1. Environmental Microbiology
Chapter 27
Environmental Microbiology

2. Metabolic Diversity
Microbes live in the most widely varied habitats on Earth
due to metabolic diversity
dynamic associations occur between microbes and ecosystem
Extremophiles
Most are Archaea
Produce specialized enzymes (extremozymes) that allow them to tolerate extreme conditions

3. Microbes live in an intensely competitive environment
High biodiversity
Competitive exclusion
Live in symbiotic relationships
Ruminants
Mycorhizae

4. Endomycorrhiza
Ectomycorrhiza

5. Soil Microbiology Billions of organisms in soil Over 80 % are bacteria
Millions in each gram of soil
Most are in the top few centimeters of soil
Biomining
Many antibiotics come from Actinomycetes
Streptomycin, tetracycline
Bacterial populations estimated by plate count

6. Biogeochemical cycles for carbon, nitrogen, sulfur and phosphorus are vital for life
Elements oxidized and reduced by microbes to meet their metabolic need
Recycles elements into the environment
Production
Consumption
Decomposition

7. The Carbon Cycle All organisms contain large amounts of carbon
Autotrophs fix CO2 into organics
1st step of carbon cycle
Heterotrophs consume autotrophs
2nd step of carbon cycle
Carbon reenters the environment as CO2
due to respiration; decomposition by microbes; burning fossil fuels
Global warming

9. The Nitrogen Cycle
Nitrogen is needed for synthesis of proteins and nucleic acids
Deamination
amino groups are removed and converted to ammonia
Ammonification
release of ammonia

10. Nitrification Denitrification oxidation of ammonium into nitrate
nitrate can be fully oxidized and used as an electron acceptor
Denitrification
leads to loss of nitrogen back to the atmosphere as nitrogen gas
Pseudomonas species are the most important soil denitrifying bacteria
Occurs in waterlogged soils where little oxygen is available

11. Nitrogen Cycle Proteins and waste products Amino acids
Microbial decomposition
Proteins and waste products
Amino acids
Microbial ammonification
Amino acids (–NH2)
Ammonia (NH3)
Nitrosomonas
Ammonium ion (NH4+)
Nitrite ion (NO2- )
Nitrobacter
Nitrite ion (NO2-)
Nitrate ion (NO3- )
Pseudmonas
Nitrate ion (NO3-) N2

12. Nitrogen makes up ~ 80% of the Earth’s atmosphere
Exists as nitrogen gas (N2)
Must be fixed into usable form
Specific microbes important in this conversion
Nitrogen fixation requires nitrogenase
Deactivated by oxygen
Nitrogen - fixation N2
Ammonia (NH3)

13. Two types of nitrogen fixers: Free-living
found in rhizosophere
Aerobic species - Azotobacter and Beijerinckia
Cyanobacteria –heterocysts
Anaerobic species - Clostridium

14. Symbiotic Rhizobia form root nodules on legume plants
Frankia associated with alder trees
Lichens when containing a cyanobacteria
Cyanobacteria & Azolla in rice patty water

16. The Sulfur Cycle Involves numerous oxidation states
Most reduced forms are sulfides like H2S gas
Generally forms under anaerobic conditions
Source of energy for some autotrophic bacteria
Convert reduced sulfur in H2S into elemental sulfur and oxidized sulfates
Thiobacillus
Endoliths

17. Winogradsky studied filamentous aquatic bacteria Beggiatoa alba
Revealed much about bacterial sulfur recycling and chemoautotrophy
Primary producers in deep ocean and endolithic communities are chemoautotrophic bacteria

18. Proteins decompose; sulfur released as H2S
Several photo-autotrophic bacteria use light for energy and use H2S to reduce CO2
Sulfates are incorporated into plants, animals and bacteria as disulfide bonds in proteins
Proteins decompose; sulfur released as H2S
Dissimilation

19. Sulfur Cycle Proteins and waste products Amino acids Amino acids (–SH)
Microbial decomposition
Proteins and waste products
Amino acids
Microbial dissimilation
Amino acids (–SH)
H2S
Thiobacillus
H2S
SO42– (for energy)
Microbial & plant assimilation
SO42–
Amino acids
Desulfovibrio
SO42–
H2S (reduced)

21. The Phosphorus Cycle Limiting factor for plant and animal growth
Exists primarily as phosphate ion (PO43-)
Little change during oxidation
soluble to insoluble; organic to inorganic
Often related to pH
Can be solubilized in rock by acids produced by bacteria like Thiobacillus

22. There is no product to return it to atmosphere
Accumulates in sea; certain islands are mined for phosphate deposits
Used in detergents and fertilizers
Runoff may lead to eutrophication

23. The Phosphorous Cycle