Final answer:
A contaminant in a liquid culture typically poses a more significant problem because it can rapidly spread and is challenging to isolate, making it harder to address than a contaminant on a streak plate, which can be more easily isolated due to separation of individual colonies.
Step-by-step explanation:
When comparing the effect of a contaminant landing on a streak plate versus in a liquid culture, each scenario poses different problems. A contaminant on a streak plate can be more easily isolated due to the method's aim to separate individual colonies.
This makes it possible to identify and subculture pure colonies. In contrast, a contaminant in a liquid culture can disseminate rapidly throughout the medium, making it a significant problem because it can lead to a homogeneous mixture that is hard to separate into individual species or strains. However, one could argue that contaminants in liquid cultures can sometimes be easier to detect through methods such as turbidity measurement or a rapid DNA or antibody testing when compared to the manual isolation required on a streak plate.
Overall, a contaminant landing in a liquid culture usually poses a bigger problem due to faster growth and the difficulty in isolating the contaminant once it is spread throughout the culture. Observing and inspecting the growth on a solid medium such as agar allows for easier differentiation of colony morphology, which can be critical in identifying microbial species or assessing purity.