Team:HZAU-China/Project/Bacillus subtilis as Probiotics

• Overview
• The innovation of HZAU-iGEM Team
• The design of experiment
• Rabies
• Flea and Yersinia pestis
• Bacterial Spores as Vaccine Vehicles
• Bacillus subtilis as Probiotics
• Antimicrobial Peptides

Probiotics are live microbes, which confer a health benefit to the host when administered in adequate amounts. Immune stimulation, antimicrobial activities and competitive exclusion make Bacillus species a good application in probiotic. For a long time, Bacillus species are considered soil organisms. However, it is problematic to isolate the vegetative bacteria from soil. Studies show that a percentage (>10%) of an inoculums of B.subtilis spores can complete its sporulation and vegetative cell growth cycle in small intestine. An intestinal habitat of spores formers helps explain why spores can be found in the gut of insects, animals and humans. Using analysis of both biopsies and faeces, Bacilli can be obtained from the human GI-tract(). Other studies show similar results. B.subtilis was considered to be of greater importance than other commensal bacteria in gut-associated lymphoid tissue development. So these results suggest that B.subtilis should be considered as gut commensals. Meanwhile, the property of the secretion of antimicrobials provide a probiotic effect through suppressing the growth of competing microbes as well as enteric pathogens. B.subtilis can suppress infection with pathogenic S. enteric, C.perfringens and E.colic.

The following picture shows the condition of the internal environment of flea.

We want to modify the bacteria that exist in the internal environment of flea in the beginning. Bacillus sp. exists in the internal environment of flea. And the above results show that B.subitilis is gut commesals. Meanwhile, the secretion of antimicrobials of B.subitilis will play an important role in making flea safe enough. So we think that bacillus subtilis is appropriate for our design.

Reference

1. M.Cutting S. Bacillus probiotics. Food Microbiology, 2011;28:214-220.

2. Murrell A, J.Dobson S et al. A survey of bacterial diversity in ticks, lice and fleas from Australia. Parasitol Res, 2003;89:326-334.