Fig. 2.

Expansion of host range by ICE^Ac HGT. (A) Stem nodule formation. Stationary phase cultures of A. caulinodans (Ac), M. huakuii (Mh) and ICE^Ac-acquired M. huakuii (Mh::ICE^Ac) were applied on the surface of 6-wk-old S. rostrata stems and nodule formation was observed 30 d after inoculation (top panels). Bottom panels, transmission electron micrographs of stem nodules. Arrows, bacteroid. (B) The number and (C) the size of stem nodules formed 30 d after inoculation. (D) Nitrogenase activity in stem nodules. Nodules formed by inoculation of Ac, Mh and Mh::ICE^Ac were harvested and acetylene reduction activity was determined and the nitrogenase activity was calculated as % of acetylene production per gram of nodule dry weight. Data are mean ± SD of at least four independent experiments. ns, no significance; *P < 0.05.