Sikorski Johannes, Graupner Stefan, Lorenz Michael G, Wackernagel Wilfried
Genetik, Fachbereich Biologie, Carl von Ossietzky Universität Oldenburg, Postfach 2503, D-26111 Oldenburg, Germany.
Microbiology (Reading). 1998 Feb;144 ( Pt 2):569-576. doi: 10.1099/00221287-144-2-569.
Natural transformation of the soil bacterium Pseudomonas stutzeri JM300 in a non-sterile brown earth microcosm was studied. For this purpose, the microcosm was loaded with purified DNA (plasmid or chromosomal DNA, both containing a high-frequency-transformation marker, his+, of the P. stutzeri genome), the non-adsorbed DNA was washed out with soil extract and then the soil was charged with competent cells (his-1). Both chromosomal and plasmid transformants were found among the P. stutzeri cells recovered from the soil. The number of plasmid transformants increased in a linear fashion with the amount of DNA added [10-600 ng (0.7 g soil)-1]. The observed efficiency of transformation, the time course of transformant formation and the complete inhibition of transformation by DNase I, when added to the soil, were similar to that seen in optimized transformations in nutrient broth. Addition of cells as late as 3 d after loading the soil with plasmid DNA still yielded 3% of the initial transforming activity. This suggests that nucleases indigenous to the soil destroyed the transforming DNA, but at a rate allowing considerable DNA persistence. Transformants were also obtained when intact P. stutzeri cells were introduced into the soil to serve as plasmid DNA donors. Apparently, DNA was released from the cells, adsorbed to the soil material and subsequently taken up by recipient cells. The results indicate that competent cells of P. stutzeri were able to find access to and take up DNA bound on soil particles in the presence of micro-organisms and DNases indigenous to the soil.
研究了土壤细菌斯氏假单胞菌JM300在非无菌棕壤微观世界中的自然转化。为此，向微观世界中加入纯化的DNA（质粒或染色体DNA，两者均含有斯氏假单胞菌基因组的高频转化标记his⁺），用土壤提取物洗去未吸附的DNA，然后向土壤中加入感受态细胞（his⁻1）。从土壤中回收的斯氏假单胞菌细胞中发现了染色体和质粒转化体。质粒转化体的数量随添加的DNA量呈线性增加[10 - 600 ng（0.7 g土壤）⁻¹]。观察到的转化效率、转化体形成的时间进程以及向土壤中添加DNase I后对转化的完全抑制，与在营养肉汤中优化转化时所见相似。在向土壤中加入质粒DNA 3天后才添加细胞，仍能产生初始转化活性的3%。这表明土壤中的核酸酶会破坏转化DNA，但速率允许相当数量的DNA持续存在。当将完整的斯氏假单胞菌细胞引入土壤作为质粒DNA供体时，也获得了转化体。显然，DNA从细胞中释放出来，吸附到土壤物质上，随后被受体细胞吸收。结果表明，在存在土壤微生物和核酸酶的情况下，斯氏假单胞菌的感受态细胞能够找到并摄取结合在土壤颗粒上的DNA。
