ous parts of the human intestines and others live in marine environments.
Ecological characteristics include the ability to cause disease, temperature,
pH, and oxygen requirements of an organisms, as well as an organism’s
life cycle.- Genetic.Genetic characteristics classify organisms by the way in which
they reproduce and exchange chromosomes. For example, eukaryotic organ-
ismsreproduce sexually by conjugation where two cells come together
and exchange genetic material. Prokaryotic organisms do not reproduce
sexually and instead use transformation to reproduce. Transformation
occurs between strains of prokaryotes if their genomes are dissimilar but
rarely between genera.
In the early 1990s, T. Cavalier-Smith developed the two-empire and eight-
kingdom taxonomy based on phentic and phylogenetic characteristics. Phentic
measures the physical characteristics of an organism using a process called
numerical taxonomy. Numerical taxonomyis a phentic classification based on
physical measurements of an organism. Phylogenetic measures the evolutionary
relationship among organisms.
The two empires are bacteria and eukaryota. The bacteria domain contains
two kingdoms. These are eubacteria and archaeobacteria. The eukaryota empire
contains six kingdoms as shown in Table 9-1.
CHAPTER 9 Classification of Microorganisms^147
Empire Kingdom
Bacteria Eubacteria—Large group of bacteria that have
rigid cell walls.
Archaeobacteria—nonrigid cell walls.
Eukaryota Archezoa—Primitive one-cell eukaryotes.
Chromista—Photosynthetic organisms that
have chloroplasts within the lumen of the
rough endoplasmic reticulum.
Plantae—Photosynthetic organisms that have
chloroplasts in the cytoplasmic matrix.
Fungi—Absorb nutrients.
Animalia—Ingest nutrients.
Protozoa—Single-cell organism.Table 9-1. Cavalier-Smith Two-Empire and Eight-Kingdom Taxonomy