Page 12 - Introduction to Microbiology

Scope of Microbiology

• Bacteria (singular: bacterium)

– Single-celled organisms with no cell nucleus and membrane-bound intracellular
structures found in cells of higher organisms

• Viruses

– Acellular entities that require other living cells to propagate

– Composed mainly of nucleic acid and a few proteins

• Algae (singular: alga)

– Many are single-celled microorganisms but some marine algae are large, complex

multicellular organisms
– Unlike bacteria, algae have clearly defined cell nucleus and intracellular structures

– All algae photosynthesize their own food and thus, are important source of food for

other organisms