Date of Award:


Document Type:


Degree Name:

Doctor of Philosophy (PhD)



Department name when degree awarded

Bacteriology and Public Health

Committee Chair(s)

Fred J. Post


Fred J. Post


Lewis W. Jones


Paul B. Carter


During bacteriological studies of the Logan City Sewage Oxidation Ponds, Logan, Utah, a group of bacteria was discovered which could lyse killed cells of Escherichia coli. The present research effort was an attempt to determine whether two isolates from this earlier study might play a role in the reduction of coliforms and other bacteria in the oxidation ponds. It was also desired to characterize partially the lytic enzymes produced by the two isolates and to determine as far as possible the organisms' identity.

Both isolates were Gram negative rod-shaped organisms with a single polar flagellum. On Cytophaga agar they produced small, circular, yellow-pigmentecl colonies. The optimum temperature for growth of both isolates was found to be 20 C. Both isolates exhibited proteolytic activity but lacked any lipolytic ability. On the basis of these and other characteristics, the two isolates were tentatively placed in the genus Xanthomonas.

By the use of an agar overlay technique, it was shown that both isolates could lyse a wide variety of bacteria. Those genera which were lysed to the greatest extent were Citrobacter, Enterobacter, Escherichia and Salmonella. Neither of the isolates were able to lyse bacteria belonging to the genera Corynebacterium, Leuconostoc, Neisseria or Streptococcus. Generally the isolates showed greater lytic ability against Gram negative bacteria than against Gram positive bacteria.

By concentrating the growth liquor containing the lytic enzyme and testing its lytic ability, it was determined that the optimum pH for lysis of autoclaved E. coli cells for the enzyme from one isolate was approximately pH 8.0, and pH 7.5 for the other. The optimum temperature for lysis by the enzymes from both isolates was found to be 20 C.

All attempts to show lysis of live bacteria were unsuccessful. Thus the role of these two organisms in the ecology of waste treatment ponds would probably be that of a scavenger on dead or killed cells and would not affect the population of live coliforms or other bacteria.



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