Collaborative Research: Horizontal Gene Transfer in Porous Media: Experiments and Modeling

细菌可以将DNA从一个细胞转移到另一个细胞，即使它们是远亲。这被称为水平基因转移，它可以帮助细菌适应新的污染物和环境条件。它还促进了抗生素耐药性等性状的传播。在土壤中，当细菌接触被吸附在土壤表面的DNA时，一种水平基因转移机制就会发生。土壤表面为DNA提供了吸收的场所，这样它们就可以与地下水输送的微生物细胞相互作用/“感染”。了解这一过程很重要，因为它有助于阳性（降解污染物）和阴性（抗生素耐药性）细菌特性的发展和传播。细胞运动或运动影响细胞与表面联系的频率，因此可能影响细胞与吸附DNA之间相互作用的频率。本项目研究了细胞运动、细胞附着和运输以及DNA吸附到土壤中的基因转移之间的关系。这项研究的目标是确定是什么控制着细菌的转化速度；这取决于它们在月球表面停留的时间。细胞只有当它们真正粘在土壤表面时才会发生转化，而不是当它们被困在土壤表面附近时。因此，运动细胞和非运动细胞的转化率将取决于它们在涂有DNA的表面上停留的时间。运动细胞游动的能力使它们能够独立于表面相互作用的化学反应接近表面。因此，运动细胞比非运动细胞表现出更高的转化频率。这些假设将通过具体的实验和建模目标进行测试，包括确定径向驻点流（RSPF）系统中的附着机制，微模型系统中的停留时间分布和空间分布，以及批和柱系统中的附着-分离和基因转移动力学。实验将涉及可运动和不可运动的细菌菌株，并将使用涂有DNA的表面。研究结果将用于开发和测试土壤环境中细菌运输和水平基因转移的模型。由于地下水是饮用水和灌溉用水的主要来源，其易受生物和化学污染物的影响是一个重大的公共卫生问题。研究结果将微生物迁移和微生物演化的相关过程结合起来，为地下水污染风险评价提供参考。参与这项计划的研究生和本科生将接受跨学科的教育，包括外展的经验。研究人员将继续致力于招募女性和少数族裔，并通过伊利诺伊大学和加州大学戴维斯分校的无国界工程师组织（EWB）和加州大学戴维斯分校的妇女工程联系培训本科生。

Bacteria can transfer DNA from one cell to another, even if they are distantly related. This is called horizontal gene transfer, and it helps bacteria adapt to new contaminants and environmental conditions. It also facilitates the spread of traits such as antibiotic resistance. In the soil, one mechanism of horizontal gene transfer can occur when bacteria contact DNA adsorbed to soil surfaces. Soil surfaces provide places for the DNA to sorb so that they can interact/"infect" with groundwater transported microbial cells. It is important to understand this process because it contributes to the development and spread of both positive (degrading contaminants) and negative (antibiotic resistance) bacterial traits. Cell movement, or motility, affects how often cells associate with surfaces, and therefore is likely to affect the frequency of interaction between the cells and adsorbed DNA. This project investigates the relationships among cell motility, cell attachment and transport, and gene transfer by DNA adsorbed to soil. The research goal is to identify what controls how fast bacteria are transformed; this is expected to depend on how long they reside on the surface. Cells are expected to transform only when they are actually stuck on the soil surface, not when they are trapped near, but not on, soil surfaces. Thus transformation rates of both motile and non-motile cells will depend on their residence-time on surfaces coated with DNA. The ability of motile cells to swim allows them to approach surfaces independent of the chemistry of surface interactions. Consequently motile cells should exhibit greater frequency of transformation than non-motile cells. These hypotheses will be tested through specific experimental and modeling objectives involving determination of attachment mechanisms in a radial stagnation point flow (RSPF) system, of residence time distributions and spatial distribution in a micromodel system, and of attachment-detachment and gene transfer kinetics in batch and column systems. The experiments will involve both motile and non-motile bacterial strains and will use surfaces coated with DNA. Results will be used in the development and testing of models of bacterial transport and horizontal gene transfer in the soil environment.As groundwater is a major source of drinking water and irrigation water, its vulnerability to biological and chemical contaminants is a major public health concern. The research results will help risk assessment of groundwater contamination, as related processes of microbial transport and microbial evolution are studied together. Graduate and undergraduate students participating in this proposed project will receive an interdisciplinary education, including experience in outreach. The investigators will continue their commitment to recruit women and minorities and to train undergraduate students through Engineers without Borders (EWB) at U of I and at UC Davis and Women Engineering Link at UC Davis.