Table 1. Morphological characteristics of four strains of PAOs

Morphology characteristics	A1	A2	A3	A5
Colony shape	Circular	Oval	Circular	Circular
Surface	Wet	Wet	Wet	Rough
Edge	Entire	Entire	Erose	Entire
Color	White milk	Pink	White milk	White milk
Gram staining	Gram-negative		Gram-negative	Gram-negative

PAO, phosphate-accumulating organism.