Construction of a high-efficiency shuttle vector for Histophilus somni

The genetic manipulation of Histophilus somni is limited due to its high-fidelity restriction-modification system. The broad host-range shuttle plasmid pLS88 is capable of transforming some strains of H. somni, but is an inefficient vector. We have constructed an improved version of pLS88, pNS3K, that transforms H. somni strain 2336 100-fold more efficiently than its predecessor. The transformation efficiency was further increased when pNS3K was isolated from H. somni and retransformed into the same strain. As proof of principle, the lipooligosaccharide biosynthesis gene lob-2A was cloned into pNS3K and expressed in H. somni strain 129Pt, which lacks this gene. Thus, pNS3K is a useful shuttle vector for H. somni and a potential vector for genetic manipulation of this bacterium.