Lecture 8, 9-17-07 Prokaryotic Structure

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• • candida albicans – causes yeast infections, vaginitis, thrush, nail infections. It is not a strong pathogen, it is opportunistic (have to give it an opportunity). It is localized infection. If someone has C.A. you would assume that they have AIDS
• • Infections are categorized into two groups Localized or generalized.
• • Mold pathogens
• pneumocystis jiroveci – causes PCP – pneumocystic pnemoniae. Common cause of death in AIDS patients
• • Ring Worms – very common
• o tinea pedis – athletes foot
• • important mold structures
• penicillium
• aspergillus
• rhizopus
• • Giardia lamblia - get it from water contamination
• • plasmodium – causes malaria. Vector is mosquito
• • bio terrorism agents
• Category A - common.
• • Variola major (Smallpox)
• • Bacillis anthracis (anthrax)
• • Yersinia pestis (plague)
• • Clostridium botulinum neurotoxins (botulism)
• • Francisella tularensis – rabbit fever
• This organism can go through your skin
• Category B
• • Coxiella burnetti – causes Q fever
• • Brucella – tough organism
• Prokaryotic structure
• Endospores – survival mechanism (not a reproductive mechanism) Very resistant. Only some have spores, clostridium and bacillus. Disinfectant does not necessarily kill spore formers.
• • Dipikalynic acid makes these things very resistant.
• Plasmids – tiny pieces of circular DNA
• • Example: E. coli
• • Involved with non essential functions. Such as antibiotic resistance.
• • MRSA – antibiotic resistance
• • Importance: genetic engineering
• Vacuoles – simply air bubbles
• • Example: Cyanobacteria (blue-green algea) – form bubbles and come up to the top of the water to get light in order to photosynthesize then they come back down.
• Chromatophores – membrane bound structures
• • Contain photosynthetic bacteria like chromatiom
• Cell membrane/mesosome
• • Selectively permeable walls.
• • Usually a tri layered structure.
• • Visualized as protein ships floating in a sea of phospholipids.
• • Sight of energy yielding reactions (mitochondria – tied to the membrane)
• • Primarily the same throughout the world (some differences between prokaryotic cell and eukaryotic cells)
• • Mesosome is an infolding of the membrane. Close to the chromosome because it has the energy (ATP).
• Cell wall
• • Different in gram (+) and gram (-)
• • Gram (+) cell walls are twice as thick as gram (-). Composed primarily of one layer which consists of peptidoglycan. Techoic acids are on the outside and they give the antigenic character to the gram (+) organism.
• • Gram (-) cell wall is half the size of the gram (+). Peptidoglycan is buried on the inside. Has a lot of proteins on the outside which give it its antigenic character. It has better defined pores.
• Peptidoglycan – rigid layer that gives shape to organisms
• • Visualized as a net.
• • Composed of amino sugars – nuramic acid and glucosamine. Usually have an amino acitile group attached to the amino group called Inacitile meramic acid sometimes called NAM. This is connected to NAG inacitile glucosamine. You have a huge polymer of NAM + NAG + NAM + NAG. These must be connected with amino acid side chains which is where you get the peptido from (peptide). The NAM + NAG is the “glycan” part.
• • Why is peptidoglycan important:
• Lysosyme acts at this level. It breaks the bond between NAG and NAM. A common source of lysosyme is tears.
• • Penicillin interrupts amino acid cross links
• • Penicillin reacts better to gram (+) because peptidoglycan is on the outside.
• Unique components of cell wall
• • Muramic acid is in both gram (+) and gram (-) because it is part of the peptidoglycan
• • Techoic acid, found only in gram (+).
• • DAP diamino pymelic acid -(don’t confuse it with DPA (di pikalynik acid) which is found in spores) Found in gram negative cell wall.
• • LPS – lipo polysaccharide (dark H’s with strings coming out, see handout). Part of gram (-) cell wall. The dark H’s are Lipid “A” which is very toxic and the strings coming out are the polysaccharides. This is important because LPS is known as the endotoxin. If you ever get gram (-) in your blood and the body tries to take them out then they lyse the organism and release the endotoxin.
• Outside of the cell wall
• • Glycocalyx (made out of sugars) – 2 groups: capsules and slime layers.
• • Capsules – distinct part of cell, well defined.
• Simple – Dextran (sometimes called glucan) - streptococcus mutans (gives you cavities), B anthracis: unique because it is only made of one amino acid
• Complex – made out of sugars, sugar acids, amino sugars
• • Strep pneumonea (causes primary pnemoniea)– pathogenic because of the capsule.
• • Clost. Perfringens - causes gas gang green and turkey day food poisoning
• • Kleb pneumoniae – causes secondary pneumonia. Can also cause urinary tract infections.
• Function of capsules – good adhesion
• • Capsules help organisms get around phagocytosis.
• Antiphagocytic capsule.
• • Outside source of energy.
• • Slime layers
• Loosely bound. Here today and gone tomorrow, they can float away.
• • Flagella
• Only some have flagella. Can range from one to 10 micrometers in length.
• If something moves it is the protein that does it. Flagella movement is the same way. This requires energy which means it is located near the cell membrane.
• Very thin and hard to see
• 3 types
• • Monotricous flagellation – many psuedomongus fall into this category
• • Amphitricous flagellation – flagella off of both ends.
• • Peritrichous flagellation – flagella all over the perimeter. The proteus organisms fall under this group and are very motile. Salmonella is also very motile.
• • Pili – smaller than flagella.
• Sexual pili (conjugation) – used in a linking up process. What happens is DNA is transferred one cell to the other (linked) through the sexual pilis. This is NOT sexual reproduction. They divide by binary fission, start with two cells and end up with two cells.
• Asexual pili – used for adhesion (primarily used by pathogens). Link up with a host cell. Examples: Niceria goneria- the clap and bordetella pertussis- whooping cough.
• • Molds and yeasts, the Fungi – Eukaryotic cells
• Yeasts are singular cells and are called Unicellular fungi – reproduce by budding.
• Molds are multi-cellular filaments (filamentous fungi) – reproduce by spores (these spores are exospores which are different than the endospores that you find in bacteria). Conidia – common term to refer to sperm reproduction in molds.