Microbiology Chapter 4- Prokaryotes

1. DNA not enclosed w/in a membrane. Singular circularly arranged chromosome. 2. NOT associated with histones 3. Lack membrane-enclosed organelles 4. Cell walls almost always have complex polysaccharide peptidoglycan 5. Binary fission. (DNA copies, split into two)

1. DNA is in nucleus and in multiple chromosomes. Separated from cytoplasm by a nuclear membrane. 2. DNA associated with proteins- Histones and Non-histones. 3. Membrane-enclosed organelles: Mitochondria, ER, Golgi Complex, Lysosomes and Chloroplasts. 4. If cell walls= simple! 5. Mitosis

0.2-2.0 micrometers -diameter 2-8 micrometers- length

Coccus: spherical Bacillus: rod-shaped Spiral

Round

divide!

Pairs= diplococci Patterns= streptococci Groups of 4= tetrads Groups of 8= sarcinae Clusters= staphylococci

single rods

Appear in pairs after division

Occur in chains

Oval, look very similar to coci

1. Bacterial shape 2. Specific genus

Bacteria that look like curved rods

Helical shape. Rigid bodies. Propeller-like external appandages (Flagella)

Helical AND Flexible Move by axial fillaments (resemble flagella but are internal)

1. Stella: star-shaped 2. Haloarcula: rectangular, flat 3. Triangular

Heredity

maintain a single shape.

True!

Can have many shapes

1. Structures external to the cell wall 2. The cell walll 3. Structures internal to the cell wall

Glycocalyx Flagella Axial Fillaments Pili Fimbriae

-Substance secreted by prokaryotes on the surface. -General term used for substances that surround cells - is viscous (sticky) -Gelatinous polymer -Composed of polysaccharide OR polypeptide OR both -Made inside the cell then secreted out

-the substance is organized and firmly attached to the cell wall

Negative staining

-it is unorganized and loosely attached to cell wall

-bacterial virulence -pathogenic bacteria from phagocytosis by the cells of the host

Biofilms

Glycocalyx that helps cells in a biofilm attach to their target environment and to each other. -protects cells within it -facilitates communication between the cells -enables cell survival by attaching to various surfaces

Dehydration and viscosity can prevent the nutrients from leaving the cell

-long, filamentous appendages that propel bacteria

Atrichous

1. Peritichous: distributed over the entire cell 2. Polar: @ one or both poles/ends of cells

1. Monotrichous: single flagellum @ one pole 2. Lophotrichous: a tuft of flagella from one pole 3. Amphitichous: Flagella @ both poles

1. Filament 2. Hook 3. Basal Body

-long, outermost region -constant in diameter -contains globular protien flagella in chains that intertwine/form a helix around hollow core -not covered by membrane/sheath -attached to slightly wider HOOK

-anchors flagellum to the cell wall and plasma membrane -composed of a small central rod inserted in a series of rings

-2 pairs of rings 1. outer pair anchored to portions of cell wall 2. inner pair anchored to plasma membrane

Only inner pair is present

Rotation from the basal body. **Rotation is either clockwise or counterclockwise

-Speed and Direction -Motility

-Ability of an organism to move by itself -Enables bacterium to move toward a favorable environment or away from bad.

"Run" or "Swim"

"Tumbles"

Reversal of flagella rotation

The movement of bacterium toward/away from particular stimulus

1.Chemotaxis: chemicals 2. Phototaxis: light

Oxygen Ribose Galactose

1. Positive Chemotactic Signal= "Attractant"- move toward stimulus with many runs, few tumbles 2. Negative Chemotactic Signal= "Repellent"- frequency of tumbles increases as bacteria move away

Flagellar protein. Useful for distinguishing among serovars- variations within a species of gram-negative bacteria.

-Anchored at one end of spirochete -structure similar to flagella -movement similar to corkscrew: enables bacterium to move more effectively through bodily fluids

-unique structure and motility -move by axial fillaments or endoflagella -bundles fibrils @ ends of the cell beneath an outer sheath/spiral around the cell

Gram Negative

-Can occur @ poles or evenly distributed over entire surface of cell -# from 2-hundreds per cell -adhere to each other/surfaces -involved in forming biofilms -help bacteria adhere to epithelial surfaces in body

-longer than fimbriae -small # in cell -involved in motility and DNA transfer (twitching and gliding motility) -used to bring bacteria together to allow DNA transfer (conjugation) = Conjugation Pili

Pili extend by addition of subunits of pilun, make contact with surface, then retracts as subunits are dissembled. -"Gripping Hook Model": results in short, jerky movements

Smooth, gliding movement of myxobacteria. -allows microbes to travel in environments with low water content (biofilms and soil)

-Complex, semirigid structure repsonsible for shape of the cell -surrounds plasma membrane and protects it from adverse changes. -almost all prokaryotes have cell walls -helps maintain shape/serves as point of anchorage for flagella -contributes to ability of species to cause disease -site of action for antibiotics

To prevent bacterial cells from rupturing when water pressure is greater than it is outside the cell.

Peptidoglycan

-components of it are assembled in the cell wall -forms "backbone" by alternating NAM and NAH molecules in linked rows -Adjacent rows are linked by polypeptides -4 amino acids are attached to the "backbone" and alternate in D and L patterns.

Penicilin

Weakens cell wall so the cell undergoes lysis.

Destruction caused by rupture of plasma membrane and loss of cytoplasm.

