Discovery

Sometimes, figuring something out only deepens the overall mystery.

Take Pseudomonas fluorescens D7, for example.

Ann Kennedy, a USDA-Agricultural Research Service soil microbiologist at Washington State University, has isolated the native bacteria as a perfectly natural way to fight cheatgrass, also known as downy brome, scientific name Bromus tectorum. Recently, she and her colleagues were awarded a large grant to test the effectiveness of Pseudomonas fluorescens D7 on cheatgrass in rangeland.

Cheatgrass, which was introduced in the late 19th century as a forage crop, is an aggressive invader, a grass that has, according to botanist Washington State University Richard Mack, changed the ecology, if not the landscape, of much of the western United States. Cheatgrass crowds out other plants and changes the fire ecology of a region. Because it matures in early spring, it dries out and provides a hot-burning fuel for wildfires, to which its seeds are impervious.

The reason invasive species are so successful is they are out of context, out of their normal environment. Not all introduced plants are necessarily invasive. They may grow in a foreign environment, but not sufficiently well to crowd out native species. But if a plant does well in an environment and lacks native predators or enemies, then it can become aggressively invasive. Other very visible invasives in the Pacific Northwest are Scotch Broom and purple loosestrife. The reason they are so visible is they have no natural controls.

So it is with cheatgrass. Originally from Eastern Europe, it is not the problem there that it is here. In its native environment, it has no advantage over competitors and predators.

Kennedy and her colleagues imported soil from Turkey and Kazakhstan and found that 90 percent of the organisms in it were inhibitory to cheatgrass. Only 50 percent of organisms in domestic soil are inhibitory. (more…)