Stromatolites are sedimentary rocks in the form of layered mounds, sheet like structures, columns and dome shaped structures. The primary composition of these sedimentary rocks is the limestone. These are found in the shallow waters and are usually formed by the cynobacteria and other single celled organisms such as algae and lichen.
The protease enzyme pepsin is found in the stomach and has a highly acidic PH of just 2, so the line would be at PH 2, so lower down than amylase which has a PH 7 :)
