Magnesium aminoclay-based transformation of Paenibacillus riograndensis and Paenibacillus polymyxa and development of tools for gene expression.

Members of the genus Paenibacillus are widespread facultative anaerobic, endospore-forming bacteria. Some species such as Paenibacillus riograndensis or Paenibacillus polymyxa fix nitrogen and may play an important role in agriculture to reduce mineral nitrogen fertilization in particular for non-legume plants. The genetic manipulation of Paenibacillus is an imperative for the functional characterization, e.g., of its plant growth-promoting activities and metabolism. This study showed that P. riograndensis and P. polymyxa can be readily transformed using physical permeation by magnesium aminoclays. By means of the fluorescent reporter genes gfpUV, mcherry, and crimson, a two-plasmid system consisting of a theta-replicating plasmid and a rolling circle-replicating plasmid was shown to operate in both species. Xylose-inducible and mannitol-inducible fluorescent reporter gene expression was demonstrated in the compatible two-plasmid system by fluorescence-activated cell scanning. As a metabolic engineering application, the biotin requiring P. riograndensis was converted to a biotin-prototrophic strain based on mannitol-inducible expression of the biotin biosynthesis operon bioWAFDBI from Bacillus subtilis.