CHAPTER 2 Morphology of bacterial cells Common bacterial shapes morphologies Spherical s coccus pl cocci Rod shaped s bacillus pl bacilli Spiral s spirillum pl spirilla Comma shaped s vibrio pl vibrios Pleomorphic varied shapes One capitilized or italicized is the shape If italicized and capitalized then it is referring to the genus Diplococcus is pairs of cocci staphylococcus is grape like clusters of cocci streptococcus is chains of cocci micrococci is cubical clusters of cocci Streptobacillus is chains of rods Morphology of bacterial cells Size of bacteria can vary greatly Usually smaller than eukaryal cells bacteria are often 0 5 5 m in length SMALL eukaryal cells are usually 5 m in diameter Morphology of bacterial cells There are exceptions to the general size of bacterial cells Thiomargarita namibiensis up to 700 m in diameter Can be seen with the naked eye look like a string of pearls prokaryotic Epulopiscium fishelsoni 200 700 m x 80 m Some mycoplasma cells are only 0 2 m in diameter The cytoplasm What is in the cytoplasm of bacterial cells a ribosome is not a membrane bound organelle plasmids are extra pieces of DNA that some bacteria have that give them unique characteristics The cytoplasm DNA nucleoid largest area within cytoplasm is nucleoid region housing the chromosome s and DNA attached to the inside of the cell envelope so that when the cell divides each cell will replication machinery get a copy The cytoplasm Inclusion bodies may be present Sulfur globules energy source Gas vesicles buoyancy control for bacteria that are photosynthetic or aerobic so they need to be towards the top of the water in the pond caboxysomes location of carbon fixation reactions Poly B hydroxybutyrate carbon and energy source Mnetosomes magnetite to find low oxygen areas because they do not like oxygen The bacterial cytoskeleton What kinds of internal structures help to organize bacterial cells orient bacteria within geomagnetic field help them sink down proteins that assist in keeping everything in or moving it to the correct not as well developed in prokaryotes as it is in eukaryotes Some cytoskeleton proteins are involved in cell wall synthesis during cell division FtsZ Cyoskeleton locations in cells and MreB FtsZ will create a z ring where the cell is about to divide MreB forms a ring inside the cell just under the cell envelope giving the cell it s shape rod shaped organisms have this but spherical shapes have this The cell envelope What are the critical structural functional properties of the bacterial cell envelope The cell envelope typically consists of plasma cytoplasmic membrane cell wall and sometimes an additional outer membrane The cell envelope Cytoplasmic Plasma membrane PM separates interior of the cell from external environment Composed of a phospholipid bilayer with embedded proteins May have sterol molecules called hopanoids to help with stability across temperature ranges The cell envelope How do items cross the PM and get into a cell O2 CO2 are small and can diffuse across H2O is helped across by aquaporin protein channels flow of water across the PM toward the side with a higher solute omosis concentration Osmosis can cause a cell to swell or shrivel but a strong cell wall can help keep a bacterial cell alive during these hardships hypertonic higher solute concentration outside of the cell so water moves out the cell will shrivel this prevents bacteria from reproducing isotonic solute concentration is equal on both side of the membrane hypotonic higher solute concentration inside the cell so water moves in causing the cell to swell Red blood cells do not have a cell wall so they will burst but plant and animal cells have cell walls which prevent them from bursting Facilitated diffusion using a protein channel to move particles WITH a concentration The cell envelope How do nutrients cross the PM gradient The cell envelope How do nutrients cross the PM concentration gradient Active transport using energy in the form of ATP to move particles against a Co transport mechanisms symport antiport symport move in the same direction antiport move in the opposite directions ATP binding casette ABC transporters something is too large to get into cell so it will bind to a protein which will bind to the ABC transporter which will change and allow the molecule in but ATP must be used The cell envelope The PM can also be used for cpturing energy Embedded electron transport chains help create proton motive force used for respiration or photosynthesis used to derive energy for motion flagella The PM can hold sensory proteins detect environmental changes alter gene expression to respond to changes they are embedded in the plasma membrane The cell envelope Protein secretion making proteins and shipping them outside the cell Uses ATP energy Examples Toxins enzymes etc The cell envelope Cell wall CW composed of crosslinked strands of peptidoglycan structure is similar to a chain link fence gives cells their shape and protection from osmotic lysis bursting mechanical forces The cell envelope Peptidoglycan is made of N acetylmuramic acid NAM with a small The peptide and how its cross linked varies by species N acetlyglucosamine NAG The cell envelope Several of the amino acids found associated with NAM in peptidoglycan are unusual D forms instead of L D forms are stereoisomers mirror images of the L forms normally found in biological proteins The cell envelope How does the CW actually form The cell envelope Can the CW structure be degraded Naturally by lysozyme found in tears and saliva The cell envelope Can the CW structure be degraded Artificially by Beta lactam antibiotics These work by preventing peptidoglycan crosslinking weakening the cell wall structure The cell envelope So what happens when you weaken the CW The cell can t resist osmotic pressure changes The cell envelope What about antibiotic resistance Some bacteria can produce an enzyme beta lactamase to destroy the critical b lactam ring structure The cell envelope So the CW is critical but are all CW structures the same A stain method developed in 1884 by Hans Christian Gram can separate many microbes into one of two classes The cell envelope Gram positive cells have A thick outer layer of peptidoglycan A very narrow periplasmic space Teichoic charged The cell envelope Gram negative cells have acids embedded in the peptidoglycan to give it more structure negatively A varying width periplasmic space containing a very thin