An alternative approach to the yeast extract-nalidixic acid method for determining the proportion of metabolically active aquatic bacteria

When metabolizing aquatic bacteria were determined by the conventional approach to the yeast extract‐nalidixic acid method the apparent percentage of viable bacteria depended on the critical length beyond which cells were scored as viable. An alternative approach allowed the identification of an optimum critical length and the fixing of a lower limit to the true percentage of viable bacteria.