Prokaryotes – Flashcards
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| Prokaryote |
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| A single-celled organism that lacks a nucleus and membrane-bound organelles |
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| What are the differences between Archaea and bacteria? |
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| Differences in rRNA and tRNA Unique cell wall/membrane components in archaea Archaea has repeated gene structures and introns Archaea has unique shapes |
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| How can prokaryotes be classified? |
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| Shape Gram staining Metabolism Habitat Genetics |
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| Cocci |
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| Sphere-shaped bacteria |
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| Diplococci |
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| Group of two balls (Cocci) |
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| Tetrad |
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| Group of four balls (Cocci) |
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| Sarcinae |
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| Groups of eight balls (Cocci) |
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| Bacilli |
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| Rod-shaped bacteria |
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| Diplobacilli |
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| Two rods attached end-to-end (Bacilli) |
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| Coccobacilli |
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| Rounded rod-shaped bacteria (Bacilli) |
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| Strepto- |
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| Indicates a chain-shaped bacteria |
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| Palisades |
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| Side-to-side arranged rods, generally not parallel. (Bacilli) |
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| Spiralla |
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| Curved or spiral-shaped bacteria |
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| Vibrios |
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| Curved rods, no rotation (comma-shaped) (Spiralla) |
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| Spirilla |
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| Bacteria that rotate at least one helical turn in their shape and have flagella at their polar ends. (Spiralla) |
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| Spirochete |
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| Bacteria that have at least three helical turns in their shape, with periplasmic flagella (Spiralla) |
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| Gram positive |
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| Bacteria with a thick, exposed layer of peptidoglycan |
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| Gram negative |
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| Bacteria with a covered layer of peptidoglycan, which the stain cannot attack |
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| Autotroph |
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| Obtains carbon from inorganic sources |
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| Heterotroph |
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| Obtains carbon from organic sources |
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| Chemotroph |
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| Gets energy from chemicals |
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| Phototroph |
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| Gets energy from light |
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| Obligate aerobes |
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| Require oxygen to make ATP |
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| Obligate anaerobes |
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| Require an oxygen-poor environment to make ATP |
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| Facultative anaerobes |
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| Can live in an aerobic or anaerobic environment |
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| What are the problems with traditional taxonomy? |
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| Traditional groups into which we classify bacteria can overlap - a specimen may fit into more than one group. Also, species within a group may not be related at all, meaning that a medicine that works on one species can't necessarily be expected to do anything for the rest of the group. |
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| What are the problems with phylogenetic taxonomy? |
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| To identify an organism phylogenetically, genetic screening has to be run, which takes more time than just looking at an organism or running one or two tests. Also, because it's so new, not many people know it the way they know the traditional system. |
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| Division I prokaryotes |
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| Gracilicutes Gram-negative |
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| Division II prokaryotes |
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| Firmicutes Gram-positive |
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| Division III prokaryotes |
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| Tenericutes No cell wall |
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| Division IV prokaryotes |
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| Archaebacteria |
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| What types of appendages can be present in prokaryotes? |
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| Axial filaments or flagella (for movement) Fimbriae or pili (for attachment) |
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| Flagellum |
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| A whip-like motility appendage. Comprised of a filament, hook, and basal apparatus. |
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| Monotrichous flagellum |
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| A flagellum at one polar end of a bacteria |
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| Lophotrichous flagella |
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| Multiple flagella originating from the same point |
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| Amphitrichous flagella |
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| Flagella on both polar ends of a bacteria |
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| Peritrichous flagella |
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| Flagella distributed randomly on the surface of the cell |
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| Peritrichous flagella |
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| Flagella distributed randomly on the surface of the cell |
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| Periplasmic flagella |
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| Flagella that are wrapped around the "body" of the bacteria in a spiral fashion |
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| Chemotaxis |
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| Movement in response to a chemical stimulant |
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| Phototaxis |
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| Movement in response to light |
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| Fimbriae |
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| Small, bristle-like appendages for attachment. Used in aggregation or colonization. |
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| Pili |
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| Appendages for reproduction, generally in gram-negative bacteria. Used to exchange genetic material. |
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| Glycocalyx |
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| An outer layer of a bacterium composed of macromolecules. It can serve to prevent dessication, protect against immune attacks (by causing antibodies to bind incorrectly), or encouraging colonization. |
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| Biofilm |
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| A thick layer of accumulated prokaryotes due to fimbriae and glycocalyces. These can be a problem in artificial joints, catheters, and dental hygiene. |
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| Quorum sensing |
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| The ability of a bacterial colony to "sense" its population density |
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| Cell envelope |
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| The set of structures that make up an external membrane complex. Includes the cell membrane, cell wall, and outer membrane. |
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| Cell membrane |
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| Made of phospholipids and proteins, this membrane (in prokaryotes) carries out many of the functions that membrane-bound organelles do in eukaryotes. |
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| Cell wall |
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| A peptidoglycan structure that serves to maintain cell shape and integrity. Not present in all prokaryotes. |
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| How can peptidoglycan serve as a target for drugs? |
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| Peptidoglycan is made of polysaccharide strands linked by peptide bonds. Drugs can disrupt those peptide bonds, loosing the strands and dissolving the wall. |
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| Outer membrane |
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| Structure seen only in gracilicutes. Its outer layer is composed of lipopolysaccharide (LPS), and its inner layer is composed of phospholipids and lipoproteins, which are attached to the cell wall. Traffic is regulated by porins. |
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| Why do some cell envelope components automatically trigger immune responses? |
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| Bacteria and humans have been around together a long time, so by now, immune responses to certain bacteria components are ingrained into our DNA. |
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| Cytoplasm |
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| The inside space of the cell. Comprised of 75% water, plus ribosomes, protein, and other cellular materials, plus a cytoskeleton network. |
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| Nucleoid |
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| Prokaryotic conglomeration of genetic material. Most have a single loop of DNA, others have extra genes. |
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| Plasmids |
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| Self-replicating "accessory" DNA that can be stored and shared freely among prokaryotes. |
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| What do plasmids mean for medicine? |
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| On the one hand, plasmids are bad news, because a virulent bacteria can pass on a drug resistance or toxin-containing plasmid to normally benign bactera, causing a totally new infection. On the other hand, we can engineer plasmids to contain beneficial genes, which we can then impart via bacteria to other organisms. |
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| Ribosome |
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| Protein-making machinery consisting of a 50S and 30S subunit, made up of rRNA and protein. |
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| Polysome |
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| A string of ribosomes that make protein from RNA in succession. |
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| Inclusion bodies |
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| In bacteria, intracellular nutrient stores enclosed by a single-layered membrane. In biology, it's a general term with many meanings. |
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| Cytoskeleton |
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| An intracellular network of actin filaments that help support the cell's architecture and provide "roadways" for cellular components to move. |
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| Sporulation |
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| Spore formation due to adverse environmental triggers. Seen in gracilicutes and firmicutes. |
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| Vegetative cell |
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| Metabolically active cell |
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| Endospore |
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| Spore form, metabolically inactive |
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| Why sporulate? |
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| Nutrients are scarce or the environment is wrong |
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| Genus Ricksetta |
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| Gram-negative prokaryotes that are obligate intracellular (they can't live outside a host). They cause RMSF and a form of typhus. |
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| Genus Chlamydia |
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| Gram-negative prokaryotes that can't exist outside a host, and were once considered viruses |
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| Genus Mycoplasmia |
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| Tenericutes, has an outer membrane but no cell wall. Has the smallest bacterial genome known, causes "walking pneumonia" and PID. |
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| Conjugation |
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| Bacterial "sex" - the exchange of genetic material though pili |
