Systems biology of recombinant protein production using Bacillus megaterium.

The Gram-negative bacterium Escherichia coli is the most widely used production host for recombinant proteins in both academia and industry. The Gram-positive bacterium Bacillus megaterium represents an increasingly used alternative for high yield intra- and extracellular protein synthesis. During the past two decades, multiple tools including gene expression plasmids and production strains have been developed. Introduction of free replicating and integrative plasmids into B. megaterium is possible via protoplasts transformation or transconjugation. Using His(6)- and Strepll affinity tags, the intra- or extracellular produced proteins can easily be purified in one-step procedures. Different gene expression systems based on the xylose controlled promoter P-xylA and various phage RNA polymerase (T7, SP6, K1E) driven systems enable B. megaterium to produce up to 1.25 g of recombinant protein per liter. Biomass concentrations of up to 80 g/l can be achieved by high cell density cultivations in bioreactors. Gene knockouts and gene replacements in B. megaterium are possible via an optimized gene disruption system. For a safe application in industry, sporulation and protease-deficient as well as UV-sensitive mutants are available. With the help of the recently published B. megaterium genome sequence, it is possible to characterize bottle necks in the protein production process via systems biology approaches based on transcriptome, proteome, metabolome, and fluxome data. The bioinformatical platform (Megabac, http://www.megabac.tu-bs.de) integrates obtained theoretical and experimental data.