What basis does the API test use to differentiate between bacterial species?

The API test differentiates between bacterial species based on their metabolic activities. This biochemical test utilizes a series of biochemical reactions to assess the abilities of bacteria to perform specific metabolic processes, such as fermentation of carbohydrates, utilization of amino acids, and production of specific enzymes. Each reaction produces a measurable change, which can be used to generate a profile that is characteristic of a particular species. By comparing these metabolic profiles against known databases, microbiologists can accurately identify the bacterial species in question. This process highlights the importance of understanding the metabolic characteristics that define different groups of bacteria.

The other options focus on different aspects of microbial identification. Colony morphology considers the physical characteristics of bacterial colonies but does not provide the detailed biochemical insight that the API test offers. Genetic sequencing provides a higher resolution identification based on DNA, but it is not the method employed in the API test, which focuses on metabolic functions instead. Staining reactions, such as Gram staining, classify bacteria based on their cell wall structure but do not directly assess their metabolic capabilities.