[[1]] bacteria is resistant to penicillin.
 

Concept: Mycoplasma is 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. 
They can be parasitic or saprotrophic.
Hence,  Mycoplasmais the correct option.