PROKARYOTES. Chapter 16 Microbial Life: Prokaryotes & Protists. Review: Two different types of cells. Prokaryotes = Domain Bacteria & Domain Archaea

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1 Chapter 16 Microbial Life: Prokaryotes & Protists PROKARYOTES Review: Two different types of cells Prokaryotic Cells Eukaryotic Cells ( before-nucleus ) ( true-nucleus ) Ancient, single-celled organisms Single- or multi-cellular organisms Includes Bacteria and Archaea Membrane-bound nucleus holds DNA (most visible) No membrane-bound nucleus for DNA Membrane-bound organelles No membrane-bound organelles 1/10th Small: about Eukaryotic cell size of Internal compartments w/ specific metabolic functions Endomembrane system connects most organelles (work together) Prokaryotes = Domain Bacteria & Domain Archaea Used to divide life into Prokaryotes vs. Eukaryotes only then discovered Archaea still trying to categorize them. New genetic studies of prokaryotes and eukaryotes strongly support the three-domain view of life. Prokaryotes now classified into two domains: Bacteria and Archaea. (Third domain = Eukarya) *Archaea have at least as much in common with eukaryotes as they do with bacteria. biocourses/ N100/2k23domain.html Prokaryotes are diverse and widespread Most prokaryotes = Beneficial Though quite small and always unicellular, the collective biomass of prokaryotes =10x that of all eukaryotes. Several hundred species of bacteria live in and on our bodies, Often tolerate conditions eukaryotes cannot: decomposing dead skin cells, supplying essential vitamins, and guarding against pathogenic organisms. Hot / cold Prokaryotes in soil decompose dead organisms, sustaining chemical cycles. Acidic / alkaline Salty Some bacteria = pathogens (causing disease). Most bacteria on our bodies = benign or beneficial.

2 Prokaryotic cells have three common cell shapes Exterior Projections Benefit Prokaryotes Cocci are spherical prokaryotic cells. They sometimes occur in chains that are called streptococci. Nearly all prokaryotes have a cell wall: Bacilli are rod-shaped prokaryotes. Spiral prokaryotes are like a corkscrew. Short and rigid prokaryotes are called spirilla. Longer, more flexible cells are called spirochetes (i.e. Lyme Disease) provides physical protection prevents cell from bursting in certain situations. Some prokaryotes have extensions Flagella & Cillia aid in movement. Hairlike projections called fimbriae provide stickiness to substrate or each other. Populations of prokaryotes can adapt rapidly to changes in the environment Prokaryote population growth Genetic Variation in Prokaryotes The genome of a prokaryote typically occurs by binary fission (splitting in 2), has about one-thousandth as much DNA as a eukaryotic genome and can rapidly produce a new generation within hours is one long, circular chromosome packed into a distinct region of the cell (no nucleus). Many prokaryotes also have additional small, circular DNA molecules called plasmids, which replicate independently of the chromosome. Let s Talk About Food Prokaryotes have unparalleled nutritional diversity Two sources of energy are used. All living things need: 1. Source of Energy (to get electrons moving) 2. Source of Carbon (to build structures) Phototrophs capture energy from sunlight. Chemotrophs harness the energy stored in chemicals. Two sources of carbon are used. Autotrophs obtain carbon atoms from carbon dioxide. Heterotrophs obtain their carbon atoms from the organic compounds present in other organisms (by eating them).

3 Prokaryotes have unparalleled nutritional diversity Figure 16.UN01 Terms combined to describe modes of nutrition: Photoautotrophs obtain energy from sunlight and use carbon dioxide for carbon (e.g. plants). Photoheterotrophs obtain energy from sunlight but get their carbon atoms from organic molecules (rare: purple non-sulfur bacteria). Chemoautotrophs harvest energy from inorganic chemicals and use carbon dioxide for carbon (e.g. Nutritional mode Energy source Photoautotroph Chemoautotroph Inorganic chemicals Photoheterotroph Chemoheterotroph Carbon source CO2 hydrothermal vent bacteria). Chemoheterotrophs acquire energy and carbon from organic molecules (e.g. humans). Figure 16.4 ENERGY SOURCE Chemicals Chemoautotrophs CO2 CARBON SOURCE Photoautotrophs Where do we encounter Prokaryotes? Every day. Everywhere. All the time. Oscilliatoria Unidentified rock-eating bacteria Photoheterotrophs Chemoheterotrophs Rhodopseudomonas A Bdellovibrio attacking a larger cell Babies are colonized inside and out the moment they re born. Prokaryotes are the primary mode of decomposition after death. MammaMatters.com Biofilms are complex associations of microbes Biofilms complex associations of one or several species of prokaryotes (communicate, coordinate, share resources) may also include protists and fungi Prokaryotes attach to surfaces and form biofilm communities that are difficult to eradicate (e.g. drain scum) may cause medical / technical problems (e.g. tooth decay, corroding pipes). Prokaryotes help clean up the environment Prokaryotes useful for cleaning up contaminants (bioremediation) because they have great nutritional diversity, are quickly adaptable, and can form biofilms. Applications include sewage treatment and oil spills

4 Archaea thrive in extreme environments Archaea thrive in extreme environments Archaea living in extreme environments = Extremophiles unusual proteins and other molecular adaptations that enable them to metabolize and reproduce effectively. Extreme halophiles thrive in very salty places. Extreme thermophiles thrive in very hot water, such as geysers, and acid pools. Methanogens live in anaerobic (no O 2 ) environments, give off methane as a waste product from digestive tracts of cattle and deer decomposing materials in landfills PROTISTS Protists are an extremely diverse assortment of eukaryotes Protists diverse collection of mostly unicellular eukaryotes, may constitute multiple kingdoms within the Eukarya domain vague definition refer to eukaryotes that are not plants, animals, or fungi. Protists have diverse modes of nutrition Figure 16.13A Protists obtain their nutrition in many ways. Protists include Autotrophy Heterotrophy Mixotrophy autotrophs, called algae, producing their food by photosynthesis, heterotrophs, called protozoans, eating bacteria and other protists, heterotrophs, called parasites, deriving their nutrition from a living host, and mixotrophs, using photosynthesis and heterotrophy. Caulerpa, a green alga Giardia, a parasite Euglena

5 Protists live in diverse habitats Sample of Protist Diversity Protists live: anywhere there is moisture and Diatom In the bodies of host organisms. Dinoflagellate (red tide) Water Mold Parasitic protist from inside a termite gut Brown Algae Cilliate (giant kelp) More Microbial Diversity not easily classified Can algae provide a renewable source of energy? Fossil fuels are the organic remains of organisms that lived hundreds of millions of years ago and Radiolarian Excavates primarily consist of (dead, squished) diatoms and primitive plants. Amoeba Slime Mold Red Algae Green Algae Can algae provide a renewable source of energy? Lipid droplets in diatoms and other algae (i.e. protists) may serve as a renewable source of energy. If we can scale up, algae could produce biofuel. Still many hurdles to overcome for industrial-scale production