What are the differences between bacteria, fungi, viruses, protozoa, algae?

Answer 1

Bacteria: Belong to the domain of prokaryotes; single-celled; lack organelles and cellular compartments

Viruses: Infectious agents that are neither living nor non-living; can only replicate in other cells; classified according to the Baltimore classification system

Fungi: belong to the domain of eukaryotes; multi-cellular; mushrooms, yeast, mold etc belong to this group

Protozoa: single-celled eukaryotes

Algae: multi-cellular, photosynthetic eukaryotes

Answer 2

from (https://courses.lumenlearning.com/microbiology/chapter/types-of-microorganisms/):

Microorganisms differ from each other not only in size, but also in structure, habitat, metabolism, and many other characteristics. While we typically think of microorganisms as being unicellular, there are also many multicellular organisms that are too small to be seen without a microscope. Some microbes, such as viruses, are even acellular (not composed of cells).