Environmental Microbiology

1. Environmental Microbiology Talaro Chapter 26

2. Environmental Microbiology • Study of microbes in their natural habitats • Microbial Diversity – study of the different types of microbes in an environment • Microbial Ecology • Studies the interactions between microbes & their environments • Involving biotic & abiotic components • Distribution • Abundance – numbers of bacteria

3. Microbes comprise approximately half of all the biomass on Earth Prokaryotes exist in all of the habitats on Earth Extreme cold Extreme heat Low O2 Extreme pressure – “barophiles” now called piezophiles High salt (low aw) Prokaryotes exits in environments that are too extreme or inhospitable for eukaryotic cells – Extremophiles!! Limits of life on Earth are defined by the presence of prokaryotes which tells us what to look for when looking for life on extraterrestrial bodies

4. The primary role of microorganisms is to serve as catalysts of biogeochemical cycles textbookofbacteriology.net

5. Microbial catalysts interact on a much smaller spatial scale, but affect the biosphere over a long period of time Nanometers to micrometers Bacteria on the tip of a plant root Bacteria living in specialized organs of invertebrates Geologic Time Production of O2 Millions to billions of years

6. Microorganism have a greater metabolic versatility than do macroorganisms Photoautotrophs Chemoautrophs Photoheterotroph Chemoheterotrophs

7. Prokaryotes do not Exist in Isolation Plant and animals are dependent upon the actions of prokaryotes Archaea and Bacteria participate in mutualistic relationships that benefit both organisms Only a small number of bacteria are pathogenic! And there are bacteria that are pathogens of animals and plants

8. Examples of Mutualism • Sheep and cattle (ruminants) live off grass • Lack the digestive enzymes to break down cellulose • Bacteria in intestinal tract break down cellulose • Products of cellulose degradation are converted to carbon • sources that the ruminants can use • CH4 is also produced in high amounts (belching!) • Sugars absorbed by animal and used for energy • Plants unable to fix atmospheric N2 • Symbiotic bacteria infect roots • Plant requires nitrogen for proteins

9. Antarctica glaciers Hot springs Biofilms • Complex aggregation • Bacteria, archaea, protozoa, algae • Microbial Mat • Free floating organism • Attached organism • Highly structured • Extracellular polysaccharide • Protective & adhesive matrix • Protection from the environment • Protection from protozoans • Protection from antibiotics & chemicals Antarctic Sun February 12, 2006

10. Grows by cell division & recruitment • Industrial biofilms • Pipe corrosion • Ship corrosion • Infections • Dental plaque • Contact lenses • Heart valves • Artificial hip joints

11. Physiologically Integrated • Each group performs a specialized metabolic function • Lateral gene transfer • Conjugation between different species • Transduction between different species • Cell to cell communication • Quorum sensing

12. 1. Initial attachment 4. Maturation of Biofilm Architecture 2. Production of EPS 5. Dispersion 3. Early Biofilm Architecture

13. Microbial mat Cyanobacteria & purple bacteria Lake Cadagno, Switzerland White area is precipitated sulfur www.microbes.org/labs.asp

14. Cyanobacterial mat in run-off from a hot springs at Yellowstone National Park www.mit.edu/people/janelle/homepage.html

15. Nutrient Cycling Winogradsky Column • A glass column that simulates the complex interactions of microbial biofilms in an aqueous environment • Upper aerobic zone • Microaerophilic zone • Lower anaerobic zone Environmental Technology Consortium at Clark Atlanta University and Northern Arizona University 

16. Algae, cyanobacteria, aerobic heterotrophs • CO2 + H2O  CH2O + O2 • Oxygenic photosynthesis • H2O is a source of electrons • CH2O + O2 CO2 + H2O • Aerobic respiration • H2S oxidizers • CO2 + H2S  CH2O + S + H2O • Anoxygenic photosynthesis • H2S is a source of electrons More on anoxygenic and oxygenic photosynthesis is few moments

17. Purple nonsulfur photoheterotrophs • May exist as photoheterotrophs, photoautotrophs or chemoheterotrophs • Freely alternate between these metabolic modes depending on environmental conditions • Degree of anaerobiosis • Availability and types of carbon sources • CO2 for autotrophic growth • Organic compounds for heterotrophic growth • Availability of light for phototrophic growth • The “non-sulfur” label was used since it was originally thought that these bacteria could not use H2S as an electron donor • Can use H2S in low concentrations

18. Purple non-sulfur bacteria • CH2O + O2 CO2 + H2O (Chemoheterotrophs) • CH2O + O2CO2 + H2O (Photoheterotrophs) • CO2 + H2O  CH2O + O2 (Photoautotrophs) • Purple & Green sulfur bacteria • Anoxygenic photosynthesis • H2, H2S or So  SO42- • Sulfate reducers • SO42- S2- compound (H2S or FeS)

