Download Archaea and Bacteria Chapter 27

Archaea and Bacteria Chapter 27
Study the wall structure of gram positive and gram negative bacteria.
Understand the functions and differences between fimbrae, pili and flagella in bacteria.
Study the structure and action of bacterial flagellum.
Study the organization of DNA in chromosome (nucleoid) and plasmid.
Describe role of endospore and binary fission in bacteria.
Explain transduction or transformation or conjugation. Important terms include F plasmid, Hfr
bacterium, donor and recipient bacteria, and role of R plasmid in resistance.
Study the phylogenetic tree of 3 domains and table registering characters of 3 domains.
Study the table registering Major Nutritional Modes.
Five Groups in Bacteria
1. Prtoeobacteria is large diverse clade of gram negative bacteria and has 5 subgroups:
a. Alpha Prtoeobacteria includes many species of bacteria living inside eukaryotic organisms.
Rhizobium is N-fixing bacteria in root nodules of legumes. Agrobacterium makes tumors in
plant cells. Scientists use it to deliver foreign genes in cells of crop plants. Mitochondria
evolved from alpha Prtoeobacteria.
b. Beta proteobacteria is diverse group. Nitrosomonas lives in soil and converts NH4+ to NO3c. Gamma proteobacteria is another diverse group. Autotrophic sulfur bacteria Thiomargaria
namibiensis, Salmonella causes food poisoning, Vibrio cholerae causes cholera and
Escherichia coli lives in colon.
d. Delta proteobacteria includes slime secreting myxobacteria. When soil gets dry these
bacteria aggregate into fruiting body and release myxospores. Bdellobacteria attack other
bacteria and bore into at great speed.
e. Epsilon proteobacteria include pathogenic bacteria. Campylobacter causes blood poisoning
and intestinal inflammation. Heliobacter pylori causes stomach ulcers.
2. Chlamydeas are parasites and can only survive in animal cells. Chlamydia trachomatis is most
common cause of blindness in world and also causes STD, nongonococcal urethritis.
3. Spirochetes are helical heterotrophs. These use internal flagellum to rotate and locomote. Many are
free living but others cause serious diseases; Treponema pallidum causes syphilis and Borrelia sps
causes Lyme disease spread by ticks.
4. Cyanobacteria are unicellular or multicellular photoautotrophs. Cyanobacteria have Chlorophyll a
for photosynthesis like algae and plants. Oscillatoria has a trichome of photosynthetic cells. Nostoc
has mostly photosynthetic cells but also Heterocysts, swollen cells that fix atmospheric N2 to NH3. In
Anabena photosynthetic cells and Heterocysts undergo metabolic cooperation by exchanging
materials produced by them. Cyanobacteria are among most nutritionally independent organisms
and are pioneers (first colonizers) to colonize bare places like rocks.
5. Gram Positive Bacteria rival the proteobacteria in diversity.
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a. Actinomycetes form colonies having branched fungus like bodies and like them form chains
of spores. Most of them are free living decomposers in soil and are responsible for earthy
odor of rich soil. Pharmaceutical companies cultivate Streptomycetes to procure many
antibiotics (bactericidal drugs). Two species of actinomycetes cause tuberculosis and
leprosy.
b. Gram positive bacteria include solitary species like Bacillus anthracis which causes Anthrax
and Clostridium botulinum which causes food poisoning. Streptococcus and Staphylococcus
are gram +.
c. Mycoplasmas have the smallest cells (0.1μm diameter). Mycoplasmas are only known
bacteria without cell walls. These have very small genomes (517 genes in Mycoplasma
genitalium). Many are free living soil bacteria but others are pathogens.
ARCHAEA: multiple kingdoms
a. These prokaryotic organisms of ancient origin discovered first living in extreme
environments.
b. Archaea lack peptidoglycan in cell wall.
c. Like bacteria archaea are prokaryotes, divide by fission and have circular DNA.
d. Like Eukarya, some Archaea have histones associated with DNA
e. Introns in genes and many kinds of RNA polymerases
f. Their growth is not slowed by antibiotics like streptomycin or chloramphenicol.
These include:
Extremophiles:
6. Halophiles – these can tolerate very high concentrations of salts (Greek halo means salt) and live in
places like the Great Salt Lake and the Dead Sea. Some can tolerate high salinity but others need
many times salinity than sea water (3.5%) and die if gets lower. Halobacterium dies below 9%
salinity. These have special proteins and cell wall to tolerate high salinity.
7. Thermophiles – these can tolerate very high temperatures >90⁰C. These have branched
hydrocarbons in cell membrane. Sulfolobus archaea live in sulfur rich volcanic springs at 90⁰C.
Geogemma barossi lives at 121⁰C around hydrothermal vents. Ordinary organisms die at high
temperatures because their DNA loses its double helical structure and proteins get denatured and
lose their important functions. DNA polymerase from archaea is used in PCR technology to magnify
concentration of desired DNA.
Moderate Archaea: are archaea living at normal conditions of temperature or salinity.
Methanogens – These use CO2 as source of oxygen to oxidize H2 and produce methane, CH4, the
marsh gas as bye-product in marshes. Other species live in gut of cattle, termites or other
herbivores. Methanogens are strict anaerobes and very little amount of O2 kills them.
8. Euryarchaeota (Eury = wide range) include most extreme halophiles and methanogens and also
some extreme thermophiles.
9. Crenarchaeota (Cren = spring) include most extreme thermophiles.
10. Recently many species of both euryarchaeota and crenarchaeota have been discovered in ordinary
habitats like farm soil, lake sediments or surface waters in open seas.
11. New clades discovered recently include Nanoarchaeota, very tiny archaea in hydrothermal vents
and other habitats. Korarchaeota discovered in hot springs in yellow stone national park do not
seem to belong to either euryarchaeota or crenarchaeota.
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