554 THE ANAEROBIC BACTERIA 
or near the center of the parent celh Their diameter is usually about 
1 micron, and their length about 1.5 micron. Less commonly, the 
spores are subterminal. The spores are very frequently obser^'ed free 
from the bacillary body. Young, active cultures, and organisms 
stained directly in pathological tissue and fluids, are Gram-positive, 
but the staining becomes irregular in older cultures. The bacilli 
readily stain with the ordinary anilin dyes. 
Isolation and Culture.— B. sporogenes belongs to the group of obligate 
anaerobic bacteria, but the organism is somewhat less exacting in its 
anaerobic requirements than some members of this group. 
It grows readily upon ordinary cultural media in the absence of air, 
and the colonies upon agar are dense, filamentous masses of bacilli with 
delicate outgrowths which are readily observed with the lower powers 
of the microscope. The colonies may reach a diameter of several 
millimeters. Submerged colonies are dense, opaque and flocculent. 
The optimum reaction for growth is approximately that of the blood 
(pH 7.5) but growth will occur if the initial reaction varies between 
slight acidity (pH 6.5) to decided alkalinity (pH 8.5). A noteworthy 
feature of the organism is its ability to grow symbiotically with B. 
welchii, Vibrion septique, B. tetani, B. putrificus, and others. "Pure 
mixed cultures" of these organisms with B. sporogenes may exist 
unsuspected for years in stock cultures. It is no exaggeration to state 
that much of the confusion surrounding the apparent proteolytic 
activity of cultures of the Welch bacillus, B. tetani, B. botulinus, B. 
putrificus, Mbrion septique, the organism of symptomatic anthrax, 
and others, has been caused by the unsuspected presence of B. sporo- 
genes as a contaminant in stock cultures of these bacteria. The pecu- 
liar fermentative and putrefactive cycles of B. saccharobutyricus immo- 
bilis of Grassberger and Schattenfroh,i of B. enteritidis sporogenes of 
Klein^ and others, is attributable to admixture of the active fermen- 
tative organism (B. welchii), which asserts itself in sugar-containing 
media, with the passive B. sporogenes, which becomes prominent in 
media from which carbohydrates are excluded. There appears to be no 
very satisfactory method of separating B. sporogenes from other 
organisms with which it will grow symbiotically except that of isolating 
single spores by the modified Barber method.^ 
Conditions of Growth.— B. sporogenes is an obligate anaerobe, but it 
will develop in the presence of oxygen in amounts which would be 
inhibitory for other members of the anaerobic group. Growth is 
vigorous at 37° C. and its range of growth is a wide one. The maximum 
is about 42° (\, the minimum about 18° C. 
Products of Growth. — Gelatin, casein, egg, medium and coagulated 
serum are liquefied, and there is a considerable production of ammonia 
1 Arch. f. Hyg., 1902, 42, 219. 
2 Centralbl. f. Bakteriol., 1895, 18, 737; 1897, 22, 577. 
' See Anaerobic Methods, p. 240. 
