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.

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1ESC 590.Soil Biota.archaea Viruses