Isoelectric focusing of Bacteroides melaninogenicus group beta-lactamases

beta-Lactamases extracted by sonication from the Bacteroides melaninogenicus group organisms (B. asaccharolyticus, B. melaninogenicus, B. bivius, and B. oralis) were found to be in the form of complexes with molecular weights of greater than or equal to 40 x 10(6), and this resulted in failure to characterize them by isoelectric focusing. Purification by el filtration in the presence of deoxycholate resulted in beta-lactamase preparations from B. bivius with pI's of 5.7. A beta-lactamase preparation extracted by osmotic shock from B. bivius also had a pI of 5.7. Osmotic shock preparations from B. asaccharolyticus, B. melaninogenicus, and B. oralis had two bands of equal intensity with pI's of 4.2 and 4.35.