Lysinibacillus capsici 38,328 isolated from agricultural soils as a promising probiotic candidate for intestinal health

There is an increasing interest in the use of spore-forming Bacillus spp. as probiotic ingredients on the market. However, probiotics Bacillus species are insufficient, and more safe Bacillus species were required. In the study, traditional fermented foods and soil samples were collected from more than ten provinces in China, and 506 Bacillus were selected from 109 samples. Using the optimized procedure, we screened nine strains, which successfully passed the acid, alkali, bile salt, and trypsin resistance test. Drug sensitivity test results showed that three Bacillus out of the nine isolates exhibited antibiotic sensitivity to more than 29 antibiotics. The three strains sensitive to antibiotics were identified by 16S ribosomal RNA, recA, and gyrB gene analysis, two isolates (38,327 and 38,328) belong to the species Lysinibacillus capsici and one isolate (37,326) belong to Bacillus halotolerans. Moreover, the three strains were confirmed safe through animal experiments. Finally, L. capsici 38,327 and 38,328 showed protections in the Salmonella typhimurium infection mouse model, which slowed down weight loss, reduced bacterial load, and improved antioxidant capacity. Altogether, our data demonstrated that selected L. capsici strains can be used as novel probiotics for intestinal health.

Automated summary

In this study, traditional fermented foods and soil samples were collected from various provinces in China, leading to the selection of 9 Bacillus strains that passed resistance tests for acid, alkali, bile salt, and trypsin. Out of these, 3 strains showed antibiotic sensitivity to more than 29 antibiotics. Gene analysis confirmed that these 3 strains belong to Lysinibacillus capsici and Bacillus halotolerans. Animal experiments confirmed their safety, and L. capsici 38,327 and 38,328 exhibited protective effects in a Salmonella typhimurium infection mouse model. These findings suggest that selected L. capsici strains can be used as novel probiotics for intestinal health.