Ammonium Mineral Salts Medium (AMS). Another common medium used for methanotrophic growth is “Ammonium Mineral Salts” medium (AMS) in which 0.5 g NH4Cl is substituted for the 1 g of KNO3 (Whittenbury et al., 1970). This medium is less common in practice than NMS, as some methanotrophs do not grow well with ammonium as a nitrogen source. The rest of the recipe and steps of preparation are identical to NMS medium.