Final answer:
The laboratory method to study bacterial populations in soil samples involves growing bacteria in controlled conditions, using subculturing techniques, and identifying them through selective and differential media.
Step-by-step explanation:
The laboratory method used to study the various bacterial populations in a given soil sample involves several techniques that provide bacteria with the appropriate nutrients, environment, and conditions they need to grow. This includes methods like pure culture growth, subculturing, and specific biochemical assays to identify and measure the growth of bacterial populations. For instance, preliminary steps such as enrichment culture are utilized to increase the number of bacteria in a sample to detectable levels. Then, through processes like subculturing, microbiologists can maintain and grow bacterial cultures by transferring them to new media periodically. Furthermore, scientists use various types of selective and differential media to distinguish between bacterial species based on phenotypic traits, which often require additional testing for definitive identification.