What is the typical dilution series used in the multiple-tube fermentation test?

The typical dilution series used in the multiple-tube fermentation test is indeed 10 mL, 1 mL, and 0.1 mL. This specific series allows for a range of concentrations that can effectively capture the presence of coliform bacteria in a water sample.

Using these particular dilution factors is significant because it creates a gradient that enhances the likelihood of detecting coliforms. Starting with 10 mL provides a larger sample volume, which may contain higher concentrations of bacteria, while the smaller volumes of 1 mL and 0.1 mL enable the detection of lower concentrations. This systematic approach helps to ensure that a wide range of bacterial populations can be identified, contributing to a more comprehensive understanding of water quality. Each dilution plays a crucial role in estimating the total number of bacteria present based on the growth observed in the fermentation test.

The other options involve different volume dilutions, which might not be as effective in capturing the required range for a proper analysis in typical laboratory settings, thus making them less suitable for this type of test.