704 MANUAL OF DETERMINATIVE BACTERIOLOGY 



FAMILY XIII. BACILLACEAE FISCHER.* 



(Jahrb. f. wiss. Bot., 27, 1895, 139.) 



Rod-shaped cells, capable of producing spores, either with peritrichous flagella or 

 non-motile ; monotrichous flagellation has been reported but is doubtful. Endospores 

 are cylindrical, ellipsoidal or spherical, and are located in the center of the cell, 

 sub-terminally or terminally. Sporangia do not differ from the vegetative cells except 

 when bulged by spores larger than the cell diameter. Such sporangia are spindle- 

 shaped when spores are central, or wedge- or drumstick-shaped when spores are 

 terminal. Usually Gram-positive. Pigment formation is rare. Aerobic, microaero- 

 philic or anaerobic. Gelatin is frequently liquefied. Sugars are generally fermented, 

 sometimes with the formation of visible gas. Some species are thermophilic, i.e., 

 will grow readily at 55°C. Mostly saprophytes, commonly found in soil. A few are 

 animal, especially insect, parasites or pathogens. 



Key to the genera of family Bacillaceae. 



I. Aerobic; catalase positive. 



Genus I. Bacillus, p. 705. 

 II. Anaerobic or microaerophilic ; catalase not known to be produced. 



Genus II. Clostridium, p. 763. 



INTRODUCTION TO THE GENUS BACILLUS. 



In the fifth edition of the Manual, the late F. D. Chester stated: "It is difficult to 

 offer a rational system of classification for the described forms of the genus Bacillus 

 because of the incompleteness of the data". He prepared a splendid review of the 

 literature but naturally could not supply the data that were missing. He stated 

 further that "The majority of the so-called species in the genus have been imperfectly 

 presented, . . . the net result being that there are comparatively few clearly and 

 definitely described species among the many herein recorded. The development of a 

 better knowledge will be a work of the future". He then discussed the type of work 

 that should be done. A reading of his statement is recommended to anyone contem- 

 plating naming a new species. 



During the past few years, the writer with the assistance of Francis E. Clark and 

 Ruth E. Gordon has made a study of the genus Bacillus along the lines indicated by 

 Chester. Representative cultures have been obtained from various laboratories, 

 institutions, and private collections. Special mention should be made of the private 

 collection of Prof. J. R. Porter, now at the Iowa State University. It contained about 

 200 named species and was invaluable for the work. As a result of this study, it ap- 

 pears that many species have been differentiated by such simple characters as mucoid, 

 folded, adherent or rhizoid growth, pigment production, the fermentation of a specific 

 carbohydrate, etc. Others have been grouped because of some special physiological 

 activity such as the decomposition of calcium n-butyrate, xylan, cellulose, etc. Ches- 

 ter rightly considered that these physiological groups had no taxonomic value. 



Species have been characterized upon a broad basis in the present arrangement on 

 the assumption that one species should not dissociate into another species. Since 

 certain characters are more stable than others, these have been used to establish a 



* Revised by Mr. Nathan R. Smith, U. S. Bureau of Plant Industry Station, Belts- 

 ville, Maryland (Bacillus), August, 1943, and Prof. R. S. Spray, School of Medicine, 

 West Virginia University, Morgantown, West Virginia {Clostridium) , May, 1942. 



