Catalase negative mutants ofHelicobacter pylori

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Abstract
Nine strains ofHelicobacter pylori have been isolated exhibiting spontaneous mutations with a loss of catalase activity. Growth characteristics in vitro were unaffected by the mutation showing that catalase is not essential for growth ofHelicobacter pylori. Parent strains and mutants could not be distinguished morphologically from each other when compared by electron microscopy. Restriction endonuclease digestion withHindIII, separated in an 0.7 % agarose gel in TBE buffer, showed each pair to be highly related to each other. SDS-PAGE separation of proteins from four mutants and parent strains showed that all mutants lacked a 57 kDa protein. The partial N-terminal sequence of this protein shows homology with maize catalase and may be the subunit of theHelicobacter pylori catalase tetramer. It is concluded that catalase negative mutants ofHelicobacter pylori occur spontaneously in vitro, but have not yet been observed in vivo. The paucity of such catalase negative strains in clinical specimens could mean that catalase is a virulence factor in vivo that puts mutants at a selective disadvantage.