Which type of microorganisms are single-celled and lack a nucleus?

The correct answer is bacteria, as they are indeed single-celled organisms that lack a nucleus. Bacteria fall under the category of prokaryotes, which are characterized by their simple cellular structure. Unlike eukaryotic cells, which contain a well-defined nucleus and other membrane-bound organelles, prokaryotic cells have no such compartmentalization. Instead, their genetic material, typically a single circular chromosome, is located in a region of the cell called the nucleoid.

Bacteria are immensely diverse and can live in a variety of environments, from extreme conditions (such as hot springs or deep-sea vents) to the human gut. They play crucial roles in various ecosystems, including recycling nutrients and participating in processes such as nitrogen fixation.

In contrast, viruses are not classified as living organisms since they cannot reproduce or carry out metabolic processes independently; they need a host cell to replicate. Fungi, while can be unicellular (as in yeasts), are classified as eukaryotes because they possess a nucleus and other cellular structures. Prions are infectious agents composed solely of protein, lacking any nucleic acid, and therefore do not fit the category of microorganisms in the traditional sense.

Understanding these distinctions highlights why bacteria are uniquely