MPN Drop Agar Method for Determination of Heterotrophic Microorganisms in Soil and Water Samples Using Tissue Plate as a Carrier

Abstract

The most probable number (MPN) method is a culture-based method commonly used in the field of environmental microbiology to examine microbial populations in liquid substrates. The MPN tests require a wide range of special laboratory equipment, a lot of laboratory space, and skilled staff, which together limit their applicability. This paper presents a modified MPN method, which reduces the experimental requirements by applying tissue plate as a carrier. The modified MPN method introduces a fast-filled tissue plate with 5 × 5 squares as agar carrier, instead of the commonly used set of glass tubes. Further, self-refilling automatic syringe Socorex® was implemented to apply samples to the plate. The response of the modified MPN method was tested on eight selected bacterial strains as well as on soil and water samples. Simultaneously, all the strains and samples were tested by standard spread plate method. High linear correlation between the two methods was found, which makes a new modified MPN method a useful alternative within the field of environmental microbiology.