“The mammalian gut is home to hundreds of bacterial species that contribute to food digestion and, in some cases, inflammatory gut diseases. Probiotics, beneficial bacterial species, can enhance gut health by keeping the resident bacteria in check. Now, a team of researchers at the RIKEN Innovation Center in Wako, including Mitsuharu Matsumoto, report that administration of the probiotic bacterial strain Bifidobacterium animalis subspecies lactis LKM512 to mice can lengthen their lifespan.
Matsumoto and colleagues previously showed that LKM512 could reduce inflammatory markers in elderly humans and modify the makeup of intestinal bacteria2, but the effects of it on lifespan still required investigation. After starting 10-month-old mice on a diet including LKM512 for 11 months, the researchers found that LKM512-treated mice lived longer, had fewer skin lesions, and had better hair quality than untreated mice.
Analyses of the gut of these mice revealed elevated gene expression in some bacterial species compared with control mice, indicating that LKM512 may improve gut health indirectly by regulating the levels of other bacterial species. The LKM512 treatment also prevented some age-related changes in bacterial composition of the gut, suggesting that the probiotic treatment protects the gut from developing characteristics associated with aging….”
The Bovine 
That is an interesting study they did on mice, wonder if they will move the probiotics studies eventually onto humans?