which of the following is not a symboitic nitrogen fixing bacterium\tclostridium\tphizobium leguminosarum\tfrankia\tmycobacterium

The correct option is 1.
Clostridium is a genus of Gram-positive bacteria, belonging to the Firmicutes. They are obligate anaerobes capable of producing endospores. Individual cells are rod-shaped, which gives them their name, from the Greek kloster or spindle. These characteristics traditionally defined the genus; however many species originally classified as Clostridium have been reclassified in other genera.