Bacillus Subtilis Delays Neurodegeneration and Behavioral Impairment in the Alzheimer’s Disease Model Caenorhabditis Elegans

Abstract

Multiple causes, apart from genetic inheritance, predispose to the production and aggregation of amyloid-β (Aβ) peptide and Alzheimer’s disease (AD) development in the older population. There is currently no therapy or medicine to prevent or delay AD progression. One novel strategy against AD might involve the use of psychobiotics, probiotic gut bacteria with specific mental health benefits. Here, we report the neuronal and behavioral protective effects of the probiotic bacterium Bacillus subtilis in a Caenorhabditis elegans AD model. Aging and neuronal deterioration constitute important risk factors for AD development, and we showed that B. subtilis significantly delayed both detrimental processes in the wild-type C. elegans strain N2 compared with N2 worms colonized by the non-probiotic Escherichia coli OP50 strain. Importantly, B. subtilis alleviated the AD-related paralysis phenotype of the transgenic C. elegans strains CL2120 and GMC101 that express, in body wall muscle cells, the toxic peptides Aβ_3-42 and Aβ_1-42, respectively. B. subtilis-colonized CL2355 worms were protected from the behavioral deficits (e.g., poor chemotactic response and decreased body bends) produced by pan-neuronal Aβ_1-42 expression. Notably, B. subtilis restored the lifespan level of C. elegans strains that express Aβ to values similar to the life expectancy of the wild-type strain N2 fed on E. coli OP50 cells. The B. subtilis proficiencies in quorum-sensing peptide (i.e., the Competence Sporulation Factor, CSF) synthesis and gut-associated biofilm formation (related to the anti-aging effect of the probiotic) play a crucial role in the anti-AD effects of B. subtilis. These novel results are discussed in the context of how B. subtilis might exert its beneficial effects from the gut to the brain of people with or at risk of developing AD.