Textbook Notes (368,089)
Canada (161,636)
Biology (657)
Chapter 2

Biology 2EE3 - chapter 2 - Bacteria.docx

9 Pages
204 Views
Unlock Document

Department
Biology
Course
BIOLOGY 2EE3
Professor
Turlough Finan
Semester
Fall

Description
Chapter 2 - Bacteria - some bacteria are very rich in iron because of membrane enclosed magnetite particles (magnetosomes) - these bacteria use the Earth's magnetic field in order to orient themselves and travel - magnetotactic bacteria prefer environments with little or no oxygen - bacteria use this ability to direct themselves towards areas which are anoxic - this process is magnetic-aerotaxis by which they find the desired oxygen concentration by moving a long a magnetic field 2.1 Morphology of bacterial cells - shape of bacterial cell caused by organization of cell wall - coccus is spherical; bacillus is rod, vibrio is curved rod, spirillum is spiral - ecoli is rod shaped; vibrio cholerae is vibrio; staphylococcus aureus is spherical; treponema pallidum is spirrilium - morphology itself is not enough to classify bacteria - ecoli are individual cells; other bacteria like bacillus anthracis or streptococcus pyogenes form long chains and physically connected after division - staphylococci usually produce irregular clumps rather than chains - some bacteria do not create regular shapes but create variable shapes called pleiopmorphic - mycoplasma genus are all pleiomorphic because they do not produce a cell wall - some bacteria can form hyphae which are branching filaments and can also produce mycelia which are 3-d networks penetrating out or into the soil surfaces; similar to fungi - cyanobacteria form trichomes are smooth unbranched chains of cells; sometimes have polysaccharide sheet coating - between the cells in both trichomes and hyphae have intercellular connections for nutrient/signalling molecules - most bacteria are 0.5 to 5 micrometers in length - some large bacteria have been found, largest is spherical thiomargarita namibiensis - epulopiscium fiehelsoni have multiple genomes found in cytoplasm and replicate within themselves - all bacteria limited in shortest size by the rna genome as that is usually 0.5 micrometers itself 2.2 Cytoplasm - cytoplasm is the aqueous environment inside bacteria and contains diverse components - nucleoid is the largest entity and contains a mass of DNA (ususally single, circular chromosome) coated with proteins and rna - gas vesicles are also found in bacteria for buoyancy; inclusion bodies for storage of polymers - no membrane surrounding the nucleoid - cations shield the negative charge of the sugar phosphate backbone which allows it to pack more tightly - topoisomerases are enzymes that allow the dna to coil upon itself (supercoiling) - other proteins like dna/rna polymerases exist in the nucleoid and proteins that control gene expression - most enzyme catalyzed metabolic reactions occur in the cytoplasm - depending on conditions some bacteria have includion bodies which allow them to store extra carbon, nitrogen and phosphorous - no membrane surrounds this body, ex. PHB is a lipid polymer used to store carbons - PHB can be 50% of dry weight (polyhydroxylalkanoates), used for plastic industry substitute - sulfur globules are stores of sulfur to be used as energy when oxidizing sulfur compounds - gas vesicles regulate buoyancy in a cell based on cell positions in water column in response to light/nutrients - photosynthetic bacteria also have carboxysomes which help convert inorganic carbon to organic carbon - magnetosomes are a membrane enclosed organelle which have magnetite; these may provide clues to bacterial evolution 2.3 The bacterial cytoskeleton - cytoskeleton provides internal framework for cell and interact with plasma/cell wall - the FtsZ protein forms the Z ring which is needed for bacterial division - this protein is related to tubulin which is building block for microtubules in eukarya - ftsz monomers polymerize to filaments that bundle to form z ring which form on the inner face of plasma membrane - z ring contracts by releasing subunits which ends up causing cell envelope to go inward until cell division is done - zring is missing but will reform from elements in the cytoplasm for the next division - MreB protein is another important cytoskeleton element - mreb is related to actin and form long helical bands underlying the plasma membrane - mreb is universal in non spherical bacteria and help to guide cell wall formation/cell elonglation -parM protein forms actin like filaments; found on certain plasmids - role of parM is to ensure that during seperation there will be one copy of the plasmid on each side of the cell Perspective 2.1 - Marvelous Magnetosomes - magnetoaxis is used to direct movement based on the earths magnetic field - magnetosomes are used to achieve this and are filled with magnetite (Fe3O4) - formed by the plasma membrane; and acts as a compass needle, organized in chains - they are organized into a chain through the mamk protein which creates actin like filaments - discovered through using gfp to fluoresce the molecule - mamj faciliates interaction between magnetosomes and the actin like filaments 2.4 The cell envelope - all the layers as a membrane in total are called the cell envelope The plasma membrane - plasma membrane is bilayer composed of amphipathic phospholipids - also called cytoplasmic membrane or cell membrane - bacterial membranes lack sterol lipids like cholesterol, but form sterol like compounds like hopanoids - hopanoids are planar molecules