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Domains (and Kingdoms) Archaea and Eubacteria
PROKARYOTES Domains (and Kingdoms) Archaea and Eubacteria
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General Characteristics
All single celled, some form colonies. Oldest life forms. Can live almost anywhere! 2 domains: Eubacteria and Archaea. Single circular strand of DNA not encased in a nuclear membrane. No typical organelles (but have ribosomes). VERY small in cell size: µm. Variety of shapes, but most commonly: spheres (cocci), rods (bacilli), and spirals (spirilli)
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Anatomy The prokaryotic genome has less DNA than the eukaryotic genome
Most of this genome is a circular chromosome, located in the NUCLEOID REGION. Some species also have smaller rings of DNA called PLASMIDS. Reproduce quickly by BINARY FISSION and can divide every 1-3 hours, some even every 20 minutes- this leads to rapid evolution. Many form metabolically inactive ENDOSPORES which can remain viable in harsh conditions for centuries.
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Bacterial Plasmid Endospore Formation
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Movement Most motile bacteria propel themselves by FLAGELLA.
Many bacteria exhibit TAXIS, the ability to move toward or away from certain stimuli (light, chemicals, etc.).
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Cell Wall Maintains shape, provides protection, and prevents cell bursting. Made of PEPTIDOGLYCAN (except Archaea) Can be either GRAM POSITIVE and GRAM NEGATIVE – this is determined by a staining technique.
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Cell Wall, Cont’d. A polysaccharide or protein layer called a CAPSULE covers many prokaryotes Some prokaryotes have FIMBRIAE (AKA ATTACHMENT PILI) which allow them to stick to other individuals in a colony SEX PILI are longer than fimbriae and allow for exchange of DNA.
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Gram Staining GRAM POSITIVE:
- A thick peptidoglycan layer between two membrane layers. - Holds onto blue stain (CRYSTAL VIOLET). GRAM NEGATIVE: A thin peptidoglycan layer between two membrane Loses crystal violet easily and stains red (SAFRANIN). More likely to be antibiotic resistant (because many antibiotics target peptidoglycan and damage bacterial cell walls).
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Gram Staining
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Bacterial Genetics Prokaryotes have considerable genetic variation due to 3 factors: RAPID REPRODUCTION, MUTATION, and GENETIC RECOMBINATION DNA from different bacteria can be brought together by 3 processes.
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Bacteria Recombination
3 Processes: CONJUGATION - Only one part of a chromosome from one bacterium is transferred to a recipient thru a pilus. TRANSFORMATION - Living bacterium picks up pieces of DNA released into medium from other bacteria. TRANSDUCTION - Fragments of DNA are carried from one bacterium to another by a virus.
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CONJUGATION
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TRANSDUCTION
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Ecological Relationships
Decomposers – Break down dead matter and return nutrients to soil. Producers – Cyanobacteria are involved in photosynthesis and O2 production (and are also an important part in food chains). Nitrogen Fixers – Some bacteria, like Anabaena and Rhizobium, convert N2 in the atmosphere to more accessible forms such as nitrates (NO3) and nitrites (NO2). A specialized cell in Anabaena called a HETEROCYST does the nitrogen-fixing.
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Rhizobium
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Oxygen Requirements Bacterial metabolism varies with respect to O2
OBLIGATE AEROBES require O2 for cellular respiration OBLIGATE ANAEROBES are poisoned by O2 and use fermentation or anaerobic respiration. FACULTATIVE ANAEROBES can survive with or without O2.
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Metabolism CHEMOAUTOTROPHS use chemicals, such as H2S and NH3 to make energy. PHOTOAUTOTROPHS use sunlight to make energy (Cyanobacteria – like Anabaena and Oscillatoria). HETEROTROPHS (which include decomposers and pathogens).
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DOMAIN ARCHAEA Share certain traits with bacteria and other traits with eukaryotes. Absence of peptidoglycan in the cell wall. Tend to live in extreme environments (termed EXTREMOPHILES).
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Classification of Archaea
HALOPHILES: Live in salty environments. Typically red in color
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METHANOGENS: THERMOPHILES: Strict anaerobes that produce methane gas.
Found in swamps, sewage, human gut, and landfills. THERMOPHILES: Grow in hot (and usually acidic) environments. hydrogen sulfide gas may be present. Present in sulfur springs (like at Yellowstone Park) with 140°F water and a pH of 1 to 2. Thermophiles at deep sea hydrothermal vents can withstand water temperatures over 230°F.
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Domain Bacteria Largest prokaryotic group.
Strong cell walls made of peptidoglycan Some have slime layers for protection and attachment. Some form endospores in response to unfavorable conditions. Can withstand extreme conditions and last large amounts of time. Categorized based on 3 things: Metabolism Staining Shape
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Bacterial Shapes COCCUS: Round shape.
“Strepto” – Long chains (Streptococcus - "strep throat" and pneumonia). “Staphylo” - Bunches (food poisoning, skin infections) BACILLUS: Rod (rectangle) shaped. Ex.- Diphtheria, Typhoid fever, Tuberculosis) Clostridium botulinum and Salmonella cause food poisoning. Escherichia coli live in your intestine.
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Bacterial Shapes Cont’d
SPIRILLUM: Spiral shaped Syphilis (STD) is a common example FILAMENTOUS: Chain of cells all working and communicating together. Mostly found in cyanobacteria like Anabaena and Oscillatoria.
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Spirillum Coccus Bacillus Streptococcus Staphylococcus Spirillum Filamentous Filamentous
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Gram Negative Bacillus
Gram Negative Spirillum Gram Positive Coccus
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STREPTO- COCCUS
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STAPHYLO COCCUS
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Pneumonia Streptococcus
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Tuberculosis Bacteria
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Tuberculosis Bacteria Attaching To Cell Receptors
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Clostridium
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Salmonella
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Salmonella typhi (Typhoid Fever)
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White Blood Cells Attacking Bacteria
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