Bacteroides are now recognized as major pathogens in various infections especially in those consequent to bowel surgery which is frequently if not primarily due to cancer of the colon. These bacteria cause extensive tissue destruction and considerable mortality in such cases. Yet, little is known of their mechanisms of pathogenesis or of what converts quiescent intestinal commensals to destructive invaders. We have now isolated and partialy characterized two different endotoxin-like lipopolysaccharides from most species of this genus which we plan to further characterize chemically, biologically and as to their possible involvement in pathogenesis. We will - in this context - study what role anaerobic growth conditions may exert on the chemical nature of such substances which are similar to but subtly distinct from endotoxins familiar in "aerobic" bacteria. We will pursue our fortuitous observations that we may be able to greatly speed up diagnosis of Bacteroides infections by either or both of two methods - detection of characteristic enzymes in aspirates from surgical sites before clinical signs are evident, and/or pyrolysis-GLC of cells from colonies on initial-isolation-plates. Lastly, we will more closely examine B. melaninogenicus with respect to its curious enzymatic disparity as compared with other members of this genus.