Figure 5

Recombination within Haloferax volcanii biofilms. Two double auxotrophic strains (H53, ΔpyrE2/ΔtrpA; H98, ΔpyrE2/ΔhdrB) were mixed at equal cell densities and grown together in Hv-YPC + thymidine medium for 7 days under shaking conditions (black triangles), or as colony biofilms (green squares) and chamber slide SL-biofilms (green circles). Cultures and biofilms were then harvested, washed and plated on defined medium with uracil alone, to select for recombinants, which are either H53 cells that have regained tryptophan prototrophy through a transfer event with a H98 cell(s) or H98 cells that have gained thymidine prototrophy from a H53 cell(s). Average frequency of transfer is shown for three replicates per condition. The transfer frequency range reported in the study in which this HGT mechanism was discovered, traditionally conducted using nitrocellulose filters and known as mating, is shown as a grey box [56]. Vertical bars equal one standard deviation. HGT, horizontal gene transfer.