INCREASING THE EFFICIENCY OF THE PLATE COUNTING METHOD FOR ESTIMATINGBACTERIAL DIVERSITY

A set of 25 different media, selected for their ability to support the growth of a large number of bacteria, yielded between four to seven t imes more morphologically distinct bacteria from ryegrass and alfalfa roots and soil samples when used for plate counting than a single medi um. The 25 media in the selection included some of the commonly used m edia supplemented with antibiotics or toxicants and media containing o nly a single nutrient. Media used singly included King's B, Luria-Bert ani, Nutrient Agar, Tryptic Soy Agar, and Cold-extracted Soil Extract Agar. Based on the results of this study we recommend the use of a set of different media, as opposed to one or two media, in order to incre ase the efficiency of plate counting method for estimating bacterial d iversity. (C) 1997 Elsevier Science B.V.