Environmental Microbiology Talaro Chapter 26 1 Environmental Microbiology

Environmental Microbiology Talaro Chapter 26 1

• 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 2

Microbes comprise approximately half of all the biomass on Earth Prokaryotes exist in all of the habitats on Earth Extreme cold Prokaryotes exits in Extreme heat Low O 2 environments that are too Extreme pressure – “barophiles” extreme or inhospitable for now called piezophiles eukaryotic cells – High salt (low aw) 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 3

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

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 O 2 Millions to billions of years 5

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

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 7

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 • CH 4 is also produced in high amounts (belching!) • Sugars absorbed by animal and used for energy • Plants unable to fix atmospheric N 2 • Symbiotic bacteria infect roots • Plant requires nitrogen for proteins 8

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

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

• 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 11

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

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

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

Winogradsky Column Nutrient Cycling • 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 15

• Algae, cyanobacteria, aerobic heterotrophs – CO 2 + H 2 O CH 2 O + O 2 • Oxygenic photosynthesis More on • H 2 O is a source of electrons anoxygenic and oxygenic – CH 2 O + O 2 CO 2 + H 2 O photosynthesis • Aerobic respiration is few moments • H 2 S oxidizers – CO 2 + H 2 S CH 2 O + S + H 2 O • Anoxygenic photosynthesis • H 2 S is a source of electrons 16

• 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 – CO 2 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 H 2 S as an electron donor • Can use H 2 S in low concentrations 17

• Purple non-sulfur bacteria – CH 2 O + O 2 CO 2 + H 2 O (Chemoheterotrophs) – CH 2 O + O 2 CO 2 + H 2 O (Photoheterotrophs) – CO 2 + H 2 O CH 2 O + O 2 (Photoautotrophs) • Purple & Green sulfur bacteria – Anoxygenic photosynthesis – H 2, H 2 S or So SO 42 - • Sulfate reducers – SO 42 - S 2 - compound (H 2 S or Fe. S) 18

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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 20

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. 21

Photosynthesis developed 3 bya 22

Anoxygenic Photosynthesis – Anaerobic bacterial photosynthesis that does not produce O 2 – CO 2 + H 2 S (CH 2 O)n + S + H 2 O • H 2, H 2 S 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 CO 2 fixation • Hypothesized to be have become an endosymbiont of eucaryotes • Mitochondrion 16 S r. RNA sequences 23

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

• Start here next time 25

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 26

Some cyanobacteria fix nitrogen in specialized cells HETEROCYSTS. Provide anaerobic environment required for nitrogenase. 27

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). 28

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. www. botany. wisc. edu/. . . /Anabaena. Azolla 2. jpg A cyanobacterial endophyte (Anabaena spp. ) fixes nitrogen that becomes available to the water fern, Azolla. www. csupomona. edu 29

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 www. resa. net/nasa/antarctica. htm 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. 30

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

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

Anoxygenic bacterial photosynthesis Photosystem I Electrons from H 2 S are passed to ferredoxin NADP is reduced Autotrophic CO 2 fixation CO 2 (CH 2 O)n CO 2 + H 2 S (CH 2 O)n + S + H 2 O Oxidation of H 2 S is linked to PS 1 textbookofbacteriology. net 33

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

Electrons lost here must be replenished CO 2 (CH 2 O)n Calvin Cycle Electrons from PS 1 reduce ferredoxin Ferredoxin passes the electrons to NADP Oxygenic Photosynthesis Plants, algae and cyanobacteria ATP is generate by PS 2 ensures a constant supply of noncyclic photophosphorylation electrons H 2 O is source of electrons 35 textbookofbacteriology. net

Table 6. Differences between plant and bacterial photosynthesis Plant Photosynthesis Bacterial Photosynthesis Organisms plants, algae, cyanobacteria purple and green bacteria Type of chlorophyll a absorbs 650 -750 nm bacteriochlorophyll absorbs 800 -1000 nm Photosystem I (cyclic photophosphorylation) present absent yes no H 2 O H 2 S, other sulfur compounds or certain organic compounds Photosystem II (noncyclic photophosphorylation) Produces O 2 Photosynthetic electron donor textbookofbacteriology. net 36