Characterization of a heme oxygenase of Clostridium tetani and its possible role in oxygen tolerance

In order to colonize mammalian wounds, the anaerobic bacterium Clostridium tetani must presumably cope with temporary oxic conditions. Therefore, the recently decoded genome sequence was searched for genes which could confer oxygen tolerance. A few identified systems such as superoxide dismutases and peroxidases are probably responsible for this protection against toxic oxygen species. Another system was detected, a heme oxygenase which could have a role in establishing or maintaining an anoxic microenvironment in the process of wound colonization. The hemT gene encoding the heme oxygenase is expressed in C. tetani, as shown by reverse transcription-PCR. When overexpressed in Escherichia coli, the enzyme converts heme to biliverdin under strict oxic conditions.