Bacteria are the smallest known living things with a cellular structure. These colorless, one-celled micro-organisms exist (31)________organic matter is found: in soil, in water and in the air. Since most of them have no chlorophyll, they cannot use light energy to synthesize their food, (32)_________green plants do.They must get their food in other ways. In this, bacteria resemble animals. However, since they are enclosed in a cell wall, they can only (33)_________dissolved food like plants do. Although most bacteria do not contain chlorophyll, some of them can make their own organic food from simple inorganic (34)________. They do not, however, use light energy for this purpose. Others get ready-made food from dead plants and animals. Still others are parasites. Parasites are (35)________to enter other living organisms and take food from them. In doing so, they often cause diseases or the death of their hosts.