Menezes Bento Fátima, de Oliveira Camargo Flavio A, Okeke Benedict C, Frankenberger William T
Departament of Soils, University of Rio Grande Sul, Porto Alegre, CEP 91590-900, RS, Brazil.
Microbiol Res. 2005;160(3):249-55. doi: 10.1016/j.micres.2004.08.005.
Biosurfactant production is a desirable property of hydrocarbon-degrading microorganisms (HDM). We characterized biosurfactant producing microbial populations from a Long Beach soil, California (USA) and a Hong Kong soil (China), contaminated with diesel oil. A total of 33 hydrocarbon-utilizing microorganisms were isolated from the soils. Twelve isolates and three defined consortia were tested for biosurfactant production and emulsification activity. The highest reduction of surface tension was achieved with a consortium of L1, L2 and L3 isolates from a Long Beach soil (41.4mN m(-1)). Isolate L1 (Acinetobacter junii) displayed the highest reduction of surface tension (46.5 mN m(-1)). The emulsifying capacity evaluated by the E24 emulsification index was highest in the culture of isolate L5 (74%). No substantial emulsification was achieved with the cell-free extracts, indicating that the emulsifying activity was not extracellular. Based on surface tension and the E24 index results, isolates F1, F2, F3, F4, L1, L2, L3 and L4 were identified by 16S rRNA gene sequencing as Bacillus cereus, Bacillus sphaericus, B. fusiformis, Acinetobacter junii, a non-cultured bacterium, Pseudomonas sp. and B. pumilus, respectively. Cluster analyses of 16S rRNA gene sequences of the bacterial isolates revealed 70% similarity amongst hydrocarbon-degrading bacterial community present in both soils. Five isolates (isolates F1, F2, F3, F4 and L4) belong to the Firmicutes order, two isolates (L1 and L3) belong to the Proteobacteria order and one isolate (L2) is an Actinomyces sp. Simpson's index (1 - D) and the Shannon-Weaver index (H) revealed more diversity of HDM in the Hong Kong soil, while evenness (E) and the equitability (J) data indicated that there was not a dominant population. Bacterial isolates displaying substantial potential for production of biosurfactants can be applied in the bioremediation of soils contaminated with petroleum hydrocarbons.
生物表面活性剂的产生是烃降解微生物（HDM）的一个理想特性。我们对来自美国加利福尼亚州长滩土壤和中国香港土壤中被柴油污染的产生生物表面活性剂的微生物群落进行了表征。从这些土壤中总共分离出33种利用烃的微生物。对12株分离菌和3个确定的菌群进行了生物表面活性剂产生和乳化活性测试。来自长滩土壤的L1、L2和L3分离菌组成的菌群使表面张力降低幅度最大（41.4mN m(-1)）。分离菌L1（琼氏不动杆菌）使表面张力降低幅度最大（46.5 mN m(-1)）。通过E24乳化指数评估的乳化能力在分离菌L5的培养物中最高（74%）。无细胞提取物未实现显著乳化，表明乳化活性不是胞外的。基于表面张力和E24指数结果，通过16S rRNA基因测序将分离菌F1、F2、F3、F4、L1、L2、L3和L4分别鉴定为蜡样芽孢杆菌、球形芽孢杆菌、梭形芽孢杆菌、琼氏不动杆菌、一种未培养细菌、假单胞菌属和短小芽孢杆菌。对细菌分离菌的16S rRNA基因序列进行聚类分析显示，两种土壤中存在的烃降解细菌群落之间有70%的相似性。5株分离菌（分离菌F1、F2、F3、F4和L4）属于厚壁菌门，2株分离菌（L1和L3）属于变形菌门，1株分离菌（L2）是放线菌属。辛普森指数（1 - D）和香农 - 韦弗指数（H）显示香港土壤中HDM的多样性更高，而均匀度（E）和公平性（J）数据表明不存在优势种群。显示出具有产生生物表面活性剂巨大潜力的细菌分离菌可应用于被石油烃污染土壤的生物修复。
