Effects of crude oil on biomass and protein production by aquatic bacteria

Some effects of Bonny light crude oil on the biomass and protein production by three aquatic bacteria namely, Pseudomonas aeruginosa, Aeromonas hydrophyla and Vibrio fisheri were investigated. The species showed different responses to the toxic influences of various crude oil concentrations. The growth response was measured spectrophotometrically using optical density (OD) at 600nm. Pseudomonas aeruginosa responded positively to all crude oil levels. A general assessment indicated that 2% (v/v) crude oil concentration stimulated maximum biomass and protein production of this organism. Lower biomass and protein yields were observed at reduced crude oil levels. Biomass production decreased gradually among Aeromonas hydrophyla and Vibrio fisheri in comparison to the control. Biomass of Aeromonas hydrophyla increased from 0.1 (OD600nm) at 0 h to 0.58 after 20 h at 0.5% crude oil concentration. This level gradually declined to 0.03 after 20 h cultivation at 1.5 % crude oil concentration. Maximum decline in optical density of this organism was observed at crude oil concentration of 2.0%. Protein levels for Aeromonas hydrophyla decreased from 0.12 mg/mL after 20 h at crude oil concentration of 0.5% to 0.06 mg/mL after 20 h at maximum crude oil concentration of 2%. The biomass of Vibrio fisheri increased slightly from 0.1(OD600nm) at 0 h to 0.03 after 20 h at 0.5% crude oil level. Further decreases in OD values of this organism occurred progressively as the crude oil concentration was increased. Lowest protein yield for this organism was observed at a crude oil concentration of 2% at which the least protein production of 0.03 mg/mL was produced after 20 h cultivation.