<prompt> The major constituents in agar areFatsAminoacidsPolysaccharidesPolypeptides  <response>: Agar, a polysaccharide extract of a marine alga, is uniquely suitable for microbial cultivation because it is resistant to microbial action and becauseit dissolves at 100degC but does not gel until cooled below 45degC; cells can be suspended in the medium at 45degC and the medium quickly cooled to a gel without harming them.Ref: Jawetz, Melnick, Adelbergs Medical Microbiology; Twenty-Seventh Edition; Chapter 5; Cultivation of Microorganisms 