Texas A&M University (TAMU) BIOL206 Introductory Microbiology Lab Practice Exam 1

The least resistant form of microorganisms is bacteria in the log phase. During the log phase, bacteria are actively dividing and metabolizing, making them more susceptible to environmental stresses such as changes in temperature, desiccation, and exposure to antimicrobial agents. This is primarily because their cellular machinery is actively engaged in processes such as replication and protein synthesis, which can be disrupted easily compared to more dormant or resistant forms.

In contrast, viruses, fungal spores, and bacterial endospores offer varying levels of resistance. Viruses rely on host cells for replication and are generally more fragile outside their host organisms but can still be resilient. Fungal spores are quite resistant to environmental conditions, serving as a means of survival. Bacterial endospores are among the most resistant forms of microorganisms, capable of surviving extreme conditions such as heat, desiccation, and chemical exposure, which allows them to endure harsh environments for extended periods.

Therefore, when considering the various states of microorganisms, bacteria in the log phase represent the least resistant forms, as they are highly metabolically active and vulnerable to adverse conditions.