Which of the following terms refers to bacteria resistant to environmental stress?

The term that refers to bacteria resistant to environmental stress is bacterial spores. Bacterial spores are a dormant form of bacteria that can survive extreme conditions, such as heat, drought, and toxic environments. This remarkable resilience makes them capable of withstanding harsh environments that would typically kill other forms of bacteria.

In contrast, mycobacterium refers to a genus of bacteria that include pathogens known for causing diseases like tuberculosis, but it does not specifically refer to stress resistance. Biofilms are structured communities of bacteria that adhere to surfaces, providing some protection to the bacteria within but not specifically indicating resistance to environmental stress in the same way spores do. Toxic bacteria refers to bacteria that produce toxins, which is a different concept from environmental resistance. Thus, bacterial spores are the most accurate choice when discussing bacteria that can withstand extreme environmental conditions.