Τhe study of unicellular (single cell), multicellular (cell colony), or acellular (lacking cells) organisms, is the subject of Microbiology. It encompasses a wide range of sub-disciplines including parasitology, mycology, virology and bacteriology.
Eukaryotic micro-organisms possess membrane-bound cell organelles and include fungi and protists, opposite to the prokaryotic organisms—which comprise archaebacterial and eubacteria and are classified as not membrane-bound organelles. Microbiologists traditionally relied on staining, culture and microscopy. However, with current means less than 1% of the microorganisms present in common environments can be cultured in isolation. Microbiologists often rely on extraction or detection of nucleic acid, either DNA or RNA sequences.