Strontium resistance was investigated in strains isolated from the river Kzlrmak which has been affected by industrial and agricultural heavy metal pollution from the surrounding facilities and domestic effluents from the city Krkkale, Turkey. Strontium-resistant isolates with a minimal inhibitory concentration of 2000mg L-1 were isolated and identified as Pseudomonas fluorescens and Sphingomonas paucimobilis. Both isolates were shown to be resistant to other heavy metals like aluminum, lithium, barium, nickel and resistance to the antibiotics like aztreonam and pefloxacin. Plasmid DNA analysis, transformation and curing results revealed that the strontium resistance ability of both isolates was chromosome-encoded. Outer membrane and total protein isolation results descriptively showed that not only membrane porins but also other proteins were effective in the strontium resistance in Pseudomonas fluorescens and Sphingomonas paucimobilis.