, Canada.

5 PLATE I