Why is a water sample for bacteriological analysis packed in ice if it cannot be analyzed immediately?

When a water sample for bacteriological analysis cannot be processed immediately, it is crucial to preserve its integrity to ensure accurate results. Packing the sample in ice serves to retard changes in the number of bacteria present in the water.

By cooling the sample, the metabolic activities of bacteria are slowed down. This helps to minimize the growth of existing bacteria as well as the potential introduction of new bacteria between the time of collection and the time of analysis. In warm conditions, bacteria can proliferate rapidly, leading to an oversampling of bacterial counts that do not accurately reflect the true state of the water at the time of collection. Therefore, the cooling effect of ice effectively preserves the sample as close as possible to its original condition, ensuring the analysis will yield reliable data regarding the water's bacteriological quality.