Microbiology Chapter 4

Plasmids contribution to disease

Plasmids are extra DNA that are able to duplicate themselves. They encode information for resistance to antibodies or production of toxins. Plasmids can be exchanged between bacteria.

Cell wall role in protection from osmotic changes in environment

Isotonic solution: medium in which the overall concentration of solutes equals theta found inside the cell (water leaves and enters cell at same rate, creating equilibrium) Hypotonic solution: outside the cell is a medium whose concentration of solutes is lower than the inside of the cell (water enters cell) Hypertonic solution: is a medium having a higher concentration of solutes than that inside the cell (water leaves cell)

Atypical Cell Wall: Mycobacterium

Outer membrane contains a thick wax called mycolic acid ID by Acid-Fast Stain Clinical significance: Tuberculosis, and leprosy

Endospores

A resistant, asexual spore that develops inside some bacteria cells. Dormant and can withstand extreme environmental conditions (like radiation, freezing, heat, etc.), which causes the cell to be very stable because of this. They form when certain conditions change within cell (like nutrient depletion or lack of moisture). They are located with in a certain area in vegetative cells. Only seen in Gram - (+) and there are 2 genera: 1.) Bacillus - aerobic soil organism -Anthrax, Livestock pathogens, Bioweapon 2.) Clostridium - anaerobic soil bacteria (forms spores when exposed to oxygen) - gas gangrene, tetanus, botulism The endospore will remain dormant until it senses the return of more favorable conditions.

Identify the features which all cells (prokaryotes, archaea, and eukaryotes) have in common.

All cells have a plasma membrane, use ATP for energy, and store genetic information in molecules as DNA.

Describe the chemical structure of the bacterial cell wall using the terms peptidoglycan, N- acetylglucosamine (NAG) and N-acetylmuramic acid (NAM) and peptide side chains and cross- links.

Bacteria cell wall contains peptidoglycan (2 sugar components, short peptide chains), which wraps around the cell continuously. NAG & NAM connect to create peptidoglycan. Short peptide chains are made up of amino acids (side-chain amino acid and cross-bridge amino acid) that connect the peptidoglycan columns (creating cross-links).

Slime Layer contribution to disease

Bacteria that are covered in this slime layer are protected from dehydration and loss of nutrients. They also are the anchor for biofilms.

Capsules contribution to disease

Completely surround the bacteria cell, which protects the cell (like armor). -Interfering with phagocytosis -Capsule provides virulence to disease fighting cells

Why are eukaryotes larger than bacteria and archaea cells?

Eukaryotes are bigger b/c they hold so much more than prokaryotes and archaea do. They have the cytoskeleton (prevents cell from collapsing) and compartmentalized organelles.

Eukaryotic vs. Prokaryotic cell

Eukaryotes contain: -cytoskeleton -mitochondria -chloroplast

External structures of bacteria

Fimbriae: can occur at the poles of the cell or distributed evenly over the entire cell. Tend to attach to each other and other surfaces. Involved in forming biofilms (multi species communities of bacteria held together by slime layers) and other aggregations on surfaces (like rocks or glass). Pili: normally longer than fimbriae and number only one or two per cell. Involved in motility and DNA transfer (like conjugation "sex" pili). 2 types of Glycocalyx (sugar/protein layer outside cell wall): 1.) Capsule - firmly attached, organized. 2.) Slime layer - loosely attached, unorganized. Flagella: long filamentous appendages that propel bacteria.

Flagella contribution to disease

Flagella cause the bacteria cell to move from one area to another (ex. propelling from the urethra to the bladder in E. Coli)

Endosymbiotic Theory

Free-living bacteria were engulfed by another cell, resulting with new metabolic capabilities for the host cell. Eventually, the relationship became permanent and the engulfed cells became mitochondria and chloroplasts. Mitochondrial and chloroplast DNA share similarities with bacteria which still exist today Flagellum: Eukaryotes - made of microtubules (extension of cytoskeleton), covered by membrane, whipping motion Prokaryotes - made of protein called flagellin, anchored into membrane (but not covered by it), rotational motion These differences between flagellum indicate the evolution of the flagella (Convergent Evolution)

Explain (specifically) how antibiotics of the penicillin family kill bacteria without harming human cells. Explain how the antibacterial substance lysozyme kills bacterial cells and where lysozyme is found.

