Bacteria of the sp. Bacillus that produce a lipopeptide are found to be effective in the treatment and prophylaxis of gastro-intestinal disease when administered as a probiotic. In particular, a strain of Bacillus bacteria identified as PB6 is useful for the treatment of Antibiotic Associated Diarrhea (AAD) or the more serious condition Clostridium difficile associated diarrhea (CDAD) when administered as a probiotic. Additionally, these bacteria have been found efficient for the treatment of immunorelated diseases such as Inflammatory Bowel Disease (IBD).