What type of bacteria reproduces by forming spores to protect themselves in adverse conditions?

The correct choice is spore former. This type of bacteria has the unique ability to produce spores, which are highly resistant structures that enable them to survive in conditions that are otherwise unfavorable for growth, such as extreme heat, desiccation, and the presence of toxic substances. The formation of spores allows these bacteria to remain dormant for extended periods until the environment becomes more suitable for growth and reproduction.

In contrast, facultative anaerobes are bacteria that can grow in both the presence and absence of oxygen but do not form spores as a means of protection. Mesophiles refer to bacteria that thrive at moderate temperatures, generally between 20°C to 45°C, but they also do not form spores. Aerobes specifically require oxygen for growth and, like the other groups mentioned, do not utilize spore formation as a survival strategy. Therefore, spore formers distinguish themselves by their ability to enter a dormant, resilient state in response to environmental stressors, which is crucial for their survival.