Microbes and Earth Materials Microbes are any life form too small to be seen with the naked eye Classification of life forms Eukaryotic Plants animals fungus algae and even protozoa Prokaryotic archaea and bacteria Living cells can Self feed Replicate grow Differentiate change in form function Communicate Tree of life diatom forams Archaea and Bacteria can vary in size Some are as large as 600 x 80 m Most are on the order of a 0 5 2 m Some are thought to be as small as 100 nm or smaller nanobacteria Your hair is around 35 m thick 35 000 nm Archaea and bacteria come in many shapes Cocci Bacilli rods Many others corkscrews helices spirals stars squares and more Spores analogous to seeds Prokaryote Structure Cell wall Nuclear material membrane Membrane is critical part of how food and waste are transported Selectively permeable Phospholipid layer Transport proteins Cell Nuclear Material Genetic information in the nucleoid single DNA molecule in a gel like form twisted and folded to fit inside the cell RNA around that they do the work both by carrying messages and catalyzing reactions Why is DNA and RNA important in thinking about microbes as an Earth material Identify organisms in environments Use genetic information for info about what they eat and how Understand evolutionary relationships Movement Flagella spin corkscrew motion Vesicles gas filled for buoyancy Cell Metabolism Based on redox reactions Substrate food electron is lost from this which is oxidized by this process that electron goes through enzymes to harness the energy for the production of ATP Electron eventually ends up going to another molecule which is reduced by this Nutrition value Eukaryotes like us eat organics and breathe oxygen Prokaryotes can use other food sources and acceptors Redox gradients and life Microbes harness the energy present from DISEQUILIBRIUM Manipulate flow of electrons O2 H2 O C2HO Other nutrients needed for life Besides chemicals for metabolic energy microbes need other things for growth Carbon Oxygen Sulfur Phosphorus Nitrogen Iron Trace metals including Mo Cu Ni Cd etc What limits growth Nutrient excess can result in blooms Diversity There are likely millions of different microbial species Scientists have identified and characterized 5 000 of these Typical soils contain hundreds thousands of different species Very extreme environments contain as little as a few different microbes Environmental limits on life Liquid H2O life as we know it requires liquid water Redox gradient conditions which limit this Range of conditions for prokaryotes much more than that of eukaryotes inactive stasis Spores can take a lot of abuse and last very long times Tougher living less diversity Closer to the limits of life Fewer microbes able to function Microbial evolution Oldest fossil evidence 3 5 g a Stromatolites Evidence for microbial activity argued for deposits 3 7 g a Couple fossil evidence with genomic information analysis of function from genetic info Put against backdrop of early earth conditions Significant atmospheric O2 after 2 0 g a Look at most primitive microbes in selected environments similar to early earth Tree of life Identifying microbes Morphological and functional what they look like and what they eat breathe Based primarily on culturing grow microbes on specific media trying to get pure culture Genetic Determine sequence of the DNA or RNA only need a part of this for good identification Probes Based on genetic info design molecule to stick to the DNA RNA and be visible in a microscope Microbes Minerals Direct precipitation dissolution Metabolism results in the precipitation of minerals excrete something that reacts with other ions to form minerals Utilize solids as e donors acceptors resulting in dissolution Indirect precipitation Changes in local environments e g pH Microbes may induce mineralization by forming shells testes Microbes may serve as templates for minerals to easily form on them Sulfate reducing bacteria Eat organics things like acetate and glucose Breathe sulfate exhale H2S H2S really likes metals form sulfide minerals Pyrite FeS2 Sphalerite ZnS Galena PbS etc White biofilm picture Iron Oxidizers Eat Fe2 Breathe O2 Fe3 product likes O OH forms oxyhydroxides FeOOH Goethite Schwertmmanite Amorphous FeOOH SEM of fluffy sampling picture Iron Reducers Eat Organics breathe Fe3 yielding Fe2 Get Fe3 from FeOOH minerals How to eat breathe a solid millions of times your size Solubilize the material Iron reducers use organics called siderophores to solubilize Fe3 and bring it inside the cell Also use special organics as shuttles which actually carry the electron between the microbe and the solid Magnetotactic Bacteria Form magnetic minerals from as a result of Fe3 reduction commonly magnetite Fe3 2Fe2 O4 and greigite Fe3 Fe2 S4 which are deposited inside the cell and used as a compass or sensor to guide the microbes position in an environment Microbes Direct Mineralization Through affecting metals sulfur and oxygen a number of minerals may be precipitated as a result of microbial metabolisms Microbes may also affect minerals through dissolution which yields increased weathering Sulfur oxidizing microorganisms Sulfur exists in different forms of varying redox state Microbes can use many of them as substrate using O2 NO3 Fe3 as electron acceptors O2 H2 O C2HO H2S oxidation Use H2S as e donor H2S is very reactive towards proteins and enzymes rips them up why it is toxic to humans Microbes that eat this are more resistant to this but will still die if exposed to too much H 2S Some of them oxidize the H2S to elemental sulfur S8 and store it in intracellular vacuoles Copyright 1997 Microbial Diversity Rolf Schauder S8 Beggiatoa spp colony Elemental Sulfur Oxidation Elemental Sulfur very hydrophobic Low pH environments abiotic dissolution very slow Several species of microbe can utilize S 8 as a substrate Pyrite Oxidation AMD neutralization Metals are soluble in low pH solutions can get 100 s of grams of metal into a liter of very acidic solution HOWEVER eventually that solution will get neutralized reaction with other rocks CO2 in the atmosphere etc and the metals are not so soluble but oxidized S sulfate SO42 is very soluble A different kind of mineral is formed Where is all the Fe2 coming from S in FeS2 goes to SO42 14 electrons Can be oxidized by Fe3 yielding Fe2 Microbes then eat Fe2 breathing O2 Fe3 Fe3 Sx FeS2 Fe2 Fe2 SO42 This is the principle reason behind the problem of Acid