Fundamentals of Microbiology

Principle

Bacteria-tight membrane filters capable of retaining microorganisms larger than 0.45 micrometer ( m m) or 0.22 m m can be used fir sterilization of water and heat-labile solutions. These filters are also frequently used for quantitative analysis of water. This method offers several advantages over the conventional multiple-tube (MPN) method of water analysis: 1. Results are available in a shorter period of time 2. Larger volume of sample can be processed 3. The method is more accurate and results are reproducible. Disadvantage of this method is that if the water or solution is highly turbid with large quantities of suspended materials, the pores of the filter get clogged which restrict the flow of the specific volume of water / solution.