This dissertation had studied the differences between chemical and biological reaction of DBP production and provide a mechanistic understanding for the sources of precursors under which DBP formation varies. This study had covered: (1) The formation of DBPs during chlorination due to biological effects studied; (2) the protein expression so as to study the potential mechanisms and further to develop possible methods to predict DBP formation; and (3) bacterial response to antibiotics in biofilm. The relationship of two prevalent bacteria and four common metal elements were studied. And the separation of intracellular organic matter, extracellular organic matters and pure culture organic matters clearly showed the differences in DBP distribution among them. The results imply that (1) the correlation between cells and metals possesses potential mechanism to influence DBP formation; (2) metal-related proteins such as metal-binding proteins and metal activated transporters on membranes could be potential DBP precursors; (3) Bacterial community could be influenced by environmental pressures such as antibiotics. This study proved that bacterial organic matters could be very possible DBP precursors with comparison between in vivo bacterial cells and extracted organic matters; and the addition of metals assisted my research to exploit potential cellular mechanism inside cells. And antibiotic resistant biofilm validated some aspects of biological response that possibly relate to DBP formation. This study of the formation of DBPs could be benefited not only for better water treatment, but also for studies of bio-resistance, bio-metabolism and artificial biochemical compounds.