Bacteria and Archaea: The
Prokaryotes
http://www.mhhe.com/biosci/genbio/raven6b/graphics/raven06b/othe
r/ch04.pdf
Kingdom Eubacteria
• Diverse kingdom of unicellular prokaryotes
• no membrane bound organelles
• Contains mostly mesophiles and neutrophiles
• Encompasses 21+ phyla, and includes gram positive, gram negative, and
proteobacteria.
• “Eu” bacteria = “true” bacteria
• http://highered.mcgrawhill.com/sites/0072320419/student_view0/chapter21/study_outline.html
• http://highered.mcgrawhill.com/sites/0072320419/student_view0/chapter22/study_outline.html
• http://highered.mcgrawhill.com/sites/0072320419/student_view0/chapter23/study_outline.html
• http://highered.mcgrawhill.com/sites/0072320419/student_view0/chapter24/study_outline.html
• http://kdhellner.tripod.com/id2.html
Eubacteria Phyla
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Gram positive: Includes three phyla with notable genera such as the
Mycoplasma(stains negative but is structurally positive), Ureaplasma and
Streptomyces, Phytoplasma.
Gram negative: Includes many phyla such as Spirochaetes which are a phylum of
double-membrane bacteria, most of which have long, helically coiled cells.
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Leptospira species, which causes leptospirosis (field fever)
Borrelia burgdorferi, B. garinii, and B. afzelii, which cause Lyme disease
Borrelia recurrentis, which causes relapsing fever
Treponema pallidum subspecies which cause treponematoses such as syphilis and yaws.
Proteobacteria: Includes many phyla which are all gram negative. They include a
wide variety of pathogens genre such as Escherichia (E. coli), Salmonella, Vibrio (V.
cholerae), and Helicobacter (H. pylori). Others are free-living (non-parasitic)
bacteria that are called purple bacteria, referring to their mostly reddish
pigmentation, they use photosynthesis to obtain energy.
Cyanobacteria: is a phylum of bacteria that obtain their energy through
photosynthesis. The name "cyanobacteria" comes from the color of the bacteria.
They are often called blue-green algae.
Kingdom Archaea
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“archae” bacteria= “ancient” bacteria
Contains most of the “extremophiles”
Prokaryotes- no membrane bound organelles
Encompasses 5 phyla, and includes the methanogens and
extreme halophiles and thermophiles.
Until 1977 archaea were classified as bacteria. Comparative
molecular biology studies gave new evidence for
reclassification as a separate domain and kingdom.
http://highered.mcgrawhill.com/sites/0072320419/student_view0/chapter20/stud
y_outline.html
http://plantphys.info/organismal/lechtml/archaea.shtml
http://kdhellner.tripod.com/id15.html
Archaea Phyla
• Methanogens: are microorganisms that produce methane as a metabolic
byproduct. Methanogens are usually coccoid or bacilli.
https://www.sciencenews.org/blog/science-ticker/microbes-indictedancient-mass-extinction
• Halophiles: Halophiles are organisms that live in high salt concentrations.
The fermentation of salty foods often involves halobacteria, as either
essential ingredients or accidental contaminants. One example is
Chromohalobacter beijerinckii, found in salted beans preserved in brine
and in salted herring. Tetragenococcus halophilus is found in salted
anchovies and soy sauce.
• Thermophiles Live in extreme temperatures such as those found in
geothermal vents. http://www.microbiologyonline.org.uk/aboutmicrobiology/introducing-microbes/archaea
Evolution
• Some scientific evidence shows that archaea are genetically
more closely related to eukaryotes than eubacteria.
• Eubacteria could not have survived in early Earth conditions.
• The fossil record doesn’t give a clear picture as to when the
distinction between archaea and eubacteria evolved but we
do know that fossils of “bacteria” like organisms are found in
rock formations that are about 3.5 billion years old and fossils
of the earliest “eukaryote” like organisms are seen in rock
formations that are around 1.5-2.1 billion years old
(Smithsonian).
• Therefore we can only hypothesize that archaea and
eubacteria share a common ancestor and that ancestor
evolved into two distinct lineages. One lineage continued to
evolve and became eubacteria, the other lineage became
archaea which over time evolved further to split in the
eukaryote lineage.