-many layers of peptidoglycan- thick, rigid structure -contain teichoic acids (primary alcohols)

1.Lipoteichoic: spans peptidoglycan and is linked to plasma membrane 2. Wall Teichoic: linked to peptidoglycan layer

May bond and regulate movement of cations

-Cell growth -Preventing wall breakdown -Preventing cell lysis

-Polysaccharides -grouped into medically significant types

-Thin layer of peptidoglycan and an outer membrane -Peptidoglycan is bonded to lipoproteins in outer membrane -also in the periplasm (gel-like fluid b/w outer and plasma membrane) -do not contain Teichoic Acids -Low amounts of Peptidoglycan = high susceptibility to mechanical breakage

Lipopolysaccharides (LPS)

-Strong (-) charge = ability to evade phagocytosis -provides barrier to certain antibiotics (penicillin), digestive enzymes (lysozome), detergents, heavy metals, bile salts and some dyes.

Porins: proteins that form channels and permit the passage of molecules (nucleotides. disaccharides, peptides, amino acids, vitamin B12 and Fe)

-large complex molecule -3 components: 1. Lipid A 2. Core polysaccharide 3. O polysaccharide

-Lipid portion of LPS -embedded in top layer of outer membrane -released by gram-negative bacteria when they die (functions as an endotoxin) -repsonsible for symptoms associated with infections by gram negative bacteria (fever, shock, etc)

-Attached to Lipid A, contains unusual sugars -structural role = to provide stability

-extends outward from core p. -composed of sugar molecules -functions as an antigen -useful for distinguishing species of gram-negative bacteria

Differences in the structure of the cell walls of Gram +/- and how they react to the reagents

Crystal Violet

Crystals to form

Dehydrates the peptidoglycan, making it impermeable to the c.violet-iodine

Dissolves the outer membrance and leaves holes in peptidoglycan layer. -C. violet-iodine layer diffuses

-No walls or very little material

-lack walls or have walls that contain polysaccharides/proteins -NOT peptidoglycan

-Chemicals in cell wall usually prevent harm -Can be damaged by exposure to Lysozyme

-digestive enzyme -occurs naturally in some eukaryotic cells - in TEARS, mucus and saliva -active on the major cell wall components of most Gram + bacteria **Catalyzes hydrolysis of the bonds b/w the sugars in the repeating disaccharide "backbone" or peptidoglycan -completely destroys gram + wall

Protoplast

L Forms

-may form spontaneously or in repsonse to penicillin -can live/divide repeatedly

-wall is not destroyed to same extent as + -Part of outer membrane remains

Spheroplast

Osmotic Lysis

-thin structure lying inside the cell wall and enclosing the cytoplasm -consists primarily of phospholipids -e- micrographs- look like 2-layered structures -phospholipid molecules are arranged in 2 parallel rows = lipid bilayer

Serve as a selective barrier through which materials enter/exit the cell **Selective permeability

1. Passive Processes 2. Osmosis

Net movement of molecules/ions from high concen. to low concen. until ions/molecules are evenly distributed -Cell does NOT expend energy ***Equillibrium

Proteins function as channels/carriers that facilitate movement of ions across membranes. -Cell does NOT expend energy -Uses transporters

-Net movement of solvent molecules across a selectively permeable membrane. High to low concen. -Chief Solvent = Water!

Pressure required to prevent movement of pure water into a solution containing some solutes

1. isotonic 2. hypotonic 3. hypertonic

-overall concentration of solutes = that inside the cell -water leaves/enters @ same rate -Cells contents are in equillibrium with sol'n outside the cell wall

-Concentration of Solutes < inside -most bacteria live in hypotonic sol'ns -cell wall resists further osmosis and protects from lysis

-higher concentration of solutes than inside -Most bacteria in this sol'n shrink or plassmolyze b/c water leaves the cell by osmosis

-Active Transport -the cell uses energy in the form of ATP to move substances across membrane

-substance of the cell inside plasma membrane - ~80% water -Primarily proteins, carbs, lipids, inorganic ions & low-molec weight carbons -thick, aqueous, semitransparent, elastic -major structures: nucleoid, ribosomes, reserve deopsits -protein filaments -LACK cytoskeleton & cytoplasmic streaming

-Site of protein synthesis -2 subunits consisting of protein and rRNA -smaller/less dense than euk. -70S -some antibiotics work by inhibiting protein synthesis on prok. ribosomes

80S

Svedleberg Units. -indicate the relative rate of sedimentation during ultra high speed centrifugation.

-Metachromatic Granules -Polysaccharide Granules -Lipid -Sulfur Granules -Carboxysomes -Gas Vacuoles -Magnetosomes

Reserve deposits within the cytoplasm

-large inclusions -sometimes stain red with blue dyes -known as volutin collectively -found in algae, fungi, protozoa, bacteria

-consist of glycogen and Starch -presence is demonstrated when iodine is applied to the cells - granules appear reddish brown (glycogen) and blue (starch) with iodine

-revealed by staining cells with fat soluble dyes (sudan)

-derive energy by oxidizing sulfur/sulfur- containing compounds -serve as energy reserve

-contain enzyme ribulose 1,5 diphosphate carboxylase -in nitrifying bacteria, cyanobacteria, thiobacilli

-hollow cavities -maintain buoyancy

-inclusions of Fe3O4 (Iron Oxide) -formed by several gram- negative bacteria -may protect cell against hydrogen peroxide accumulation

-specialized "resting" cells formed by gram + bacteria when essential nutrients are depleted. -highly durable dehydrated cells with thick walls and additonal layers -found internal to bacterial cell membrane -can survive extreme heat, lack of water and exposure to toxic chemicals/radiaton in environment -** 1 per cell

Process of endospore formation within a vegetative cell -begins when a key nutrient becomes scarce/unavailable

-Process by which endospores return to a vegetative state -can remain dormant for thousands of years