
biol1110_bacteria(eubacteria&archaebacteria) 6/23/04
BIOL 1110 REEDER
THE BACTERIA (EUBACTERIA AND ARCHAEBACTERIA)
I. Bacteria
A. General Characteristics
1 Believed to be the oldest life forms
a. Oldest fossils found to date: 3.8 billion years old resembling contemporary
photosynthetic blue-green bacteria (stromatolites)
2. Are the simplest and most abundant microorganisms
3. Inhabit every possible place where life can be found including in or on other organisms:
a. relatively few places in the world devoid of bacteria
b. tremendous biological success due to small size, reproductive ability, rapid rate of
mutation, ability to live almost anywhere, and form capsulated spores in a state of
suspended animation during unfavorable environmental conditions
4. Lack membrane-bound organelles and the genetic material is contained in a single circular
DNA molecule in the cytoplasm (nucleoid: haploid), not surrounded by a nuclear membrane:
PROCARYOTIC
a. Small amounts of genetic information may be present as smaller DNA molecules called
plasmids which replicate independently of the chromosome and often bears genes
involved in antibiotic resistance; subject of Recombinant DNA research; extra-
chromosomal DNA
5. Generally are smaller than eucaryotic cells, which may be attributed to the lack of cellular
organelles; [um (micron) = 0.001mm]
a. Procaryotes: 1 to 10um
b. Eucaryotes: few smaller than 7um
6. Very rapid growth and division, which often exceed a billion cells per milliliter of growth
medium
a. Because of rapid growth rates, genetic variability as a result of mutation is considerable
B. Taxonomy
1. Kingdom Eubacteria (holds principal forms)
a. Bacteria; formerly Kingdom Monera or Prokaryotae
b. Includes blue-green bacteria ("algae") or cyanobacteria
2. Kingdom Archaebacteria
a. Biochemically, are different from the other bacteria
1) Absence of peptidoglycan from their cell walls
2) Appear to be adapted to conditions characteristic of early earth (extreme
environments) particularly with extreme temperatures
b. Three major ecological subgroups:
1) Methanogens: anaerobic, deriving energy (ATP) from CO2 and H2 to CH4 (methane);
inhabit swamps, sediments and animal intestinal tracts
2) Halophiles: can live only in extremely salty environments (hypertonic); most are
aerobic heterotrophs; some are photosynthetic
3) Thermoacidophiles: normally grow in hot, acid environments as hot sulfur springs
near volcanic vents at the ocean floor or near waste piles of coal mines
C. Bacterial Form and Function
1. Characteristic cell shape that is maintained by a rigid cell wall in most forms
a. Common shapes
1) Coccus
(cocci, pl.): spherical
2) Bacillus (bacilli, pl.): rod-like or cylindrical; most bacterial species