An Overview of Biological Basics - Bioprocess Engineering: Kinetics, Biosystems, Sustainability and Reactor Design - page 26

TABLE 2.2 Primary Subdivisions of Cellular Organisms that Have Been Recognized

Group Cell morphology Properties Constituent groups

Eukaryotes Eukaryotic Multicellular; extensive

differentiation of cells and tissues
Unicellular, coenocytic or
mycelial; little or no tissue
differentiation

Plants (seed plants, ferns, mosses)
Animals (vertebrates,
invertebrates)
Protists (algae, fungi, protozoa,
slime molds)

Eubacteria Prokaryotic Cell chemistry similar to

eukaryotes

Most bacteria

Archaea Prokaryotic Distinctive cell chemistry Crenarchaeota (sulfolobus,

therofilum, thermopteus,
pyrobaculum, haloquadratum
walsbyi)
Nanoarchaeota
Euryarchaeota (methanogens,
halophiles, thermoacidophiles)
Korarchaeota

information is contained in the DNA, whereas viruses can use either RNA or DNA to encode
such information. This nuclear material is covered by a protein coat called a capsid. Some
viruses have an outer envelope of a lipoprotein and some do not.
Almost all cell types are susceptible to viral infections. Viruses infecting bacteria are called
bacteriophages. The most common type of bacteriophage has a hexagonal head, tail, and tail
fibers as shown in Fig. 2.3 . Bacteriophages attach to the cell wall of a host cell with tail fibers,

DNA-containing head

Collar

Sheath

Base plate

Ta i l f i b e rs

FIGURE 2.3 The structure of a typical bacteriophage.