Final answer:
A visible colony represents the accumulation of microorganisms in or on a nutrient medium. MIC determination, growth curve analysis, and the use of selective and differential media are essential methods in microbiology to study bacterial growth and identify specific pathogens.
Step-by-step explanation:
The visible accumulation of microorganisms in or on a nutrient medium is known as a colony. In laboratory settings, microbiologists use various growth media to cultivate and study microorganisms. When observing colonies, the minimum inhibitory concentration (MIC) is the lowest concentration of an antimicrobial that will inhibit the visible growth of a microorganism after overnight incubation. This can be determined using macrobroth dilution tests or microbroth dilution tests in multiwell plates.
Observing the growth curve is crucial, as it allows scientists to understand how microorganisms proliferate in a closed environment, known as a batch culture. Key points in the growth curve include the lag phase, the logarithmic (log) phase, the stationary phase, and the death phase, the latter of which is characterized by an exponential decrease in viable cells.
Microorganisms have different strategies to support their growth. In aquatic systems, excessive nutrients can lead to oxygen depletion due to microbial growth. Continuous cultures like chemostats are used in industrial processes to maintain microorganisms in the log phase by steadily supplying nutrients and removing waste and dead cells. Colony growth on selective and differential media can indicate the presence of specific bacterial pathogens in food samples; however, additional tests are necessary to confirm contamination and identify the specific bacteria present. Selective media allows for the growth of specific microorganisms, while differential media will enable technicians to distinguish between organisms based on biochemical reactions that often result in visible changes, such as a color change.
Biofilms represent a common form of microbial life in nature, where microorganisms form complex and organized communities on various surfaces. These provide certain advantages to microorganisms, such as protection and optimized nutrient access To enrich cultures with specific types of bacteria, such as those capable of breaking down crude oil, repeated subculturing on a suitably selective medium is performed. Identification of bacteria using selective and differential media is thus a powerful tool in microbiological research and diagnostics.