What is the purpose of adding sodium thiosulfate to a microbiological sample bottle?

Adding sodium thiosulfate to a microbiological sample bottle serves the important purpose of removing chlorine residual that may be present in the water sample. Chlorine is commonly used as a disinfectant in water treatment processes, but it can be harmful to microbial analysis since it can kill or inhibit the growth of bacteria, thus compromising the results of microbiological testing. By neutralizing chlorine, sodium thiosulfate ensures that any microorganisms within the sample can survive and multiply, providing accurate and reliable analysis of microbial content.

The other options, while they may relate to different processes in water treatment or microbiological analysis, do not accurately describe the main function of sodium thiosulfate in this context. Enhancing microbial growth would not be relevant as the purpose here is to ensure the presence of existing microbes without interference from chlorine. Stabilizing pH is not a direct role of sodium thiosulfate, although the pH of a sample can affect microbial growth. Reducing sedimentation is unrelated to the effects of sodium thiosulfate, as it primarily acts on chlorine rather than physical characteristics of the sample.