Actinomycetes are a group of bacteria that live mainly in the soil. Clusters of actinomycetes form long, thin filaments in the soil, and have an important role in the environmental carbon cycle. A hardy group of bacteria, they are particularly adept at surviving harsh conditions and breaking down tough substances in the soil, returning their components back down to the most basic structures.
Found both in and on the soil, actinomycetes grow in a way similar to fungi. They reproduce via spores, which are round bodies that develop a single strand. From this strand the bacterial body begins to first curl at the tip, and then to divide into segments within the strand. The walls of the strand thicken as the partitions divide, and once these partitions mature the strand is ready to produce more spores to continue the division.
When dirt and soil are freshly dug, they release a distinct, earthy smell. Most bacteria in the dirt break substances down to their base compounds, but actinomycetes are responsible for the decomposition of some of the toughest of these substances. Cellulose is found in the walls of plant cells, and chitin serves a similar purpose in the cell walls of fungi. There aren't many bacteria that can break down these difficult substances, but actinomycetes are able to under even the harshest of conditions.
The actinomycetes are particularly important in areas where there is a lot of decaying plant matter, such as forests and grasslands. Without their ability to participate in the decay of plant and fungi, nutrients from these dead organisms would not be restored to the soil for living plants to absorb and use. Activated by high pH levels, a change in the soil's nutrient levels can deactivate the recycling processes of these organisms and drastically impact the soil ecosystem. When the soil contains a low pH level, not only are actinomycetes inactive but other soil decomposers, fungi, is activated. With this shift, soil conditions change and can become favorable for a new set of plants, such as unwanted weeds and invasive species.
It is not uncommon for colonies of these bacteria to grow around certain plants, particularly species like the cliffrose and bitterbrush. The plant and the bacteria can form a symbiotic relationship, where the actinomycetes feed on the decaying parts of the plant and convert nitrogen back into a form that is usable by the plant.