and thought to stabilize the plasma membrane - these molecules are abundant in soils and sediments - membranes are not fluid depends on temperature, lipid type, other molecules - membranes are not pure lipids, half composed of protein - functions of membrane are transport. energy production, sensing Permeability of the Plasma membrane to water - has differential permeability, uncharged molecules like O2/CO2 flow through freely - larger compounds that are polar or charged cross less easily - water usually is small enough to pass through even though it is polar, might use aquaporins - hypotonic if cytoplasm has higher solute concentration than external - these changes can cause cell to swell/prune but cell wall helps prevent this Nutirent transport - there are facilitated diffusion systems which allow molecules (abundant in environment) to cross without energy - active transport systems require energy and drive against a gradient - one way this is done is through symport; which occurs when one molecule travels down a gradient and takes along a molecule not travelling along its gradient, energy is released which allows the other molecule to move - antiport involves the ejection of one molecule releasing energy to allow another one in - ABC transporters (ATP binding cassette) have a nucleotide binding domain where ATP is hydrolyzed to give energy for transport - ABC transporters are made of 4 subunits, 2 hydrophobic in the membrane and 2 hydrophilic in the cytoplasm - also has a high-affinity solute binding protein which binds to substrates and brings them to the complex which increases the affinity Energy capture - cytochromes and membrane soluble electron carriers exist in the membrane which allows for the production of ATP through respiratory electron transport system and photosynthetic systems - ejection of electrons create proton gradient to create proton motile force Sensory sytems - plasma membrane sense environment around bacteria to signal cytoplasm response systems - links to gene expression to ensure proper protein production - ex. transporter system only expressed when substrate is sensed in environment Protein secretion - general secretory pathway allows for proteins to move out of the cell, identified by a signal peptide made up of hydrophobic amino acids at the amino terminal end of a protein - secB protein binds to the polypeptide which stops it from folding inside the cytoplasm - next secA takes it to the sexYEG channel and helps it move through to the periplasm where a signal peptidase removes the signal peptide and folding occurs outside the cell The bacterial cell wall - cell wall is made up of highly linked poly saccharide called peptidoglycan - helps prevent damage from osmotic pressure, mechanical forces, and shearing - cell wall also gives shape to the bacteria ; however mycoplasmas survive without cell wall - mycoplasma live inside hosts for protection, however - peptidoglycan is made up of NAM and NAG (N-acetylglucosamine and N-acetylmurmamic acid) - these sugars are linked by beta (1,4) glycosidic linkages, NAM is also attached to a short peptide chain to cross link peptidoglycan strands - peptide chains differ between bacteria and the cross linking differs as well - some bacteria have direct cross links between short peptide chains, others have a interlink peptide chain to connect the short peptide chains connected to NAM - some of the amino acids found in these chains are rarely found in proteins, some d isomers when only l isomers are used with ribosomes - peptidoglycan production starts in cytoplasm, where enzymes link NAM and UDP to a pentapeptide complex - then this complex is attached to bactoprenol, a cytoplasmic lipid carrier - NAG then attaches to NAM, then bactoprenol flips and the complex is in the periplasm now - it then links to other sugar complexes - some organisms produce lysozyme that can degrade peptidoglycan by hydrolyzing the beta 1,4 glycosidic linkage between NAM and NAG - if isotonic, bacteria can exist as protoplast, fragile form of bacteria without cell wall - if hypotonic then water may enter when it is a protoplast causing it to burst - gram negative have an extra layer which shields cell wall from lysozyme - lysozyme are found in mucus and tears for humans to control bacterial populations - lysostaphin is an enzyme found in staphlococcus simulans which degrades the intercross linking bridge (pentaglycine bridge) in s aereus - this gene has been engineered into cattle to stop aereus infection - therefore lysozyme degrades the glycosidic linkage and lysostaphin degrades the pentaglycine linkage - some antibiotics deactivate the peptidase enzymes that cross link peptidoglycan - for example, beta-lactam mimics an amino acid to trick the petidase enzyme - however, when enzymes attach trying to catalyze a peptide bond reaction, the active side is permanently bounded to and destroys the enzyme - this antibiotic works well only with growing cells as this can only affect those with growing peptidoglycan strands - lysozyme can work on any cell as it just tears apart the linkages - beta-lactamases destory these beta-lactams by hydrolyzing the C-N bond in the ring which is necessary for the substrate to bind to the enzyme - modified antibiotics were made to challenge this resistance, but bacteria evolved as well - in response, products like c
More Less

Related notes for BIOLOGY 2EE3

Log In


OR

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


OR

By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.


Submit