Which one of the following  bacteria is  cell  wall  deficient?
Mycoplasma: 

This is a naturally occurring bacteria without cell walls. 
Mycoplasma is classiﬁed as an independent bacterial genus. 
They don't require a hypertonic environment for maintenance and are stable in culture medium.
Escherichia  coli
Salmonella  typhi
Mycoplasma
Treponema pallidum