Please refer to Geo. Clifford White's excellent book, "Handbook of Chlorination". There is an extensive discussion on the chemistry of chlorination in this book. I sometimes refer to this book as the bible of chlorination.
Mr. White on page 266 of the book does make the statement, "Exactly how chlorine kills bacteria, cysts, and spores is still an academic puzzle. He goes on to indicate that there are six factors involved: (1) type of Cl residual fraction, (2) concentration, (3) contact time, (4) temperature, (5) type and concentration of organisms and (6) pH.