helping bodily processes has a positive impact on an animal / an animal 's health & a human is a kind of animal ->  helping bodily processes has a positive impact on a human  helping bodily processes has a positive impact on a human & digestion is a kind of bodily process ->  helping digestion has a positive impact on a human  helping digestion has a positive impact on a human & bacteria can help digest food in humans ->  some bacteria have a positive impact on humans by helping digestion  some bacteria have a positive impact on humans by helping digestion & if something has a positive impact on something else then that something is good for that something else ->  some bacteria are good for humans by helping digestion  some bacteria are good for humans by helping digestion & digestion is when stomach acid breaks down food -> some bacteria are good for humans by helping to break down food