Microbiology Ch 4

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Prokaryote

Comes from the Greek words for prenucleus

Eukaryote

Comes from the Greek words for true nucleus

Bacillus

Shapes

Rod shaped

Coccus

Shapes

Spherical-shaped

Spiral

Shapes

Vibrio, spirillum, spirochete

Cytoplasm

Organelle

1. The thick, aqueous, elastic, semitransparent substance inside the plasma membrane

2. Eighty percent water plus proteins, carbohydrates, lipids, and ions

3. Includes DNA (nucleoid), ribosomes, and inclusions 

Cytoskeleton

Cytoplasm

Series of fibers in the cytoplasm which participate in cell division, maintaining cell shape, growth, and DNA movement. Made of microfilaments and intermediate filaments, and microtubules; gives shape and support

Cytosol

Cytoplasm

fluid portion of cytoplasm

Cytoplasmic streaming

Cytoplasm

Movement of the cytoplasm throughout a cell

Endoplasmic Reticulum

Organelle

Folded transport network

Rough ER

Endoplasmic Reticulum

Studded with ribosomes; sites of protein synthesis

Smooth ER

Endoplasmic Reticulum

No ribosomes; synthesizes cell membranes, fats, and hormones

Golgi Complex

Organelle

1. Transport organelle

2. Modifies proteins from the ER

3. Transports modified proteins via secretory vesicles to the plasma membrane

Lysosomes

Organelle

1. Vesicles formed in the Golgi complex

2. Contain digestive enzymes

Mitochondria

Organelle

1. Double membrane

2. Contain inner folds (cristae) of the inner mitochondrial 

3. membrane and fluid (matrix)

4. Involved in cellular respiration (ATP production)

5. Contain 70S ribosomes and circular DNA

6. Can reproduce on their own

Cristae

Mitochondria

Inner folds of the inner mitochondria

Matrix

Mitochondria

Membrane and fluid of mitochondria

Chloroplasts

Organelles

1. Location of photosynthesis 

2. Contain flattened membranes (thylakoids) that contain chlorophyll

3. Contain 70S ribosomes and circular DNA

Peroxisomes

Organelles

Oxidize fatty acids; destroy H2O2

Centrosomes

Organelles

1. Organizing center for the mitotic spindle

2. Plays a critical role in cell division

Pericentriolar matrix

Centrosomes

Region of protein fibers

Centrioles

Centrosomes

Cylindrical structures composed of microtubules

Vacuoles

Organelles

1. Cavities in the cell formed from the Golgi complex

2. Some formed by endocytosis

3. Bring food into cells; provide shape and storage

Nucleus

Organelles

1. Double membrane structure (nuclear envelope) that encloses the cell’s DNA

2. DNA is complexed with histone proteins to form chromatin

3. During mitosis and meiosis, chromatin condenses into chromosomes

Bacterial chromosome

Nucleoid

1. circular thread of double stranded DNA that contains the cell's genetic information

   1. Not enclosed within a nuclear envelope (membrane)

   2. No associated histone

Plasmids

Nucleoid

1. small extrachromosomal circles of DNA 

   1. 5–100 genes

   2. carry noncrucial genes (may encode antibiotic resistance, production of toxins)

