Chapter 3 and 4: Prokaryotic Diversity

Eukaryotic Cells

Animals, plants, fungi, and protist

• Membrane-bound organelles; compartmentalize the cytoplasm and perform specific functions.

• Nucleus with DNA chromosomes.

Prokaryotic Cells

Monera

• No Nucleus or other membrane-bound organelles

Cytoplasm

• Fluid that fills the cell

• 70-80% water

• 3 major parts

  • Cytosol, organelles (ribosomes), inclusions.

• The “Factory area” of the cells

Prokaryotic Ribosomes

• 60% Ribosomal RNA and 40% protein

• Size 70S (S=Svedberg Unit)

• Two subunits

  • Large and small

• Site of protein synthesis

• Found in all cells

  • Vary in size and number

Inclusions and Granules

• Intracellular storage bodies

• Vary in size, number, and content.

• Used when environmental sources are depleted.

• Gas vesicles. (Buoyancy)

• Magnetosomes (Direction)

Cytoskeleton

An internal network of protein polymers that is closely associated with the cell wall.

Chromosome

Single, circular, double-stranded DNA molecule that contains all the genetic information required by a cell.

Plasmids

• Free small circular, double-stranded DNA.

• Not essential for bacterial growth and metabolism

• Used in genetic engineering.

  • Readily manipulated and transferred from cell to cell.

Endospore

Inert, resting structures produced by some Gram-positive genera.

• Clostridium, Bacillus, and Sporosarcina.

Have a 2-phase life cycle:

• Vegetative cell

• Endospore

Sporulation

Formation of endospores.

• Hardiest of all life forms.

• Withstands extreme conditions.

• Not a means or reproduction.

Germination

Return to vegetative growth

Vegetative Cells

• Sensitive to extreme temperatures and radiation

• Gram-positive

• Normal water content and enzymatic activity

• Capable of active growth and metabolism

Endospores

• Resistant to extreme temperatures and radiation

• Do not absorb gram stain, only special endospore stains.

• Dehydrated; no metabolic activity

• Dormant; no growth or metabolic activity.

Cell Evelope

• External covering outside the cytoplasm

• Composed of two basic layers:

  • Cell wall

  • Cell membrane

• Maintains cell integrity

• Two different groups of bacteria demonstrated by Gram stain.

  • Gram-positive bacteria

  • Gram-negative bacteria

Gram-Positive Bacteria

• Cell Membrane

• Cell Wall with a thick peptidoglycan layer.

• Gram-______

Gram-Negative Bacteria

• Cell Membrane

• Cell wall with a thin peptidoglycan layer

• Outer membrane

Lipopolysaccharide (LPS)

A toxin composed of Lipid A embedded in the outer membrane, a core polysaccharide, and the O side chain.

• Outer membrane of a gram-negative bacterial cell

Structure of Cell Walls

• Determines cell shape, and prevents lysis due to changing osmotic pressures.

• Peptidoglycan (aka Murein)

Peptidoglycan

Aka Murein

• Unique macromolecule composed of a framework of long glycan (NAG and NAM) chains cross-linked by short peptide fragments.

Gram-Positive Cell Wall

NAG

• N-acetylglucosamine

NAM

• N-acetylmuramic acid

Pentapeptide

tetrapeptide

Gram-negative Cell Wall

NAG

• N-acetylglucosamine

NAM

• N-acetylmuramic acid

Direct link

Cell Membrane

aka Cytoplasmic membrane, Plasma membrane.

• Phospholipid bilayer with embedded proteins.

  • Fluid mosaic model

Cell Membrane Functions

• Protection

• Selective Permeability

• Compartmentalization

• Transport of molecules

• Cell Recognition & communication.

• Providing a site for energy reactions, nutrient processing, and synthesis.

Cell Membrane Structure

• Phospholipid bilayer

• Glycoprotein

  • Carbohydrate Protein

• Glycolipid

  • Carbohydrate lipid

Glycocalyx

• Coating of molecules external to the cell wall

• Made of sugars and/or proteins

• Two types

  • Slime layer

  • Capsule

Glycocalyx Function

• Protection

• Prevent Phagocytosis

• Attachment

• Dehydration

Slime Layer

Loosely organized and attached

• Hard to phagocytosize

Capsule

Highly organized, tightly attached

Phagocytosis

a type of endocytosis in which large particles are engulfed by membrane invagination, after which the particles are enclosed in a pocket, which is pinched off from the membrane to form a vacuole.

Biofilms

NEEDS TO BE WET

• Microbes non resilient to stressors

• Collect nutrients from flowing liquids

• Nutrient exchange

• Resistant to penetration from toxic molecules.

• Genetic Exchange

Filamentous Appendages

• Two Major groups of appendages

  • Motility

    • Flagella

    • Axial filaments (periplasmic flagella)

  • Attachment or channels

    • Fimbriae

    • Pili

Flagella

Motility - 360 rotation

• Mechanism of rotation: “Run & Tumble”

• Move toward or away from stimuli (taxis)

  • attraction

  • Chemotaxis

  • Phototaxis

  • Magnetotaxis

Phototaxis

directional movement using flagella in response to light

Chemotaxis

When a chemical gradient of an attractant exists, the length of runs is extended, while the length of tumbles decreased.

