Question

which bacteria is used to determine the level of water pollution

Answer 1

Disease-causing microorganisms are referred to as pathogens. Although the vast majority of bacteria are either harmless or beneficial, a few pathogenic bacteria can cause disease. Coliform bacteria, which are not an actual cause of disease, are commonly used as a bacterial indicator of water pollution. Other microorganisms sometimes found in contaminated surface waters that have caused human health problems include:

Burkholderia pseudomallei
Cryptosporidium parvum
Giardia lamblia
SalmonellaNorovirus and
other virusesParasitic worms including the Schistosoma type.

Coliform bacteria, which are not an actual cause of disease, are commonly used as a bacterial indicator of water pollution. 

Answer 2

i think Cynobacteria.......