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Table 3 Effect of drastic selection with lethal drugs on the frequency of complementing types (CT) in the viable cell population of a Z-mating mixture between strains IL1 and MG407 differing by resistance to drugs and by nutritional requirements

From: Selection and evolution of mating products after spontaneous zygogenesis in Escherichia coli K-12

Exposure to KG

Colony count (Nt) after plating ona

Ratio Nt MG407-type /Nob

Ratio Nt CT /No b

Frequency of CT CFU among survivors (NtCT/Nt MG407type)

MA + P5 (IL1-type CFU)

LcA + UTT (MG407-type CFU)

LcA (CT CFU)

−

3.5 (±0.8) × 107

2.6 (±0.15) × 107

4.5 (±2.0) × 103

2.7 (±1.6) × 101

4.7 (±2.0) × 10−4

1.6 (±0.5) × 10−4

+

1.2 (±0.6) × 103

2.2 (±1.6) × 104

1.5 (±0.9) × 102

2.3 (±0.6) × 10−3

1.6 (±0.4) × 10−5

6.8 (±10.8) × 10−3

  1. aThe Szp+ strain MG407, marked with tetO array aac2, was mixed with the F− strain IL1, marked with lacO array aphII (respective average initial titres (No): 9.5 × 106 and 1.6 × 107 CFU mL−1). The 30-min mixture of ca. 5 × 107 bacteria in M9-LB was diluted twice in MLc for a 30-min incubation at 37 °C before addition (+) or not (−) of KG and an additional 3-h incubation. Plating was on the specified indicator media (P5: 200 μg hydrolysate of casein (“peptone 5”) mL−1 for growth of IL1-like bacteria; UTT: uracil + tryptophan + tyrosine for MG407-like bacteria). Values are means of four experiments
  2. bNo. of MG407, the minority parent. Average of the different frequencies
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Annals of Microbiology

ISSN: 1869-2044

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