For a knot $K$ in $\mathbb{S}^{3}$, Kakimizu introduced a simplicial
complex whose vertices are all the isotopy classes of minimal
genus spanning surfaces for $K$. The first purpose of this
paper is to prove the $1$-skeleton of this complex has diameter
bounded by a function quadratic in knot genus, whenever $K$
is atoroidal. The second purpose of this paper is to prove
the intersection number of two minimal genus spanning surfaces
for $K$ is also bounded by a function quadratic in knot genus,
whenever $K$ is atoroidal. As one application, we prove the
simple connectivity of Kakimizu's complex among all atoroidal
genus $1$ knots.