20. Quorum Sensing • Cell-cell communication in bacteria • Coordinate behavior/activities between bacterial cells of the same species • Autoinducers trigger a change when cells are in high concentration • Specific receptor for the inducer • Extracellular concentration of autoinducer increases with population • Threshold is reached • The population responds with an alteration in gene expression • Bioluminescence • Secretion of virulence factors • Biofilm formation • Sporulation • Competence

21. Energy & Nutrient Flow It is likely that most of the Earth's atmospheric oxygen was produced by bacterial cells. Plant cell chloroplast and oxygenic photosynthesis are originated in prokaryotes.

22. Photosynthesis developed  3 bya

23. Anoxygenic Photosynthesis • Anaerobic bacterial photosynthesis that does not produce O2 • CO2 + H2S  (CH2O)n + S + H2O • H2, H2S or So or organic compounds serves as a source of electrons • Need electrons to make fix C and make ATP • Purple and green photosynthetic sulfur bacteria • Aquatic & anaerobic • Pigments that absorb different l • Bacteriochlorophyll (800 - 1000 nm [far red]) • Carotenoids (400 - 550 nm) • Phycobilins are not present • Only 1 photosystem • Rhodobacter • Oxidize succinate or butyrate during CO2 fixation • Hypothesized to be have become an endosymbiont of eucaryotes • Mitochondrion 16S rRNA sequences

24. Cyanobacteria & purple bacteria Lake Cadagno, Switzerland www.microbes.org/labs.asp

25. Start here next time

26. Cyanobacteria Tremendous ecological importance in the C, O and N cycles Evolutionary relationship to plants Cyanobacteria have chlorophyll a, carotenoids and phycobilins Same chlorophyll a in plants and algae Chlorophyll a absorbs light at 450 nm & 650 - 750 nm Pycobilins absorb at 550 and 650 nm

27. Some cyanobacteria fix nitrogen in specialized cellsHETEROCYSTS. • Provide anaerobic environment required for nitrogenase.

28. Cyanobacteria have membranes that resemble photosynthetic thylakoids in plant chloroplasts. Hypothesized that cyanobacteria were the progenitors of eucaryotic chloroplasts via endosymbiosis. Cyanobacteria are very similar to the chloroplasts of red algae (Rhodophyta).

29. Several species of cyanobacteria are symbionts of liverworts, ferns, cycads, flagellated protozoa, and algae. The photosynthetic partners of lichens are commonly cyanobacteria. There is also an example of a cyanobacterium as endosymbionts of plant cells. A cyanobacterial endophyte (Anabaena spp.) fixes nitrogen that becomes available to the water fern, Azolla. www.botany.wisc.edu/.../AnabaenaAzolla2.jpg www.csupomona.edu

30. Several thousand cyanobacteria species. • Many are symbionts. • 200 species are free-living, nonsymbiotic procaryotes. Cyanobacteria often are isolated from extreme environments. Hot springs of the Yellowstone National Park Antarctica lakes Copious mats 2 to 4 cm thick in water beneath more than 5 m of permanent ice. Cyanobacteria are not found in acidic waters where algae (euckaryotic) predominate. www.resa.net/nasa/antarctica.htm

31. Green alga Figure 17. The distribution of photosynthetic pigments among photosynthetic microorganisms. Red alga cyanobacterium Green bacterium Purple bacterium textbookofbacteriology.net

32. Anoxygenic bacterial photosynthesis Photosystem I Cyclic Photophosphorylation Cyanobacteria, algae and plants, also have Photosystem II iron sulfur protein ATP is generated during photophosphorylation bacterial chlorophyll cyclic photophosphorylation

33. Anoxygenic bacterial photosynthesis Photosystem I Electrons from H2S are passed to ferredoxin NADP is reduced Autotrophic CO2 fixation CO2 (CH2O)n CO2 + H2S  (CH2O)n + S + H2O Oxidation of H2S is linked to PS1 textbookofbacteriology.net

34. Anoxygenic photosynthesis Limitations on the amount of C that can be fixed Need more electrons to fix more C

35. Oxygenic Photosynthesis Plants, algae and cyanobacteria Electrons lost here must be replenished PS2 ensures a constant supply of electrons ATP is generate by noncyclic photophosphorylation CO2 (CH2O)n Calvin Cycle Electrons from PS1 reduce ferredoxin Ferredoxin passes the electrons to NADP H2O is source of electrons textbookofbacteriology.net

36. Table 6. Differences between plant and bacterial photosynthesis textbookofbacteriology.net