Deciphering the mechanisms of action underlying probiotic properties of Shouchella clausii by a functional genomics approach.

Probiotics are widely used for their health promoting effects, though a lot remain to be discovered, particularly on their mechanisms of action at the molecular level. The functional genomic approach is an appropriate method to decipher how probiotics may influence human cell fate and therefore contribute to their health benefit. In the present work, we focused on Shouchella clausii (formerly named Bacillus then Alkalihalobacillus clausii), a spore-forming bacterium that is commercially available as a probiotic for the prevention and the treatment of intestinal dysbiosis and related gastrointestinal disorders, such as diarrhoea.

Greedy reduction of Bacillus subtilis genome yields emergent phenotypes of high resistance to a DNA damaging agent and low evolvability.

Genome-scale engineering enables rational removal of dispensable genes in chassis genomes. Deviating from this approach, we applied greedy accumulation of deletions of large dispensable regions in the Bacillus subtilis genome, yielding a library of 298 strains with genomes reduced up to 1.48 Mb in size.

The coordinated population redistribution between submerged biofilm and liquid-air pellicle.

is a widely used bacterial model to decipher biofilm formation, genetic determinants and their regulation. For several years, studies were conducted on colonies or pellicles formed at the interface with air, but more recent works showed that non-domesticated strains were able to form thick and structured biofilms on submerged surfaces. Taking advantage of time-lapse confocal laser scanning microscopy, we monitored bacterial colonization on the surface and observed an unexpected biphasic submerged biofilm development.

Bacterial growth physiology and RNA metabolism.

Bacteria are sophisticated systems with high capacity and flexibility to adapt to various environmental conditions. Each prokaryote however possesses a defined metabolic network, which sets its overall metabolic capacity, and therefore the maximal growth rate that can be reached. To achieve optimal growth, bacteria adopt various molecular strategies to optimally adjust gene expression and optimize resource allocation according to the nutrient availability.

Constitutive Stringent Response Restores Viability of Bacillus subtilis Lacking Structural Maintenance of Chromosome Protein.

Bacillus subtilis mutants lacking the SMC-ScpAB complex are severely impaired for chromosome condensation and partitioning, DNA repair, and cells are not viable under standard laboratory conditions. We isolated suppressor mutations that restored the capacity of a smc deletion mutant (Δsmc) to grow under standard conditions. These suppressor mutations reduced chromosome segregation defects and abrogated hypersensitivity to gyrase inhibitors of Δsmc.