Carboxyl groups have an electronegative oxygen atom double bonded to a carbon atom. This carbon-oxygen bond is very polar and the fact that its a double bond increases the polarity of the bond.
PEA agar, also referred to as Phenylethyl Alcohol Agar is a medium  used by microbiologists to grow microorganisms. The ingredient that  supplies nitrogen is casein. Making the world better, one answer at a time.
The primary way. nitrogen is supplied to plants is through the. mineralization of organic material in the soil. However, nitrogen fixation by bacteria. such as Rhizobium spp. and Cyanobacteria spp. is almost as important as mineralization, and is a primary source of nitrogen.