What is the difference between more than one ATCC No. for the same microorganism?

Microbiology
1

1- What is the difference between E.coli ATCC 8739 and E.coli ATCC 25922 ?

2- Why some of Microorganism has many ATCC No.? and what is the difference ?

2

Different ATCC number of same organisms are the different strains of the same organisms.