What effect does bacteria have on a urine sample left at room temperature?

The presence of bacteria in a urine sample left at room temperature can lead to cell breakdown due to the metabolic activities of the bacteria. When bacteria are present, they can consume nutrients and produce waste products, which may harm or disrupt the cells in the urine sample. This breakdown can result in the lysis (or breakdown) of red and white blood cells, as well as epithelial cells that may be present in the sample.

Furthermore, as bacteria multiply, they alter the composition of the urine, potentially affecting factors such as pH and the concentration of various substances. This can contribute to the overall deterioration of the sample's integrity, making it less useful for accurate diagnostic purposes.

In contrast, other options—such as decreasing sample volume, inhibiting crystal formation, or enhancing urine color—do not accurately represent the typical consequences of bacterial contamination in a urine sample. The most significant and immediate effect is the breakdown of cells, making the identified answer a suitable choice for understanding how bacteria impact urine samples.