Microbiology Practice Exam 2026 – Comprehensive All-in-One Guide for Exam Success!

Bacteria are unicellular organisms characterized by their prokaryotic cell structure. This means that bacterial cells lack a defined nucleus and other membrane-bound organelles, which is a distinguishing feature of prokaryotes. Instead, their genetic material is typically organized in a single circular chromosome that floats freely in the cytoplasm. Bacteria play a diverse range of roles in various ecosystems and can be found in numerous environments, from soil to the human body. Their unicellular nature allows them to reproduce rapidly via binary fission, contributing to their ability to adapt and thrive under different conditions.

Fungi, on the other hand, are primarily multicellular (though some yeasts are unicellular), and they have a eukaryotic structure that includes a defined nucleus. Viruses are not considered living organisms in the traditional sense, as they cannot replicate independently and lack cellular structure; they require a host cell to reproduce. Protozoa are unicellular eukaryotic organisms, distinct from bacteria due to their complex cellular organization, which includes a nucleus and various organelles. Thus, bacteria uniquely fit the criteria of being unicellular and prokaryotic.