Genetic Exchange Within and Between Species of Bacteria

这些研究解决了有关芽孢杆菌属自然种群中自由活的土壤细菌的基因的基本问题。问题包括：自然界中存在的遗传变异性的数量；细菌细胞之间的基因交换是否常见；以及野生细菌种群是否几乎完全由独立繁殖的克隆组成，不同克隆的细胞之间没有横向的基因交换。许多细菌在不同的细菌细胞之间交换基因，这种交换过程类似于人们熟悉的动植物有性繁殖。细菌有几种不同的“性行为”机制，其中一种称为“转化”。当一种类型的细胞的DNA穿过环境，被另一种细胞拾取并插入到受体细胞的DNA中时，就会发生转化。因此，发生了基因交换，受体细胞获得了新的生物学特性。例如，受体细胞可能获得一种基因，使其能够从环境中的新来源获得能量，或者它可能获得一种基因，使其对邻近不同类型的细菌或真菌产生的天然抗生素产生抗药性。影响自然界中成百上千种细菌功能的交换是可能的。了解细菌种群的遗传变异性和遗传重组的数量将有助于预测这些种群在其环境中变化的能力。细菌自然种群中的基因交换既有有益的影响，也有有害的影响。使土壤细菌种群适应不断变化的农业条件的基因可以传播并更好地使这些有益生物适应它们在养分向植物转移中的作用。然而，导致植物病害的基因也可能传播。动物和人类的自然致病基因，例如由芽孢杆菌产生的炭疽病，可能会在野生细菌种群中传播。因此，完全了解基因如何以及何时在细菌种群中移动是很重要的。

Basic questions concerning genes in natural populations of free.living soil bacteria in the genus >Bacillus> are addressed by these studies. Questions include: the amount of genetic variability present in nature; whether the exchange of genes between bacterial cells is common; and whether wild bacterial populations consist almost entirely of independently multiplying clones, with no lateral exchange of genes between cells of different clones. Many bacteria exchange genes between different bacterial cells, processes of exchange akin to the familiar sort of sexual reproduction of animals and plants. Several different mechanisms of "sexuality" are known for bacteria; one is known as "transformation". Transformation occurs when the DNA of one type of cell passes through the environment and is picked up by another cell and inserted into the recipient cell's DNA. Thus a genetic exchange occurs and the recipient cell acquires new biological properties. For example, the recipient cell may acquire a gene which allows it to obtain energy from a new source in its environment, or it may acquire a gene which makes it resistant to a natural antibiotic produced by a neighboring and different type of bacteria or a fungus. Exchanges which influence hundreds or thousands of bacterial functions in nature are possible. An understanding of the genetic variability and amounts of genetic recombination of bacterial populations will allow prediction of the abilities of these populations to change in their environments. The exchange of genes in natural populations of bacteria can have both beneficial and harmful effects. Genes which adapt soil bacterial populations to changing agricultural conditions can spread and better adapt these beneficial organisms to their role in the movement of nutrients to plants. However, genes which cause plant diseases could also be spread. Naturally pathogenic genes for animals and humans, for example anthrax disease which is produced by >Bacillus>, could conceivably move around in wild bacterial populations. Thus it is important to understand completely how and when genes move around in bacterial populations.