Robert Koch assistant advised him to use agar instead of gelatine for solidifying culture media for cultivation of bacteria as -: (A) Agar has more nutrition, (B) Gelatin melts at 37°C, (C) Gelatin is not easily available, (D) Agar is cheaper
Answer is B. Agar is preferred to gelatin as a solidifying agent in culture media.
This is because gelatin melts at relatively low temperature (<35o C), while agar melts at around 85° C.
Therefore, when gelatin is incubated at the normal temperature for bacterial growth, i e. at 37° C, it melts, while agar remains solid.