Magnetotaxis

directional movement of bacterial cells using flagella in response to a magnetic field.

Monotrichous

Having a single flagellum at one end of cell, usually a bacterial cell

Amphitrichous

having two flagella or tufts of multiple flagella, with one flagellum or tuft located at each end of the bacterial cell

Lophotrichous

having a single tuft of flagella located at one end of a bacterial cell

Peritrichous

having numerous flagella covering the entire surface of a bacterial cell

Periplasmic Flagella

aka axial filaments, endoflagella or axial fibrils.

• Found in spirochetes

• A type of internal flagellum

Fimbriae

• Fine, hair-like bristles

• More numerous

• Function:

  • Adhesion/stick to surfaces and other cells

Pili

• Rigid, long, tubular structures

• Less numerous

• Sex pili:

  • Transfer of genetic material

Prokaryote Habitats and Functions

• _______ are ubiquitous

• Extremely resilient and adaptable

• Metabolically flexible

Functions:

• Capturing (“fixing”) and recycling elements.

• Cleaning up the environment.

• Cause diseases.

• Food production

• Food spoilage.

Mutualism

type of symbiosis in which two populations benefit from, and depend on, each other.

• Bacteria in human colon

Commensalism

type of symbiosis in which one population benefits and the other is not affected.

• Staphylococcus on skin

Parasitism

type of symbiosis in which one population benefits while harming the other.

• Tuberculosis bacteria in human lung.

The Gram Stain

Developed by Hans Christian Gram

• Differential Stain

  • Gram-positive stain

  • Gram-negative stain

  • Atypical Stain

• Important basis of bacterial classification and identification.

• Practical aid in diagnosing infection and guiding drug treatment.

Differential Stain

Using more than one dye

Gram-Positive Stain

Retain crystal violet and stain purple

Gram-Negative Stain

Lose crystal violet and stain red from safranin counterstain.

Atypical Stain

Neither Gram-Positive nor Gram-Negative stains

Nontypical Cell Walls

Some bacterial groups lack typical cell wall structure

• Mycobacterium and Nocardia

• Gram-Positive cell wall structure with lipid mycolic acid (cord factor)

  • Pathogenicity and high degree of resistance to certain chemicals and dyes

  • Basis for acid-fast stain

• Some bacteria have no cell wall

  • E.g Mycoplasma

  • Cell membrane is stabilized by sterols (to resist lysis)

  • Pleomorphic

Cyanobacteria

• Oxygenic Photosynthesis

• Gram-Negative

• Contain photosynthetic chlorophyll-A pigments and gas vesicles.

• Give off oxygen (use H2O as an e-donor)

• Free-Living nonpathogenic bacteria

Oxygenic Photosynthesis

type of photosynthesis found in plants, algae, and cyanobacteria, and in which H2O is used as the electron donor to replace an electron lost by a reaction center pigment, resulting in oxygen as a byproduct

Green and Purple sulfur bacteria

• Use sulfides for oxidation

• Contain photosynthetic bacteriochlorophyll pigment

• Do not give off oxygen

• Anoxygenic photosynthesis

• Free-living nonpathogenic bacteria

Green and purple non-sulfur bacteria

• Anoxygenic Photosynthesis

• Use substrates other than sulfides for oxidation

• Contain photosynthetic bacteriochlorophyll pigment

• Free-Living nonpathogenic bacteria

Anoxygenic Photosynthesis

type of photosynthesis found in many photosynthetic bacteria, including the purple and green bacteria, where an electron donor other than H2O is used to replace an electron lost by a reaction center pigment, resulting no oxygen production

Rickettsia

• Tiny, gram-negative bacteria

• Most are pathogens

• transmitted by arthropods

  • E.g. Rickettsia rickettsii

    • Rocky Mountain spotted fever.

• Obligate intracellular parasites

Chylamdias

• Tiny, gram-negative coccobacillus

• Not transmitted by arthropods

  • Chlamydia trachomatis

    • Severe eye infection (trachoma) and one of the most common sexually transmitted diseases

  • Chlamydia Pneumoniae

    • Lung infections

Archaea

• Some are extremophiles.

• Adapted to heat, salt, acid pH, pressure, and atmosphere.

• Includes: methane producers, hyperthermophiles, extreme halophiles, and sulfur reducers.

• Constitute third Domain ______

• Contain unique genetic sequences in there rRNA

• Have unique membrane lipids and cell walls

Extremophiles

Live in the most extreme habitats in nature

Bacteria cell wall

• Peptidoglycan, or none.

Archaea cell wall

• Pseudopeptidoglycan, or

• glycopeptide, or

• Protein (s-layer), or

• none

Bacteria motility structure

Rigid spiral flagella composed of flagellin

Archaea motility structure

Rigid spiral flagella composed of archaeal flagellins

Bacteria Ribosomes

70S

Archaea Ribosomes

70S

• Structure similar to 80S