Let K be a knot in an L-space Y with a Dehn surgery to a surface bundle over S 1 . We prove that K is rationally fibered, that is, the knot complement admits a fibration over S 1 . As part of the proof, we show that if K ⊂ Y has a Dehn surgery to S 1 × S 2 , then K is rationally fibered. In the case that K admits some S 1 × S 2 surgery, K is Floer simple, that is, the rank of HF K(Y, K) is equal to the order of H1(Y ). By combining the latter two facts, we deduce that the induced contact structure on the ambient manifold Y is tight.In a different direction, we show that if K is a knot in an L-space Y , then any Thurston norm minimizing rational Seifert surface for K extends to a Thurston norm minimizing surface in the manifold obtained by the null surgery on K (i.e., the unique surgery on K with b1 > 0).It is a well-known fact that, up to isotopy, there exists a unique simple closed curve α on ∂ν(K) with the property that the surgery on K with slope α produces a manifold with the first Betti number one higher than that of Y . For simplicity of referring to this slope in the paper, we make the following definition: Definition 1.4. For a knot K ⊂ Y , let α be the unique slope on ∂ν(K) that is rationally nullhomologous in Y \ ν • (K). We call α the null slope of K in Y . We also define the null surgery on K to be Dehn filling the exterior of K in Y along the curve α and denote it Y α . Theorem 1.1 can be stated in terms of the dual knot K of L inside the L-space. More precisely, for an L-space Y , if the null surgery on K ⊂ Y results in S 1 × S 2 , then K is fibered. We generalize Theorem 1.1 by replacing S 1 × S 2 with an oriented closed three-manifold that is a surface bundle over S 1 . Compare the following theorem with [Ni07, Corollary 1.4].Theorem 1.5. Let K be a knot in an L-space Y . If the null surgery on K is a surface bundle over S 1 , then the complement of K in Y admits a fibration over S 1 .