Bacteria Population constitute how much . . . . . . . . % of Organic matter.

The bacterial population constitutes 2 - 4% of organic matter.
Soil organic matter is the organic component of soil, consisting of three primary parts including small and fresh plant residues, small living soil microorganisms, decomposing active organic matter and stable organic matter.
Soil organic matter is the primary source of carbon which gives energy and nutrients to soil organisms.