Which among the following are the smallest living cells, known  without  a definite cell wall, pathogenic to plants as well as animals and can survive without oxygen?

Mycoplasma are pathogenic to plants, animals and man. These are the smallest living cells that do not have cell wall and can survive without oxygen. 

(1) Pseudomonas is a eubacterium and has a cell wall. 

(2) Nostoc is a fi lamentous cyanobacterium with heterocysts and it fi xes atmospheric nitrogen. 

(3) Bacillus is a eubacterium and it has cell wall.