A type of bacteria colonizes on the surface of a leaf, where it obtains nutrition from the leaf's nonliving, waxy covering without harming the plant, and inhibits the growth of other microbes that are plant pathogens. If this bacteria gains access to the inside of a leaf, however, it causes a fatal disease in the plant. Once the plant dies, the bacterium and its offspring decompose the plant. What is the correct sequence of ecological roles played by the bacterium in the situation described here