Zhang Y, Miller R M
Department of Soil and Water Science, University of Arizona, Tucson 85721.
Appl Environ Microbiol. 1994 Jun;60(6):2101-6. doi: 10.1128/aem.60.6.2101-2106.1994.
In this study, the effect of a purified rhamnolipid biosurfactant on the hydrophobicity of octadecane-degrading cells was investigated to determine whether differences in rates of octadecane biodegradation resulting from the addition of rhamnolipid to four strains of Pseudomonas aeruginosa could be related to measured differences in hydrophobicity. Cell hydrophobicity was determined by a modified bacterial adherence to hydrocarbon (BATH) assay. Bacterial adherence to hydrocarbon quantitates the preference of cell surfaces for the aqueous phase or the aqueous-hexadecane interface in a two-phase system of water and hexadecane. On the basis of octadecane biodegradation in the absence of rhamnolipid, the four bacterial strains were divided into two groups: the fast degraders (ATCC 15442 and ATCC 27853), which had high cell hydrophobicities (74 and 55% adherence to hexadecane, respectively), and the slow degraders (ATCC 9027 and NRRL 3198), which had low cell hydrophobicities (27 and 40%, respectively). Although in all cases rhamnolipid increased the aqueous dispersion of octadecane at least 10(4)-fold, at low rhamnolipid concentrations (0.6 mM), biodegradation by all four strains was initially inhibited for at least 100 h relative to controls. At high rhamnolipid concentrations (6 mM), biodegradation by the fast degraders was slightly inhibited relative to controls, but the biodegradation by the slow degraders was enhanced relative to controls. Measurement of cell hydrophobicity showed that rhamnolipids increased the cell hydrophobicity of the slow degraders but had no effect on the cell hydrophobicity of the fast degraders. The rate at which the cells became hydrophobic was found to depend on the rhamnolipid concentration and was directly related to the rate of octadecane biodegradation.(ABSTRACT TRUNCATED AT 250 WORDS)
在本研究中，研究了纯化的鼠李糖脂生物表面活性剂对十八烷降解细胞疏水性的影响，以确定向四株铜绿假单胞菌中添加鼠李糖脂后十八烷生物降解速率的差异是否与所测得的疏水性差异有关。细胞疏水性通过改良的细菌对烃类的粘附（BATH）测定法来确定。细菌对烃类的粘附定量了在水和十六烷的两相系统中细胞表面对水相或水 - 十六烷界面的偏好。根据在无鼠李糖脂情况下的十八烷生物降解情况，将这四株细菌分为两组：快速降解菌（ATCC 15442和ATCC 27853），其细胞疏水性较高（分别为74%和55%的十六烷粘附率），以及慢速降解菌（ATCC 9027和NRRL 3198），其细胞疏水性较低（分别为27%和40%）。尽管在所有情况下鼠李糖脂都使十八烷的水分散度增加了至少10^4倍，但在低鼠李糖脂浓度（0.6 mM）下，相对于对照，所有四株菌株的生物降解最初至少被抑制100小时。在高鼠李糖脂浓度（6 mM）下，快速降解菌的生物降解相对于对照略有抑制，但慢速降解菌的生物降解相对于对照有所增强。细胞疏水性的测量表明，鼠李糖脂增加了慢速降解菌的细胞疏水性，但对快速降解菌的细胞疏水性没有影响。发现细胞变得疏水的速率取决于鼠李糖脂浓度，并且与十八烷生物降解速率直接相关。（摘要截短于250字）
