Pseudomonas sp. DJ-12 cells were subjected to mild treatments of stress such as exposure to biphenyl, 4-chlorobiphenyl (4CB), 4-hydroxybenzoate (4HBA), ethanol, and heat, and then were examined for production of stress-shock proteins and morphological changes. The adapted cells were then subjected to lethal stress conditions such as 200 mM 4CB, 100 mM biphenyl, 10 mM 4HBA, 20% ethanol, and 46 degreesC to examine crossly protective responses to the stresses. Several stress-shock proteins including DnaK and GroEL were newly synthesized in the adapted cells. Some of them were commonly produced by those stresses separately treated. The cells treated with these aromatic hydrocarbons showed destructive openings on the cell envelopes. On the other hand, those cells treated with ethanol or heat displayed irregular rod shapes with wrinkled surfaces. The adapted cells to each stress under sublethal conditions exhibited increased resistance to the same stress of lethal conditions. The cells adapted with 5 mM 4HBA showed greater protection for survival than those adapted by other stresses. In addition, those adapted cells showed increased resistance to other stresses as a cross-protection phenomenon. The cells adapted to 42 degreesC exhibited markedly increased resistance to the lethal stresses of 46 degreesC as well as to 20% ethanol.