Uyttebroek Maarten, Breugelmans Philip, Janssen Mieke, Wattiau Pierre, Joffe Boris, Karlson Ulrich, Ortega-Calvo Jose-Julio, Bastiaens Leen, Ryngaert Annemie, Hausner Martina, Springael Dirk
Division Soil and Water Management, Catholic University of Leuven, Kasteelpark Arenberg 20, B-3001 Leuven, Belgium.
Environ Microbiol. 2006 May;8(5):836-47. doi: 10.1111/j.1462-2920.2005.00970.x.
Summary Mycobacterium is often isolated from polycyclic aromatic hydrocarbon (PAH)-contaminated soil as degraders of PAHs. In model systems, Mycobacterium shows attachment to the PAH substrate source, which is considered to be a particular adaptation to low bioavailability as it results into increased substrate flux to the degraders. To examine whether PAH-degrading Mycobacterium in real PAH-contaminated soils, in analogy with model systems, are preferentially associated with PAH-enriched soil particles, the distribution of PAHs, of the PAH-mineralizing capacity and of Mycobacterium over different fractions of a soil with an aged PAH contamination was investigated. The clay fraction contained the majority of the PAHs and showed immediate pyrene- and phenanthrene-mineralizing activity upon addition of (14)C-labelled pyrene or phenanthrene. In contrast, the sand and silt fractions showed a lag time of 15-26 h for phenanthrene and 3-6 days for pyrene mineralization. The maximum pyrene and phenanthrene mineralization rates of the clay fraction expressed per gram fraction were three to six times higher than those of the sand and silt fractions. Most-probable-number (MPN)-polymerase chain reaction demonstrated that Mycobacterium represented about 10% of the eubacteria in the clay fraction, while this was only about 0.1% in the sand and silt fractions, indicating accumulation of Mycobacterium in the PAH-enriched clay fraction. The Mycobacterium community composition in the clay fraction represented all dominant Mycobacterium populations of the bulk soil and included especially species related to Mycobacterium pyrenivorans, which was also recovered as one of the dominant species in the eubacterial communities of the bulk soil and the clay fraction. Moreover, Mycobacterium could be identified among the major culturable PAH-degrading populations in both the bulk soil and the clay fraction. The results demonstrate that PAH-degrading mycobacteria are mainly associated with the PAH-enriched clay fraction of the examined PAH-contaminated soil and hence, that also in the environmental setting of a PAH-contaminated soil, Mycobacterium might experience advantages connected to substrate source attachment.
摘要 分枝杆菌常作为多环芳烃（PAH）的降解菌从受PAH污染的土壤中分离出来。在模型系统中，分枝杆菌表现出附着于PAH底物源，这被认为是对低生物可利用性的一种特殊适应，因为它会导致更多底物流向降解菌。为了研究在实际受PAH污染的土壤中，与模型系统类似，PAH降解分枝杆菌是否优先与富含PAH的土壤颗粒相关联，我们调查了一个受PAH长期污染土壤不同组分中PAH的分布、PAH矿化能力以及分枝杆菌的分布情况。黏粒组分含有大部分PAH，添加（14）C标记的芘或菲后，立即表现出芘和菲的矿化活性。相比之下，砂粒和粉粒组分在菲矿化方面有15 - 26小时的延迟，芘矿化则有3 - 6天的延迟。以每克组分表示，黏粒组分的芘和菲最大矿化速率比砂粒和粉粒组分高3至6倍。最可能数（MPN）-聚合酶链反应表明，分枝杆菌在黏粒组分中约占真细菌的10%，而在砂粒和粉粒组分中仅约为0.1%，这表明分枝杆菌在富含PAH的黏粒组分中积累。黏粒组分中的分枝杆菌群落组成代表了整个土壤中所有优势分枝杆菌种群，尤其包括与食芘分枝杆菌相关的物种，该物种在整个土壤和黏粒组分的真细菌群落中也是优势物种之一。此外，在整个土壤和黏粒组分中主要可培养的PAH降解菌群中都能鉴定出分枝杆菌。结果表明，PAH降解分枝杆菌主要与所检测的受PAH污染土壤中富含PAH的黏粒组分相关联，因此，在受PAH污染土壤的环境中，分枝杆菌也可能因附着于底物源而具有优势。
