<Tr> <Td> Enterobacter sp . </Td> <Td> 40--80 </Td> </Tr> <Tr> <Td> Klebsiella sp . </Td> <Td> 40--80 </Td> </Tr> <Tr> <Td> Bifidobacterium bifidum </Td> <Td> 30--70 </Td> </Tr> <Tr> <Td> Staphylococcus aureus </Td> <Td> 30--50 </Td> </Tr>

Where are microorganisms normally found in the digestive system