   3. Replicate independently of the chromosome

   4. May be transferred to other bacteria

Inclusions

Organelles

1.  Contain reserve deposits of certain nutrients

   1. Metachromatic granules (volutin)

   2. phosphate reserves

   3. Polysaccharide granules

   4. energy reserves

   5. Lipid inclusions

   6. energy reserves

   7. Sulfur granules

   8. energy reserves

Carboxysomes

Inclusions

Contain RuBisCO enzyme for fication during photosynthesis CO2

Gas vacuoles

Inclusions

Protein-covered cylinders that maintain buoyancy

Magnetosomes

Inclusions

Iron oxide inclusions; destroy H2O2

Endospores

Organelle

1. Resting cells; produced inside certain bacterial cells when nutrients are depleted

2. Resistant to desiccation, heat, chemicals, and radiation

3. Can survive in a dormant state for thousands of years

4. A survival mechanism; not a reproductive process

5. Produced by members of the genera, Bacillus and Clostridium

Sporulation

Endospores

Endospore formation

Germination

Endospores

Endospore returns to vegetative state • Important to the food industry

Ribosomes

Organelles

1. Sites of protein synthesis

2. Made of protein and ribosomal RNA

3. Antibiotics that specifically interfere with prokaryotic ribosomal function and protein synthesis 

   1. Streptomycin

   2. Gentamicin

   3. Erythromycin

   4. Chloramphenicol

80S

Ribosomes

1. Consists of the large 60S subunit and the small 40S subunit

2. Some are membrane-bound: attached to endoplasmic reticulum

3. Others are free: in cytoplasm

70S

Ribosomes

1. In chloroplasts and mitochondria

2. 50S large + 30S small subunits

Pairs

Arrangement

Diplo (e.g. diplococci, diplobacilli)

Clusters

Arrangement

Staphylo (e.g. staphylococci)

Chains

Arrangement

Strepto (e.g. streptococci, streptobacilli)

Groups of four

Arrangement

Tetrads

Cubelike groups of eight

Arrangement

Sarcinae

Flagella

Motility

1. Filamentous appendages on cell surface; few in number

2. Propel bacteria

3. Made of protein flagellin

Filament

Flagella

Outermost region

Hook

Flagella

Attaches to filament

Basal body

Flagella

Consists of rod and pairs of rings; anchors flagellum to the cell wall and membrane

Cilia

Motility

short projections

Microtubules

1. Both seen in flagella and cilia

2. Organized as 9 pairs in a ring, plus 2 in the center (9 + 2 array)

3. Allow flagella to move in a wavelike manner

Tubulin

Protein that makes up microtubules

Archaella

Motility

1. Archaeal motility structure

2. Made of glycoproteins called archaellins

3. Anchored to the cell

4. Archaella (singular: archaellum) rotate like flagella

5. Use ATP for energy

Fimbrae

Motility

1. Hairlike appendages that allow for attachment

2. Involved in the formation of biofilms

3. Enable some bacteria to adhere to body surfaces

Pili

Motility

1. Gliding and twitching motility

2. Involved in DNA transfer from one cell to another

Passive processes

Movement of Materials across Membranes

Substances move from high concentration to low concentration; no energy expended; Movement continues until molecules are evenly distributed

Facilitated diffusion

Passive processes

Integral membrane proteins serve as channels or carriers

Osmosis

Passive processes

The net movement of water across a selectively permeable membrane from an area of higher area of lower water concentration water concentration

Osmotic pressure

Passive processes

The pressure needed to stop the movement of water across the membrane

Isotonic solution

Passive processes

Solute concentrations equal inside and outside of cell; water is at equilibrium

Hypotonic solution

Passive processes

Solute concentration is lower outside than inside the cell; water moves into cell

Hypertonic solution

Passive processes

Solute concentration is higher outside of cell than inside; water moves out of cell

Active processes

Movement of Materials across Membranes

Substances move from low concentration to high concentration; energy expended

Active transport

Active processes

Requires a transporter protein and ATP; transported substance moves against gradient (lower concentration to higher concentration)

Group translocation

Active processes

Requires a transporter protein and phosphoenolpyruvic acid (PEP); substance is altered as it crosses the membrane

