Cell envelope stress responses upon protein overproduction in Bacillus subtilis

PhD ceremony: Ms. B.C. Marciniak, 16.15 uur, Academiegebouw, Broerstraat 5, Groningen

Dissertation: Cell envelope stress responses upon protein overproduction in Bacillus subtilis

Promotor(s): prof. O.P. Kuipers

Faculty: Mathematics and Natural Sciences

The thesis of Bogusia Marciniak provides knowledge on mechanisms responding to membrane and secreted protein overproduction stress, which can be used for further improvement of Bacillus subtilis as a protein production host. Moreover, it offers insight in the role of the cre boxes in determining the strength of carbon catabolism regulation by CcpA.

B. subtilis and its relatives are used to produce more than half of the commercially available enzymes used for the detergent-, food- and beverage industries and for the development of pharmaceuticals. Despite of previous improvement of B. subtilis as a production host by manipulations of the limiting factors that hamper different stages of protein production or secretion, enzyme production can still be difficult.

In this thesis stress responses activated under intensive production of homo- and heterologous proteins are identified. A specific membrane stress response involving a putative membrane protease was characterized and a novel negative regulator of this response was identified. Also indispensability of the PrsA foldase/chaperone responsible for correct folding of secreted proteins was investigated. PrsA was shown to be essential due to its indirect involvement in lateral cell wall biosynthesis. Moreover, B. subtilis is able to maximize its metabolic efficiency through regulation of carbon metabolism genes by a global regulator, CcpA, which binds to operator sequences named cre boxes. This is relevant for industry for optimization of cell cultivation in big fermentations. cre boxes were analyzed on a genome-wide scale. Differences in cre sequences and positions in relation to transcriptional start sites appeared to determine their regulatory efficiencies.