Table 1.

Triparental gene transfer rates in A. eutrophus biofilms as a function of cell contact time, helper cell density, and nutrient concentration

MediumContact time (h)Triparental gene transfer rate in biofilm (no. of transconjugants/recipient cell/h)a
102 helper cells added108 helper cells added
100% LB22.4 × 10−3 A7.5 × 10−4 E
247.1 × 10−4 AB9.1 × 10−4 E
1% LB21.2 × 10−3 AB3.4 × 10−3 D
242.5 × 10−4 B5.8 × 10−4 E
  • a The total volumes analyzed per treatment were 1.8 × 106 μm3 for slides with 108 helper cells (25 vertical stacks of images with 10 x-y optical sections and a volume of 7.3 × 104 μm3 per stack) and 3.7 × 106 μm3 for slides with 102helper cells (50 vertical stacks). For each set, means with different letters are significantly different at P ≤ 0.05 by the Student-Newman-Keuls pairwise multiple comparison method.