Tired of coming home and seeing those ugly black streaks all over your roof? Those streaks are a build up of bacteria known as gloeocapsa magma. They feed off of the limestone filler in the shingles.  If allowed to live on your roof long enough, it will also create a fungus known as lichen.  Another well known organism growing on your roof is moss.  It is an actual plant that retains moisture shortining the life of your roof.