the Actinobacteria,. [ 1 ] The Firmicutes contain the well-known genera that are majority of Gram-positives of medical interest: Staphylococcus , Streptococcus , Enterococcus (cocci), Bacillus , Clostridium and Listeria (bacilli/rods). This group also been expanded to include the Mycoplasma , or Mollicutes, bacteria-like organisms that lack cell walls and cannot