Bacterial spores, from ecology to biotechnology.

The production of a highly specialized cell structure called a spore is a remarkable example of a survival strategy displayed by bacteria in response to challenging environmental conditions. The detailed analysis and description of the process of sporulation in selected model organisms have generated a solid background to understand the cellular processes leading to the formation of this specialized cell. However, much less is known regarding the ecology of spore-formers. This research gap needs to be filled as the feature of resistance has important implications not only on the survival of spore-formers and their ecology, but also on the use of spores for environmental prospection and biotechnological applications.

Optimization of alkaline protease production by rational deletion of sporulation related genes in Bacillus licheniformis.

BACKGROUND: Our laboratory has constructed a Bacillus licheniformis strain that secretes alkaline protease (AprE) with excellent enzymatic properties. B. licheniformis is generally regarded as safe and has a high industrial exoenzyme secretion capacity, but the host retains some undomesticated characteristic that increase its competitiveness and survival, such as spore-formation, which increases the requirements and difficulties in industrial operations (e.g. sterilization and enzyme activity control). Furthermore, the influence of sporulation on alkaline protease production in B. licheniformis has not been elucidated in detail. RESULT: A series of asporogenic variants of the parent strain were constructed by individually knocking out the master regulator genes (spo0A, sigF and sigE) involved in sporulation. Most of the variants formed abortively disporic cells characterized by asymmetric septa at the poles and unable to survive incubation at 75 °C for 10 min. Two of them (ΔsigF and ΔsigE) exhibited superior characteristics in protease production, especially improving the expression of the aprE gene. Under the currently used fermentation conditions, the vegetative production phase of ΔsigF can be prolonged to 72 h, and the highest protease production of ΔsigF reached 29,494 ± 1053 U/mL, which was about 19.7% higher than that of the wild-type strain. CONCLUSION: We first constructed three key sporulation-deficient strain to investigate the effect of sporulation on alkaline protease synthesis. The sigF mutant retained important industrial properties such as facilitating the sterilization process, a prolonged stable phase of enzyme production and slower decreasing trend, which will be superior in energy conservation, simpler operations and target product controlling effect. In summary, the work provides a useful industrial host with preferable characteristics and a novel strategy to enhance the production of protease.