DNA, a Possible Site of Action of Aluminum in Rhizobium spp.

Al was found to penetrate the cell envelopes of both sensitive and tolerant Rhizobium strains and bind to DNA in vivo. Despite causing a reduction in viability, Al stimulated DNA synthesis in the sensitive strain, which suggested that an excision repair mechanism was operating. The Al-stimulated DNA synthesis was reduced by the simultaneous addition of chloramphenicol. In contrast to the sensitive strain, DNA synthesis was unaffected by Al binding to DNA in the tolerant strain. It is proposed that Al enters the cell and binds to the DNA helix, increasing stabilization and preventing successful replication. Different repair mechanisms appear to operate in response to Al in tolerant and sensitive strains.