Department of Biological Sciences, Initiative for Bioinformatics and Evolutionary Studies, University of Idaho, P.O. Box 443051, Moscow, ID 83844-3051, USA.
Appl Environ Microbiol. 2011 Aug;77(15):5079-88. doi: 10.1128/AEM.00090-11. Epub 2011 Jun 3.
Although biofilms represent a common bacterial lifestyle in clinically and environmentally important habitats, there is scant information on the extent of gene transfer in these spatially structured populations. The objective of this study was to gain insight into factors that affect transfer of the promiscuous multidrug resistance plasmid pB10 in Escherichia coli biofilms. Biofilms were grown in different experimental settings, and plasmid transfer was monitored using laser scanning confocal microscopy and plate counting. In closed flow cells, plasmid transfer in surface-attached submerged biofilms was negligible. In contrast, a high plasmid transfer efficiency was observed in a biofilm floating at the air-liquid interface in an open flow cell with low flow rates. A vertical flow cell and a batch culture biofilm reactor were then used to detect plasmid transfer at different depths away from the air-liquid interface. Extensive plasmid transfer occurred only in a narrow zone near that interface. The much lower transfer frequencies in the lower zones coincided with rapidly decreasing oxygen concentrations. However, when an E. coli csrA mutant was used as the recipient, a thick biofilm was obtained at all depths, and plasmid transfer occurred at similar frequencies throughout. These results and data from separate aerobic and anaerobic matings suggest that oxygen can affect IncP-1 plasmid transfer efficiency, not only directly but also indirectly, through influencing population densities and therefore colocalization of donors and recipients. In conclusion, the air-liquid interface can be a hot spot for plasmid-mediated gene transfer due to high densities of juxtaposed donor and recipient cells.
尽管生物膜代表了临床和环境中重要栖息地中常见的细菌生活方式，但关于这些空间结构群体中基因转移程度的信息却很少。本研究的目的是深入了解影响大肠杆菌生物膜中易位多药耐药质粒 pB10 的因素。在不同的实验条件下培养生物膜，并使用激光扫描共聚焦显微镜和平板计数监测质粒转移。在封闭的流动池中，表面附着的淹没生物膜中的质粒转移可以忽略不计。相比之下，在低流速的开放流动池中，在气液界面处漂浮的生物膜中观察到高质粒转移效率。然后使用垂直流动池和分批培养生物膜反应器来检测不同深度远离气液界面处的质粒转移。只有在靠近界面的狭窄区域才会发生广泛的质粒转移。下部区域的转移频率要低得多，这与氧气浓度的迅速下降相对应。然而，当使用 E. coli csrA 突变体作为受体时，在所有深度都获得了厚厚的生物膜，并且在整个过程中以相似的频率发生质粒转移。这些结果以及来自单独的需氧和厌氧交配的数据表明，氧气可以通过影响种群密度并因此使供体和受体细胞相邻来直接和间接地影响 IncP-1 质粒转移效率。总之，由于毗邻供体和受体细胞的高密度，气液界面可能成为质粒介导基因转移的热点。
