title: Characterization of floating activity of indigenous diesel-assimilating bacterial isolates.
abstract: Six diesel-degrading bacterial strains were isolated from oil-polluted sites located in central Taiwan. The floating activity of the isolates in an oil-supplemented liquid medium was monitored. Cell-surface hydrophobicity as well as cell-free and cell-residue emulsification activities were also investigated. Three isolates, identified as Gordonia alkanivorans CC-JG 39, Rhodococcus erythropolis CC-BC 04, and R. erythropolis CC-BC 11, were found to float and grow near the diesel layer on the surface. The other three isolates (namely, Comamonas testosteroni CC-CF3, Acinetobacter sp. CC-CF 5, and Sphingomonas yanoikuyae CC-CG 22) did not display floating activity, as they distributed uniformly in the liquid medium. Isolated cell walls of the floating strains appeared to settle at a lower sucrose density than the non-floating strains. The floating strains were also characterized by a higher cell-surface hydrophobicity and a higher cell-residue emulsification activity than the non-floating strains. In fact, the floating strains were thought to produce extracellular emulsifiers due to their higher supernatant emulsification activity than the non-floating strains. The floating activity of G. alkanivorans CC-JG 39 may be associated with the production of extracellular polymeric substances that formed an "air-bag" structure facilitating cell floating. The floating ability may also correlate with a high cellular hydrophobicity arising from unique cell wall compositions or cell-wall-bound surface active products.
authors.affiliation: Department of Environmental Engineering, National Chung Hsing University, 250 Kuo-Kuang Road, Taichung 402, Taiwan.
authors.forename: Ta-Chen
authors.initials: TC
authors.lastname: Lin
authors.forename: Chiu-Chung
authors.initials: CC
authors.lastname: Young
authors.forename: Mann-Jing
authors.initials: MJ
authors.lastname: Ho
authors.forename: Mao-Song
authors.initials: MS
authors.lastname: Yeh
authors.forename: Chien-Liang
authors.initials: CL
authors.lastname: Chou
authors.forename: Yu-Hong
authors.initials: YH
authors.lastname: Wei
authors.forename: Jo-Shu
authors.initials: JS
authors.lastname: Chang
mesh_terms: D001419:Bacteria / Q000166:cytology / Q000254:growth & development* / Q000302:isolation & purification*; D018407:Bacterial Physiological Phenomena; D015169:Colony Count, Microbial; D005742:Gasoline / Q000382:microbiology*; D057927:Hydrophobic and Hydrophilic Interactions; D009038:Motion
chemical_list: D005742:Gasoline