Mycoplasma are a mollicute genus of bacteria that lack a cell wall around their cell membranes. This characteristic makes them naturally resistant to many common antibiotics such as penicillin or other beta-lactam antibiotics that target cell wall synthesis. P37, a protein encoded for by M. hyorhinis, has been found to promote the invasiveness of prostate cancer cells. P37 also causes the growth, morphology, and the gene expression of the cells to change, causing them to become a more aggressive phenotype.