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Domain Bacteria Kingdom Eubacteria Quick Review Remember from earlier this year that there are two broad categories of organisms: *Prokaryotes – have No membrane bound organelle *Eukaryotes – have membrane bound organelle General Characteristics Prokaryotes (No membrane-bound organelle) Prokaryotes have a single, naked chromosome Some Prokaryotes have Plasmids, circular DNA Unicellular (single-cell) Cell Walls can contain peptidoglycan, not cellulose Cell Membranes made of bi-layered phospholipids First life forms, appeared approximately 3.5 BYA Flagella, if present, made up of Flagellin. Typical Prokaryote Cell Structure Internal Structure: Bacteria have a very simple internal structure, and no membrane-bound organelles. Nucleoid DNA in the bacterial cell is generally confined to this central region. Ribosomes Ribosomes give the cytoplasm of bacteria a granular appearance in electron micrographs. Translate the genetic message in messenger RNA into the production of proteins. Storage granules Stored foods in the cytoplasm in the form of glycogen, lipids, and sugars. Endospore Some bacteria, like Clostridium botulinum, form spores that are highly resistant to drought, high temperature and other harsh environmental hazards. Once the hazard is removed, the spore germinates to create a new population. Capsule Protects the bacteria cell. Outer membrane Bi-layer lipid found in Gram negative bacteria. Cell wall Composed of peptidoglycan (polysaccharides + protein), the cell wall maintains the overall shape of a bacterial cell. The three primary shapes in bacteria are coccus (spherical), bacillus (rod-shaped) and spirillum (spiral). Mycoplasma are bacteria that have no cell wall and therefore have no definite shape. Plasma membrane This is a lipid bilayer much like the cytoplasmic (plasma) membrane of other cells. There are numerous proteins moving within or upon this layer that are primarily responsible for transport of ions, nutrients and waste across the membrane. Pili These hollow, hairlike structures made of protein allow bacteria to attach to other cells. A specialized pilus, the sex pilus, allows the transfer from one bacterial cell to another. Pili (sing., pilus) are also called fimbriae (sing., fimbria). Flagella The purpose of flagella (sing., flagellum) is to move the cells. Flagella are long strands which rotate by means of a "motor" located just under the cytoplasmic membrane. Bacteria may have one, a few, or many flagella in different positions on the cell. Bacteria Escherichia coli E. coli Oxygen Preferences for Bacteria Obligate aerobes are organisms which must have oxygen to live. Obligate anaerobes cannot live in the presence of oxygen. Facultative anaerobes can live with or without oxygen. Nutrition Autotrophs- organisms that can make their own foods. Photosynthetic autotrophs- use light energy H20 & CO2 to make their foods. Chemosynthetic autotrophs - use inorganic compounds like Hydrogen sulfide and ammonia. Heterotrophs- obtain energy by consuming organic compounds, they cannot make their own foods. Most bacteria are “saprobes”, they get energy by eating dead, decaying matter; they are also called “decomposers” Endospores thick-walled structures that are highly resistant to harsh environmental conditions (high temperature, drying, oxygen, etc.); generally formed only by bacilli, and then each cell only forms one. endospore Locomotion (Methods of Movement) Bacterial Flagellum- lacks microtubules Classification Considerations Gram-staining characteristics Cell shapes and Groups Methods of obtaining energy Chemical Composition of the Cell Walls Gram Staining Gram-negative cells lack the ability to retain the deep violet dye because they have little, if any, peptidoglycan in their cell walls. Gram-positive cells have cell walls with large amounts of peptidoglycan which retain the deep violet dye and gives the cell a purple color. Gram Negative cell Gram Positive Cells Pink Purple Bacteria Photos E. coli Which of these cells are Gram +, Gram - ? Clostridium tetani Bacteria Photos Staphylococcus aureus Neisseria gonorrhoeae Cell Shapes and Groups Spherical-shaped cells Coccus (sng) , cocci (pl) A Group of Two is referred to as: Diplo…….. This is diplococccus A Cluster of cells is referred to as: Staphylo…. This is Staphylococcus Staph Infection Methicillin-resistant Staphylococcus aureus ….MRSA can mutate quickly to become resistant to the newest “last resort” antibiotics Bacteria are smart, antibiotics are dumb. What a slide of Typical coccus looks like in a microscope. A Chain of cells is referred to as: Strepto…. This is Streptococcus Strep Throat Rod-shaped cells Bacillus (sng) , Bacilli (pl) Typical Bacillus Bacillus http://er1.org/docs/photos/Anthrax/bacillus%20anthracis%20-03.jpg Typical Bacillus in a Microscope Spiral-shaped cells Spirillum (sng) , Spirlli (pl) Spirochetes Cyanobacteria are photosynthetic autotrophs that produce carbohydrates and oxygen tend to cling together in filaments or colonies The “heterocysts contain enzymes that allow them to “fix” atmospheric nitrogen Filamentous: Chain of cells http://www.spea.indiana.edu/joneswi/e455/Anabaena.jpg Anabaena _ http://www.bio.mtu.edu/~jkoyadom/algae_webpage/ALGAL_IMAGES/cyanobacteria/Anabaena_jason_dbtow17 2016.jpg Some filamentous cyanobacteria have Heterocysts: which are Nitrogen-fixing structures http://www.people.vcu.edu/~elhaij/IntroBioinf/Scenarios/heterocyst2.JPG Oscillatoria http://botit.botany.wisc.edu:16080/images/130/Bacteria/Cyanobacteria/Oscillatoria/Oscillatoria_MC.jpg Nitrogen-fixation Some soil bacteria live in the ground and take in Nitrogen from the surroundings The Nitrogen is combined with oxygen to form nitrites and nitrates…. Plants use the nitrates and nitrites to make proteins…. (Grow !!) Denitrification Some soil bacteria break down the nitrogen compounds and release the nitrogen back into the environment. Life would not exist as we know it without Nitrogen-fixing and Denitrifying bacteria. Asexual Reproduction Binary Fission – cells grow in size the split in two…. Genetically identical Sexual Reproduction in Bacteria (methods of exchanging DNA) Conjugation Two bacteria join together and transfer portions of DNA Transformation DNA from the environment is simply taken in by a bacterium Transduction A virus obtains DNA from a host bacterium Virus Bacterium Beneficial Uses Chemical Used recyclers (Nitrogen Cycle) in the dairy industry to make cheese, yogurts and sour cream. Genetic Engineering of HGH, Insulin, Etc… Oil spill cleanup Synthesis of Vitamins in your intestines Symbiotic Relationships – E. coli in the intestines of mammals aid in digestion. Mutualism – some bacteria are parasites…. They live in a host and eventually overpopulate…. As they do they use the host’s food, water and eventually starve the tissues. Parasitism Antibiotics How Antibiotics Work Many Ways…. • Antibiotics can prevent bacteria from making new cell walls. • Can disrupt Protein Synthesis * Disrupt many cell metabolic reactions Pathogens: disease-causing agents Escherichia coli (E. coli) – found in the intestines of mammals…. Can be deadly if the wrong species is eaten. Clostridium botulinum – causes “botulism” ….. food poisoning. Clostridium tetani – causes tetanus. Preventing Foodborne Diseases 1. Keep cooked and raw foods separate. 2. Wash fruits and vegetables before eating them. 3. Refrigerate leftovers.