Genetic Exchange Within and Between Species of Bacteria

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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.