Rhodococcus is a genus of aerobic, nonsporulating, nonmotile Gram-positive bacteria, a few species are pathogenic, most are benign, and have been found to thrive in a broad range of environments, including soil, water, and eukaryotic cells. Some species have large genomes, including the 9.7 megabasepair genome (67% G/C) of Rhodococcus sp. RHA1. Rhodococcus are important owing to their ability to catabolize a wide range of compounds and produce bioactive steroids, acrylamide, and acrylic acid, and their involvement in fossil fuel biodesulfurization. Another important application of Rhodococcus comes from bioconversion, using biological systems to convert cheap starting material into more valuable compounds, such as its ability to metabolize harmful environmental pollutants, including toluene, naphthalene, herbicides, and PCBs. Rhodococcus pneumonia is a zoonotic infection that causes a nodular histiocytic and cavitary pneumonia in immunosuppressed patients, most commonly with HIV/AIDS.