Environment
• Bacteria live in standard
terrestrial or marine
environments.
• The majority of eubacteria are
mesophiles live in standard
temperature ranges 20-45C.
Some thermophilic eubacteria
exist and are believed to be the
oldest eubacteria or the missing
kink between the evolutionary
branches.
• The majority of eubacteria are
neutrophiles and live in the
standard pH range of 4-8.
• The majority of eubacteria either
require oxygen and are aerobic.
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Archaea live in extreme terrestrial or
marine environments.
The majority of archaea are
extremophiles.
Acidophile An organism with optimal growth
at pH levels of 3 or below
Alkaliphile An organism with optimal growth
at pH levels of 9 or above
Anaerobe An organism that does not
require oxygen for growth.
Cryptoendolith An organism that lives in
microscopic spaces within rocks, such as pores
between aggregate grains
.Halophile An organism requiring at least
0.2M concentrations of salt (NaCl) for growth
Hypolith An organism that lives underneath rocks
in cold deserts
Metallotolerant capable of tolerating high levels of
dissolved heavy metals in solution
Cryophile An organism capable of survival, growth
or reproduction at temperatures of -15 °C or lower
for extended periods
Radioresistant Organisms resistant to high levels
of ionizing radiation, most commonly ultraviolet
radiation, but also including organisms capable of
resisting nuclear radiation
Thermophile An organism that can thrive at
temperatures between 45–122 °C
XerophileA n organism that can grow in extremely
dry, desiccating conditions
Morphology
• Bacteria are classified into
5 groups according to
their basic shapes:
spherical (cocci), rod
(bacilli), spiral (spirilla),
comma (vibrios) or
corkscrew (spirochaetes).
They can exist as single
cells, in pairs (diplo),
chains (strepto) or
clusters (Staphyo).
• Eubacteria are usually
between 1-5 microns in
size.
• Archaea are much smaller
at usually less than 1
micron.
• Some archaea have
unusual shapes such as
cubes and pyrimids but
most archaea are either
bacilli, cocci, or spirilla.
Cell Wall Composition
• Cell wall composition is determined by Gram staining, which uses a violet
and a red stain to distinguish between wall types.
– Violet/Iodine primary stain
– Alcohol wash
– Red counterstain
• Gram positive (+) bacteria have a thick peptidoglycan cell wall that soaks
up the violet stain giving them a violet appearance under the microscope.
• Gram negative (-) bacteria have a thinner peptidoglycan wall that is
surrounded by lipids. The alcohol wash removes the lipid layer as well as
the violet dye, then the red counterstain stains the thin wall a red/pink.
• Archaea do have have cell walls made of peptidoglycan. Their cell wall
composition varies in types of glycans. Archaea that stain as positive have
a think cell wall made of glycan that is not peptidoglycan. Archaea that
stain as gram negative have a thin cell wall, or no cell wall.
Metabolism
• Most Eubacteria are
heterotrophs- consume organic
compounds for growth.
• Chemoheterotrophs use
inorganic compounds for energy.
• Photoheterotrophs use light for
energy.
• Some Eubacteria are autotrophs
that produce their own
compounds for growth.
• Photosynthetic bacteria such as
Cyanobacteria are
photoautotrophs, they use light
as their energy source.
• Chemoautotrophs use inorganic
compounds for energy.
• Most Archaea are autotrophs- the
produce compounds for growth.
• Chemoautotrophs- they use
inorganic compounds like
hydrogen sulfide and ammonia to
create energy as well as
producing their own compounds
for growth.
• Some evolutionary scientists
believe that the first organisms to
inhabit Earth were heterotroph
which ate organic compounds
from the environment and
produced CO2. This allowed for
the evolution of photoautotrophs
which eat CO2 and produce
oxygen. “The Heterotroph
Hypothesis”
Growth and Reproduction
• Both bacteria and archaea reproduce asexually
through binary fission.
• Both bacteria and archaea perform conjugation- a
genetic exchange through a pilus link.
• Some eubacteria and NOT archaea have the
ability to form spores, called endospores, when
environmental conditions are unfavorable. This
allows them to survive until conditions are more
hospitable and the endospores can germinate.