What does MPN stand for in microbiological analysis?

In microbiological analysis, MPN stands for Most Probable Number. This statistical method is utilized to estimate the concentration of viable microorganisms in a sample, especially when dealing with samples where the organisms might not grow on solid media or are present in very low numbers.

The MPN method involves a series of dilutions and subsequent inoculation into a suitable growth medium. After incubation, the presence or absence of growth in each dilution is observed, and statistical tables are then used to determine the most probable number of organisms in the original sample based on the pattern of growth observed. This method is particularly valuable in wastewater analysis, as it allows for the estimation of fecal coliforms or other bacterial populations that might be indicators of contamination or pollution levels.

Other options do not accurately reflect the terminology used in microbiology or the context in which microbial populations are quantified, which further underscores why "Most Probable Number" is the correct definition for MPN.