In contrast , in participants with initial butyrate concentrations < 25 mmol/kg of wet feces , the probiotic contributed to a 329 255 % ( mean SD ) increment in butyrate concomitantly with an 55 % decrease in Ruminococcus ( P = 0.016 ) and a 150 % increase in an abundantly represented unclassified Bacteroidales genus ( P = 0.05 ) .