Growth of small free-living amoebae in various bacterial and in bacteria-free cultures.

Abstract

Hartmannella glebae, H. agricola, and Naegleria gruberi fed on a Flavobacterium sp. developed tolerance for the yellow pigment. Differences in the formation of plaques in the bacterial growth and in the growth cycle were observed.Various species of bacteria were equally effective as food for all three amoebae, and richness of the amoeba cultures paralleled the richness of the growth of edible bacteria. Failure of Pseudomonas pyocyanea to support growth of these amoebae was attributed to the toxicity of the pyocyanin pigment, and inability of the amoebae to develop tolerance to this pigment was attributed to the relatively high solubility of the pigment in water.These amoebae showed no growth on agar in the absence of living edible bacteria; however, bacteria-free H. agricola and N. gruberi, but not H. glebae, were successfully maintained in monkey kidney tissue cultures. The amoebae exhibited no toxic effect on the epithelial cells and fed on cell debris. Ingestion of very large numbers of cysts by young cells or any number by old cells resulted in degeneration of the cells with a release of live cysts. Epithelial cell degeneration hastened by enteroviruses facilitated rapid growth of the amoebae.