Department of Molecular and Cell Biology, Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, Scotland, UK.
FEMS Microbiol Ecol. 2003 May 1;44(1):67-78. doi: 10.1016/S0168-6496(02)00453-1.
Abstract Quantitative models of bacterial conjugation are useful tools in environmental risk assessment and in studies of the ecology and evolution of bacterial communities. We constructed a mathematical model for gene transfer between bacteria growing on a solid surface. The model considers that donor and recipient cells will form separate colonies, which grow exponentially until nutrient exhaustion. Conjugation occurs when donor and recipient colonies meet, all recipient cells becoming transconjugants instantly, after which they act as donors. The model was tested theoretically by computer simulations that followed the histories of individual bacterial colonies and was validated for initial surface coverage of 60% or less, where confluent growth does not occur. Model predictions of final number of donors, recipients and transconjugants were tested experimentally using a filter mating system with two isogenic strains of Pseudomonas fluorescens MON787 acting as donor and recipient of plasmid RP4. Experimental trends resulting from varying donor and recipient inoculum numbers and donor:recipient ratios were well described by the model, although it often overestimated conjugation by 0.5-2 orders of magnitude. Predictions were greatly improved, generally to within half a log unit of experimental values, by consideration of the time for conjugative transfer. The model demonstrates the relationship between spatial separation of cells and nutrient availability on numbers of transconjugants. By providing a mechanistic approach to the study conjugation on surfaces, the model may contribute to the study of gene transfer in natural environments.
摘要 细菌接合的定量模型是环境风险评估以及研究细菌群落的生态学和进化的有用工具。我们构建了一个用于在固体表面上生长的细菌之间基因转移的数学模型。该模型考虑到供体和受体细胞将形成单独的菌落，这些菌落将在营养物质耗尽之前呈指数增长。当供体和受体菌落相遇时，就会发生接合，所有受体细胞立即成为转导子，然后它们充当供体。该模型通过模拟单个细菌菌落的历史进行了理论测试，并在初始表面覆盖率为 60%或更低的情况下进行了验证，因为此时不会发生融合生长。使用带有两个同基因荧光假单胞菌 MON787 菌株作为供体和受体的滤膜交配系统，通过实验测试了模型对最终供体、受体和转导子数量的预测。实验结果表明，模型可以很好地描述接种体数量和供体：受体比例变化的趋势，尽管它经常高估了接合作用 0.5-2 个数量级。通过考虑共轭转移的时间，预测得到了很大的改善，通常可以将实验值提高到半对数单位以内。该模型展示了细胞的空间分离和营养物质可用性对转导子数量的关系。通过为表面上的接合研究提供一种机械方法，该模型可能有助于研究自然环境中的基因转移。
