Key words: bacteria, multiple response, mixture of hydrocarbons. These modifications differ from one strain to another and even for the same bacterial strain, according to the nature of hydrophobic substrate. There were observed cellular and molecular modifications induced by mixture of saturated, monoaromatic and polyaromatic hydrocarbons to Gram-positive and Gram-negative bacteria. Isolated Gram-negative bacteria were more tolerant to mixture of saturated ( n-hexane, n-hexadecane, cyclohexane), monoaromatic (benzene, toluene, ethylbenzene) and polyaromatic (naphthalene, 2-methylnaphthalene, fluorene) hydrocarbons than Gram-positive bacteria. IBB Po12) bacteria, isolated from oily sludge, were found to be able to tolerate pure and mixture of saturated hydrocarbons, as well as pure and mixture of monoaromatic and polyaromatic hydrocarbons. IBB Po3) and Gram-negative ( Chryseomonas sp. In present study Gram-positive ( Mycobacterium sp. Most of our knowledge about pollutants and the way they are biodegraded in the environment has previously been shaped by laboratory studies using hydrocarbon-degrading bacterial strains isolated from polluted sites. Independentei St, 060031, PO 56-53, Bucharest, Romania Multiple responses of gram-positive and gram-negative bacteria to mixture of hydrocarbonsД¬enter of Microbiology, Institute of Biology, Romanian Academy, 296 Spl. These modifications differ from one strain to another and even for the same bacterial strain, according to the nature of hydrophobic substrate.Д«acteria multiple response mixture of hydrocarbons Isolated Gram-negative bacteria were more tolerant to mixture of saturated (n-hexane, n-hexadecane, cyclohexane), monoaromatic (benzene, toluene, ethylbenzene) and polyaromatic (naphthalene, 2-methylnaphthalene, fluorene) hydrocarbons than Gram-positive bacteria. IBB Po3) and Gram-negative (Chryseomonas sp. In present study Gram-positive (Mycobacterium sp.

Gram positive vs gram negative