their characteristics, and the conditions of culture
were described previously (22).
Extraction of crude LPS. The crude S-LPS (fM)
was extracted from 60 g of acetone-dried cells of B.
abortus strain 11-19 with hot phenol-water (Fig. 1) as
described by M. S. Redfearn (Ph.D. thesis, University
of Wisconsin-Madison, Madison, Wis., 1960) and
Baker and Wilson (2).
The crude R-LPS (RM) from B. abortus strain 45/
20 was prepared by the following method (Fig. 2): 60
g of acetone-dried cells was extracted for protein with
2.5% NaCl at 40C (23). The supernatant fluids were
separated from the cells by centrifugation at 8,000 x
g for 30 min at 40C. The wet cells were frozen and
stored for 4 weeks at -20°C. The cells were then
washed and dried in acetone, and batches of 7 g were
extracted with chloroform-petroleum ether-phenol as
described by Galanos et al. (12). The batches of cell
residue were kept for further extraction. The super-