Cell wall

Walls

1. Found in plant cells

2. Prevents osmotic lysis and protects the cell membrane

3. Made of peptidoglycan (in bacteria)

4. Contributes to ability to cause disease (pathogenicity)

5. Site of action of some antibiotics

6. Chemical composition of cell wall can be used to differentiate major groups of bacteria

Glycocalyx

Walls

1. Found in animal cells

2. External to the cell wall

3. Viscous and gelatinous

4. Made of polysaccharide and/or polypeptide

5. Contributes to virulence

   1. Capsules prevent phagocytosis and helps microbes adhere to body surfaces

   2. Helps form biofilms

Slime layer

Glycocalyx

Unorganized and loose

Capsule

Glycocalyx

Neatly organized and firmly attached

Peptidoglycan

Walls

1. Polymer of a repeating disaccharide in rows:

   1. N-acetylglucosamine(NAG)

   2. N-acetylmuramicacid (NAM)

2. Rows of repeating disaccharides are linked by polypeptides

3. Together, these form a lattice structure that surrounds and protects the entire cell

4. Penicillin interferes with the formation of the peptide cross

5. bridges that link the peptidoglycan rows, weakening the cell  wall

Gram-Positive Cell Walls

Walls

1. Thick peptidoglycan—many layers

2. Teichoic acids

   1. Lipoteichoic acid links cell wall to plasma membrane

   2. Wall teichoic acid link to peptidoglycan

   3. Carry a negative charge

   4. Regulate movement of cations

3. Polysaccharides and teichoic acids provide antigenic specificity

4. Two rings in basal body of flagella 

5. Some gram-positive bacteria produce exotoxins 

6. High susceptibility to penicillin

7. Disrupted by lysozyme

Gram-Negative Cell Walls

Walls

1. Thin peptidoglycan

2. Periplasmic space

   1. Periplasm between the outer membrane and the 

3. plasma membrane contains peptidoglycan

4. Outer membrane

   1. Outer membrane made of lipopolysaccharide (LPS), lipoproteins, and phospholipid

5. Protect from phagocytes, complement, and antibiotics

6. Outer membrane contains lipopolysaccharide (LPS)

7. Porins (proteins) form channels through membrane

8. Four rings in basal body of flagella

9. Produce endotoxins and exotoxins

10. Low susceptibility to penicillin

Gram-negative

Gram Staining Mechanisms

1. Alcohol dissolves outer membrane and leaves holes in peptidoglycan

2. CV-I washes out; cells are colorless– Safranin added to stain cells

Gram-positive

Gram Staining Mechanisms

1. Alcohol dehydrates peptidoglycan

2. CV-I crystals do not leave during decolorization step

Acid-fast cell walls

Atypical Cell Walls

1. Similar to gram-positive cell walls (thick peptidoglycan)

2. Waxy lipid (mycolic acid) bound to peptidoglycan

3. Stain with carbolfuchsin

4. Carbolfuchsin is not removed when rinsed with acid alcohol

Acid-fast genera

Atypical Cell Walls

1. Mycobacterium

2. Nocardi

Mycoplasmas

Atypical Cell Walls

1. Lack cell walls

2. Sterols in plasma membrane may protect cell from lysis

Archaea

Atypical Cell Walls

1. Wall-less or Walls of pseudomurein (lack NAM and D-amino acids)

Plasma (Cytoplasmic) Membrane

Atypical Cell Walls

1. Phospholipid bilayer that encloses the cytoplasm

2. Peripheral proteins on the inner or outer surface of the plasma membrane

3. Integral and transmembrane proteins penetrate the membrane

   1. Some transmembrane proteins form channels

4. Some membrane lipids and proteins have attached carbohydrates

   1. Glycoproteins

   2. Glycolipid

Fluid mosaic model

Plasma (Cytoplasmic) Membrane Structure

1. Membrane is as viscous as olive oil

2. Proteins move freely for various functions

3. Phospholipids rotate and move laterally

4. Self-sealing

Endocytosis

Plasma (Cytoplasmic) Membrane Function

Engulfment of material

Phagocytosis

Endocytosis types

Pseudopods extend and engulf particles

Pinocytosis

Endocytosis types

Membrane folds inward, bringing in fluid and dissolved substances

Receptor

Endocytosis types

Mediated endocytosis

3.5 to 4 billion years ago

When did life arose as simple prokaryotic organisms

2.5 billion years ago

When did first eukaryotes evolved

Endosymbiotic theory

1. Explains the origins of eukaryotes

   1. Larger bacterial cells engulfed smaller bacterial cells, developing the first eukaryotes

   2. Nucleus formed as infoldings of plasma membrane enclosed the chromosomes

   3. Ingested photosynthetic bacteria became chloroplasts

   4. Ingested aerobic bacteria became mitochondria

Axial Filaments

1. Also called endoflagella

2. Found in spirochetes

3. Anchored at one end of a cell

4. Rotation causes cell to move like a corkscrew