UFZ, Helmholtz Centre for Environmental Research, Department of Environmental Microbiology, 04318 Leipzig, Germany.
Environ Sci Technol. 2010 Dec 15;44(24):9304-10. doi: 10.1021/es100776h. Epub 2010 Nov 16.
The role of bacterial growth and translocation for the bioremediation of organic contaminants in the vadose zone is poorly understood. Whereas air-filled pores restrict the mobility of bacteria, diffusion of volatile organic compounds in air is more efficient than in water. Past research, however, has focused on chemotactic swimming of bacteria along gradients of water-dissolved chemicals. In this study we tested if and to what extent Pseudomonas putida PpG7 (NAH7) chemotactically reacts to vapor-phase gradients forming above their swimming medium by the volatilization from a spot source of solid naphthalene. The development of an aqueous naphthalene gradient by air-water partitioning was largely suppressed by means of activated carbon in the agar. Surprisingly, strain PpG7 was repelled by vapor-phase naphthalene although the steady state gaseous concentrations were 50-100 times lower than the aqueous concentrations that result in positive chemotaxis of the same strain. It is thus assumed that the efficient gas-phase diffusion resulting in a steady, and possibly toxic, naphthalene flux to the cells controlled the chemotactic reaction rather than the concentration to which the cells were exposed. To our knowledge this is the first demonstration of apparent chemotactic behavior of bacteria in response to vapor-phase effector gradients.
细菌的生长和转移在包气带中有机污染物生物修复中的作用还知之甚少。虽然充满空气的孔隙限制了细菌的迁移能力，但挥发性有机化合物在空气中的扩散效率要高于在水中。然而，过去的研究主要集中在细菌沿着水溶解化学物质梯度的趋化游动上。在这项研究中，我们测试了 Pseudomonas putida PpG7（NAH7）是否以及在何种程度上对其游泳介质上方由固体萘的点源挥发形成的蒸气相梯度产生趋化反应。通过在琼脂中使用活性炭，极大地抑制了萘通过气-水分配形成的水相萘梯度。令人惊讶的是，尽管稳定状态下的气态浓度比导致同一菌株正向趋化的水相浓度低 50-100 倍，但菌株 PpG7 还是被蒸气相萘所排斥。因此，人们认为，导致稳定且可能有毒的萘通量流向细胞的有效气相扩散控制了趋化反应，而不是细胞暴露的浓度。据我们所知，这是首次证明细菌对蒸气相效应物梯度表现出明显的趋化行为。