Human cells do not have cell walls. Bacteria have cell walls that contain peptidoglycan, which have these connecting links. Penicillin: prevents cross-bridges ---> causing cell to burst Lysozome: clips cross-bridges ---> cell wall weakens (body's natural response)

LPS (Gram-negative) contribution to disease

Lipid A (part of LPS) is responsible for infectious symptoms such as fever, dilation of blood vessels, shock, and blood clotting

Flagella

Made up of 3 components. Filament: long, outermost region (contains globular protein flagellin that is arranged in several chains that intertwine to form a helix around a hollow core) Hook: wide, filament attaches to it (consists of different protein) Basal Body: cements the flagellum to the cell wall and membrane Basal body rotates, causing the cell to move. Run: when a cell moves in one direction for a length of time Tumble: runs are interrupted by tumbles, which is when there is a random, abrupt change in direction which is caused by a reversal of flagellar rotation. Taxis: movement of bacteria moving away or towards a particular stimuli Chemotaxis: chemical stimuli Phototaxis: light stimuli

Gram-positive cell wall

Multiple peptidoglycan layers = thick Teichoic acids: primarily alcohol (like glycerol or ribitol) and phosphate. 2 types of teichoic acids: lipoteichoic & wall teichoic acids. Lipoteichoic acids: spans the peptidoglycan layer and attaches to the plasma membrane. Wall teichoic acids: linked to the peptidoglycan layer. Space between cell wall and plasma membrane is the plasmic space (contains granular layer, which is composed of lipoteichoic acid)

Atypical Cell Wall: Mycoplasmas

No cell walls Must live inside a host cell Atypical pneumonia

Describe the structure of a phospholipid molecule and identify the hydrophilic and hydrophobic portions. Explain & diagram the structure of biological membranes including the terms phospholipid bilayer, hydrophilic heads, hydrophobic tails, integral & peripheral proteins, glycoproteins, and glycolipids.

Phospholipid molecule: head (hydrophilic, water-loving), 2 fatty0acid tails (hydrophobic, water-fearing) Phospholipid bilayer: Heads pointing outward (where water is) while tales point inward (where water is not in). This creates the bilayer, which is strong and flexible, but maintains no energy. Within in bilayer are other molecules such as glycoproteins (proteins attached to carbohydrates), glycolipids (lipids attached to carbohydrates), integral proteins (embedded into the bilayer), peripheral proteins (proteins that do not interact with the tails of the layer, they are bound to the membrane indirectly)

Pili contribution to disease

Pili help move the bacteria cell and transfer DNA from one cell to another, which can add a new function to the recipient cell (like antibiotic resistance)

Transport Across the Membrane

Selective Permeability: Passive Transport: Movement of substances with the concentration gradient (high concentration to low concentration, cells don't need energy) Active Transport: Movement of substances against the concentration gradient (low concentration to high concentration, requires cell to use energy) Simple Diffusion: the overall movement of molecules or ions from an area of high concentration to low concentration Facilitated Diffusion: integral membrane proteins function as channels or carriers that facilitate the movement of ions or large molecules across the plasma membrane

Archaea

Single-celled microorganisms that live in extreme environments (like the Great Salt Lake) Structure: -unique lipids in their membrane -unique cell components -flagella similar to bacteria -lack peptidoglycan in cell walls -unique RNA polymerase and ribosomes, but similar to eukaryotes -plasmid membranes with lipid compositions not seen in any other lifeforms Archaea possess genes and several metabolic pathways that are more closely related to eukaryotes

Gram-negative cell wall

Single-layer of peptidoglycan = thin Outer membrane Periplasm Lipopolysaccharide (LPS): also called endotoxins. Responsible for many of the symptoms of Gram-negative infection Lipid A: lipid portion of the LPS and is embedded in the top layer of the outer membrane Core polysaccharide: attached to lipid A and contains unique sugars. It plays a structural role. O polysaccharide: extends outward from the core polysaccharide and is made up of sugar molecules. Functions as an antigen and is useful for distinguishing species of gram-negative bacteria.

Describe the internal structures of bacteria: cytoplasm, nucleoid region, chromosome, ribosomes, plasmids, and inclusions/granules

The internal structures of bacteria include: cytoplasm (jelly-like substance filling the interior of the cell), ribosomes (70s), plasma membrane, cell wall (containing peptidoglycan), nucleoid region (not truly membrane bound), chromosome (1 single DNA molecule, circular, attached to membrane), inclusion granules (storage of materials), plasmids (how bacteria cells replicate)

Fimbriae contribution to disease

These attach to other surfaces, sometimes forming biofilms (multi species held together by a slime layer)