Genetic transformation of Veillonella parvula

Veillonellae are one of the most prevalent and predominant microorganisms in both the supra- and subgingival plaques of the human oral cavity. Veillonellae's mutualistic relationships with the early, middle, and late colonizers of the oral cavity make them an important component of oral biofilm ecology. Unlike other ubiquitous early colonizers in the oral cavity, surprisingly little is known about Veillonella biology due to our lack of ability to genetically transform this group of bacteria. The objective of this study was to test the transformability of veillonellae. Using Veillonella parvula strain PK1910, we first obtained spontaneous mutations conferring streptomycin resistance. These mutations all carry a K43N substitution in the RpsL protein. Using the mutated rpsL gene as a selection marker, a variety of conditions were tested and optimized for electroporation. With the optimized protocol, we were able to introduce the first targeted mutation into the chromosome of V. parvula PK1910. Although more studies are needed to develop a robust genetic manipulation system in veillonellae, our results demonstrated, for the first time, that V. parvula is transformable, at least for strain PK1910.