A group of bicyclists are crossing a bridge.
Cyclists cross over a bridge together.
Cyclists is plural so implies a group of bicyclists. "Over a bridge" is a rephrasing of "crossing a bridge". Doing something together implies it is done in a group.
exists e1 x1 x2 x3.(Theme(e1,x3) & Actor(e1,x1) & v_cross(e1) & n_bridge(x3) & of(x1,x2) & n_bicyclist(x2) & n_group(x1))
exists e1 s1 x1 x2.(a_together(s1) & Manner(e1,s1) & over(e1,x2) & n_bridge(x2) & Actor(e1,x1) & v_cross(e1) & n_cyclist(x1))