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7/30/2019 1ESC 590.Soil Biota.archaea Viruses
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Soil Biota
Reading Assignment
Soil Microbiology:An exploratory
ApproachChapters 10 & 11
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Archaea
Separable from bacteria both by theirmolecular phylogeny and phenology.
Cell membranes are unique. Basic structure of cell membrane is 5-C
isoprene unit
These are linked to form up to 20 chains
Chains are ether linked to glycerol, not esteras in bacteria and eucaerya.
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Halophiles have glycerol diether units;
Methanogens have mixed glycerol-dietherand diglycerol-tetraether units
In thermophilic archaea, tetraether
membrane are predominant
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Archaea
Divisions:3 major Kingdoms
1. Crenarcheota
2. Euryarcahaeota
3. Karorcaeota
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Archaea
1. Kingdom Euryarchaeota
- Representative Groups
1. Extreme Halophiles e.g Halobacterium 2. Methanogens e.g.Methanobacterium,
Methanococcus, Methanospirillum
3. Extreme thermophiles e.g.
Thermococcus, Thermoplasma
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Archaea
2. Kingdom Crenarchaeota
- Representative groups:
1. Thermoacidophiles e.g. Sulfolobus
2. Strictly anaerobic Crenarcahaeotes
e.g. Pyrodictum
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Archaea
Extreme Halophiles
Require High NaCl concentrations
Most grow best at 3-4 M Can go as a high as 5.2 M
Few can grow at 1.5 M
Counterbalance external NaClconcentration by accumulating highconcentration of KCl
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Archaea
Many produce red carotenoid pigment which
gives them protection from sunlight.
They are mainly aerobic and organotrophs Many use light drive cellular metabolism.
In cellular metabolism, cells use the pigment
retinal, the lack the plant and bacterial
chlorophylls.
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Archaea
Metahnogens
Strict anaerobes
Produce CH4 as metabolic products Methane emissions occur in marshes, swamps,
marine sediments; from intestines and rumens
of animals; and from sludge digesters and in
sewage plants.
Do not use sugars as a source of cell C.
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Archaea
CO2 is the major C source.
The C atom is reduced to CH4 by
electrons derived from hydrogen.Normally uses C with no C-C bond e.g.
formate, methanol.
Major source of natural methaneemissions.
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Archaea
Extreme Thermophiles
Constitute a diverse group of archaea
Has four genera:
1. Archaeoglobus,
2. Thermoplasma,
3. Thermococcus, and
4. Pyrococcus
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Archaea
Archaeoglobus
Strictly anaerobic and chemorganotrophic
Catabolizes sugars and simple peptides,
using sulfate as electron at the electronacceptor
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Archaea
Thermoplasma
Facultatively anaerobic
Grows best at pH 1.5 and 60oC
Genus does not have a cell wall external
to the cell membrane
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Archaea
Thermococcus and Pyrococcus
Two very similar except for differences
in their growth temperature Thermococcus grows optimally at 83oC
andPyrococcus at 100oC
Both are obligate anaerobes andchemorganotrophs.
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Archaea
Significance in Soil.
1. Serve to regulate soil bacterial population
2. May also function by allowing differentcompeting bacteria to coexist in soil.
3. They may participate in the decomposition of
plant materials.
4. Some are pathogenic e.gEntamoeba
histolytica which cases amoebic dysentry
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Viruses
The are submicroscopic agents
Consist of DNA or RNA molecules within
protein coats. Viral particles are metabolically inert and
do not carry out respiratory or bio-synthetic functions.
They induce a living host cell to producethe necessary viral components
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Viruses
After assembly, the replicated viruses
escape from the cell with the capability of
attacking new cells. Viruses infect all categories of animal and
plants, from humans to microbes.
Those parasitizing bacterial cells commonlyare called bacteriophages, or simply phages
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Viruses
Significance in Soil
Little is known about the field ecology of viruses
that infect soil organisms except that they persist
in soil as dormant units that retain parasitic
activities.
The ability of viral particles pathogenic to plants
or animals to survive in soil and move into thewater table is of major concern to people.