TABLE 3.

Generation of transductants using different values for the donor strains (lysogens of phages) and the recipient strain (E. coli WG5) in the food samples without mitomycin C induction^a

Donor strain and no. of CFU (10X)	No. of recipient strain CFU (10Y)	Threshold (X + Y)b	Presence of transductants ind:
			Water	Milk	Beef	Salad	LB medium
C600φ3538
108	108	16	+b	+	+	+	+
	106	14	+	+	+	+	+
	104	12	+	+	+	+/−	+
	102	10	−	−	−	−	+
107	107	14	+	+	+	+	+
106	106	12	+	+	+	+	+
105	105	10	+	+	+	+	+
104	104	8	+	+	+/−	+/−	+
103	103	6-7c	+/−	−	−	−	+/−
102	102	4-5c	−	−	−	−	−
LysφA557Cm
107	106	13	+	+	+	+	+
	104	11	+	+	+	+
	102	9	−	+/−	−	−	+
106	108	14	+	+	+	+	+
	106	12	+	+	+	+	+
105	105	10	+	+	+/−	−	+
104	104	8	+	+/−	−	−	+
103	103	6-7c	+	+/−	−	−	+/−
102	102	4-5c	−	−	−	−	−
101	101	2-3c	−	−			−
Lys933WCm
107	107	14	+	+	+	+	+
	106	13	+	+	−	−	+
	105	12	−	−	−	−
106	107	13	+	+	+	+	+
	106	12	−	−	−	−

^aNumbers of CFU ml⁻¹ or g⁻¹ of sample were measured for the donor and recipient strains.

^bThe threshold necessary for the generation of transductants was estimated and is expressed as the sum of X + Y, where X is the exponential value for the donor strain and Y is the exponential value for the recipient strain.

^cWhen using lower values of donor and recipient cells, the X + Y calculation varies with the replicas and is expressed as a range between two log units.

^d+, transductants were generated, unless otherwise indicated, at >10³ CFU ml⁻¹ or g⁻¹ of sample; +/−, some replicas positive and some negative; −, no transductants.