The adhesion of a recently described species, Acinetobacter venetianus VE-C3 (F. Di Cello, M. Pepi, F. Baldi, and R. Fani, Res. Microbiol. 148:237–249, 1997), to diesel fuel (a mixture of C12 to C28 n-alkanes) and n-hexadecane was studied and compared to that of Acinetobacter sp. strain RAG-1, which is known to excrete the emulsifying lipopolysaccharide, emulsan. Oxygen consumption rates, biomass, cell hydrophobicity, electrophoretic mobility, and zeta potential were measured for the two strains. The dropping-mercury electrode (DME) was used as an in situ adhesion sensor. In seawater, RAG-1 was hydrophobic, with an electrophoretic mobility (μ) of −0.38 × 10−8 m2 V−1 s−1 and zeta potential (ζ) of −4.9 mV, while VE-C3 was hydrophilic, with μ of −0.81 × 10−8 m2 V−1 s−1 and ζ of −10.5 mV. The microbial adhesion to hydrocarbon (MATH) test showed that RAG-1 was always hydrophobic whereas the hydrophilic VE-C3 strain became hydrophobic only after exposure to n-alkanes. Adhesion of VE-C3 cells to diesel fuel was partly due to the production of capsular polysaccharides (CPS), which were stained with the lectin concanavalin A (ConA) conjugated to fluorescein isothiocyanate and observed in situ by confocal microscopy. The emulsan from RAG-1, which was negative to ConA, was stained with Nile Red fluorochrome instead. Confocal microscope observations at different times showed that VE-C3 underwent two types of adhesion: (i) cell-to-cell interactions, preceding the cell adhesion to the n-alkane, and (ii) incorporation of nanodroplets of n-alkane into the hydrophilic CPS to form a more hydrophobic polysaccharide–n-alkane matrix surrounding the cell wall. The incorporation of n-alkanes as nanodroplets into the CPS of VE-C3 cells might ensure the partitioning of the bulk apolar phase between the aqueous medium and the outer cell membrane and thus sustain a continuous growth rate over a prolonged period.
展开▼
机译:最近描述的一种物种,即不动杆菌VE-C3(F. Di Cello,M. Pepi,F. Baldi和R. Fani,Res。Microbiol。148:237-249,1997),对柴油的粘附性(a研究了C12至C28正烷烃和正十六烷的混合物),并将其与不动杆菌属(Acinetobacter sp。)已知分泌乳化脂多糖乳油的RAG-1菌株。测量了这两种菌株的耗氧率,生物量,细胞疏水性,电泳迁移率和ζ电势。滴汞电极(DME)用作原位粘附传感器。 RAG-1在海水中具有疏水性,电泳迁移率(μ)为-0.38×10 -8 sup> m 2 sup> V -1 sup> s -1 sup>和ζ电势(ζ)为-4.9 mV,而VE-C3为亲水性,μ为-0.81×10 -8 sup> m 2 sup> V -1 sup> s -1 sup>,ζ为-10.5 mV。微生物对碳氢化合物的附着力(MATH)测试表明,RAG-1始终具有疏水性,而亲水性VE-C3菌株仅在暴露于正构烷烃后才变为疏水性。 VE-C3细胞与柴油的粘附性部分归因于荚膜多糖(CPS)的产生,荚膜多糖用与异硫氰酸荧光素缀合的凝集素伴刀豆球蛋白A(ConA)染色,并通过共聚焦显微镜原位观察。 RAG-1的乳胶(对ConA呈阴性)改为用尼罗红荧光染料染色。共聚焦显微镜在不同时间的观察结果表明,VE-C3经历了两种类型的粘附:(i)细胞与细胞之间的相互作用,先于细胞与正构烷烃的粘附,以及(ii)将正构烷烃的纳米液滴掺入亲水性CPS在细胞壁周围形成更具疏水性的多糖-正构烷烃基质。将正构烷烃作为纳米液滴掺入VE-C3细胞的CPS中,可以确保在水性介质和细胞外膜之间分配大量非极性相,从而在长期内保持连续的生长速率。
展开▼