Hoefel D, Ho L, Aunkofer W, Monis P T, Keegan A, Newcombe G, Saint C P
The Cooperative Research Centre for Water Quality and Treatment, Australian Water Quality Centre, SA Water Corporation, Salisbury, South Australia, Australia.
Lett Appl Microbiol. 2006 Oct;43(4):417-23. doi: 10.1111/j.1472-765X.2006.01974.x.
To isolate and identify bacteria from a sand filter column capable of degrading the taste and odour compound, geosmin. In doing so, to investigate if these organisms degrade geosmin either individually or if an alternative mechanism is utilized.
Geosmin-degrading bacteria from a biologically active sand filter column were enriched by their growth in a minimal medium supplemented with geosmin as the sole carbon source. By day 51, 21.7 mg l(-1) of geosmin had been degraded as determined by solid-phase microextraction gas chromatography/mass spectrometry, and was accompanied by a 2.12 log(10) increase in active bacterial numbers as measured using the BacLight(TM) bacterial viability kit and flow cytometric enumeration. During the onset of geosmin degradation, the predominance of three bacteria, most similar to previously cultured species of Sphingopyxis alaskensis, Novosphingobium stygiae and Pseudomonas veronii based on 16S rRNA gene sequences was detected by denaturing gradient gel electrophoresis. Subsequent isolation of these organisms revealed that degradation of geosmin, when present as either the sole carbon source (ranging from 40 ng l(-1) to 20 mg l(-1)) or when spiked into sterile reservoir water (37 and 131 ng l(-1)), occurred only when all three isolates were present. None of the isolates was shown to be capable of degrading geosmin either individually or in any combination of two.
This study has reported, for the first time, the cooperative degradation of geosmin by a consortium comprising three gram-negative bacteria isolated from a biologically active sand filter column.
These results are important for researchers currently employing molecular-based approaches to further understand the biodegradation of geosmin by bacteria, as such studies may be complicated by the discovery of geosmin degradation occurring by a consortium. This study also advances the knowledge surrounding the types of bacteria capable of degrading the taste and odour compound, as investigations to date regarding this are limited.
从能够降解土臭素（一种引起味觉和嗅觉的化合物）的砂滤柱中分离并鉴定细菌。在此过程中，研究这些微生物是单独降解土臭素，还是利用了其他机制。
通过在以土臭素作为唯一碳源的基本培养基中生长，对来自生物活性砂滤柱的土臭素降解细菌进行富集培养。到第51天时，通过固相微萃取气相色谱/质谱法测定，21.7 mg l(-1)的土臭素已被降解，同时使用BacLight(TM)细菌活力试剂盒和流式细胞术计数法测得活性细菌数量增加了2.12 log(10)。在土臭素降解开始时，通过变性梯度凝胶电泳检测到三种细菌占优势，基于16S rRNA基因序列，它们与先前培养的阿拉斯加鞘氨醇单胞菌、斯氏新鞘氨醇单胞菌和维罗纳假单胞菌最为相似。随后对这些微生物的分离表明，只有当所有三种分离株都存在时，土臭素作为唯一碳源（浓度范围为40 ng l(-1)至20 mg l(-1)）或添加到无菌储水中（37和131 ng l(-1)）时才会发生降解。没有一个分离株被证明能够单独或两种组合降解土臭素。
本研究首次报道了由从生物活性砂滤柱中分离出的三种革兰氏阴性细菌组成的联合体对土臭素的协同降解作用。
这些结果对于目前采用基于分子的方法来进一步了解细菌对土臭素生物降解的研究人员很重要，因为此类研究可能会因发现联合体对土臭素的降解而变得复杂。本研究还推进了关于能够降解味觉和嗅觉化合物的细菌类型的知识，因为迄今为止对此的研究有限。
