The Inhibition of Growth or Cell Division in Escherichia coli by Different Ionic Species of Platinum(IV) Complexes

When a solution containing the complex ion, [PtCl6]=, and NH4+ ions is irradiated, a photochemical change occurs in which the chloride ions of the ligand are sequentially replaced by 1, 2, or 3 ammonia molecules. The total charge on the complex ion decreases by 1 negative charge for each replacement. These changes can be followed by changes occurring in absorption spectra or in ionophoretic patterns. Each charged species of the complex has a unique effect on the bacteriological growth of Escherichia coli. The doubly negative species is a bacteriocide. The singly negative species appears to have little effect on either growth or cell division processes. The neutral species has little effect on growth, but markedly inhibits cell division processes, forcing filamentous growth. The cis and trans forms of the diamino complex, [PtCl4(NH3)2]0, have been synthesized. The absorption spectra of both have a λmax at 207 mµ. The electrophoretic patterns indicate predominantly neutral species in both cases. The trans form is relatively inefficient in inhibiting cell division, whereas the cis form is fully as efficient as the neutral species in inhibiting cell division. We identify the neutral species as the cis form of the complex.