TABLE 3.

Quantification of Bdellovibrio plaques retrieved from soil, from the rhizosphere, and from total extracts of washed roots^a

Origin	Substrate cells	103 PFU · g−1b	Total bacterial counts on nutrient agar (CFU · g−1)b
Soil	P. corrugata PC	5.2 ± 0.85	2.3 × 107
Soil	E. carotovora subsp. carotovora 24	5.8 ± 0.52	2.3 × 107
Soil	A. tumefaciens C58	0.3 ± 0.09	2.3 × 107
Rhizosphere of common bean	P. corrugata PC	23 ± 1	1 × 108
Extract of washed roots of common beanc	P. corrugata PC	0.28 ± 0.05	5 × 107

^aRepresentative results of at least two experiments. 

^bPFU and CFU are expressed per gram (dry weight) of soil and per gram (fresh weight) of roots. 

^cRoots were thoroughly shaken and washed prior to grinding.