TOXIC EFFECTS OF 2,4-D AND OTHER AROMATIC COMPOUNDS ON BACTERIA, AND THEIR PROTECTIVE RESPONSES

The purpose of this work was to investigate the induction of stress shock proteins (SSPs) in Burkholderia sp. YK-2 in response to 2,4-dichlorophenoxyacetic acid (2,4-D), and Pseudomonas sp. DJ-12 to benzoate, 4-chlorobenzoate (4-CBA), 4-hydroxybenzoate, and biphenyl. The SSPs, which contribute to the resistance of the cytotoxic effect of the toxic aromatic compounds including 2,4-D and 4-CBA, were induced at different concentrations of the compounds in exponentially growing cultures of Burkholderia sp. YK-2 or Pseudomonas sp. DJ-12. This response involved the induction of a 43 kDa DnaK and 41 kDa GroEL proteins in Burkholderia sp. YK-2, characterized by SDS-PAGE and Western blot using the anti-DnaK and anti-GroEL monoclonal antibodies. In Pseudomonas sp. DJ-12, 70 kDa DnaK and 60 kDa GroEL proteins was induced as SSPs, respectively. The total SSPs were analyzed by 2-D PAGE. Survival of Burkholderia sp. YK-2 or Pseudomonas sp. DJ-12 with time in the presence of different concentrations of the compounds was monitored, and viable counts paralleled the induction of the SSPs in these strains. Cells treated with the increased concentrations of toxic compounds showed some destructive openings on the cell envelopes.