Prokaryotes versus

Eukaryotes

Cell morphology, structure,

and function

Chicken

egg

Human red

blood cell

Large

protozoan

(Euglena) Chloroplasts

Flea Typical bacteria

and archaea Diameter

of DNA

Viruses Proteins

Ribosomes

Amino

acids

Atoms

Scanning tunneling microscope

(STM) 0.01 nm–10 nm

Scanning electron microscope (SEM)

0.4 nm–1 mm

Transmission electron microscope (TEM)

0.078 nm–100 µm

Atomic force

microscope (AFM)

1 nm–10 nm

Compound light microscope (LM)

200 nm–10 mm

Unaided human eye

200 µm–

Mitochondrion

Coccus

Coccobacillus

Bacillus

Vibrio

Spirillum

Spirochete

Pleomorphic

Morphology of bacterial cells

Multicellular

Arrangements

Multicellular

Arrangements

Staining bacterial cells

Staining bacterial cells: simple stain

One dye is used: crystal violet

The Gram stain

The Gram stain is based on structural differences in the cell

walls of bacteria

One of the first steps a medical laboratory technologist

performs to identify bacterial pathogens

Gram positive (purple/blue)

Gram negative bacteria (pink)

The Ziehl-Neelsen acid-fast stain

Mycobacterium (rod shaped cells – pink/red)

Staphylococcus (cluster of cocci - blue)

Used to detect

Mycobacterium

M. tuberculosis

(tuberculosis)

M. leprae (leprosy)

Schaeffer-Fulton endospore stain of Bacillus

anthracis

Resting structures, resistant to

desiccation, heat, chemicals

Survival during adverse

environmental conditions

Sporulation: endospore

formation

Germination: return to

vegetative state

Bacillus

Clostridium Green-dyed endospores inside red-dyed

rod shaped bacteria

Endospores and medical significance

Negative stain of Klebsiella pneumoniae to detect

the capsule

Background stain

Bacterium

Capsule

Eosin, nigrosin or india ink can be used to stain the background

Crystal violet to stain bacterial cells

Flagellar stain of Proteus vulgaris

Flagella Presence

Number

Arrangement

on the cell

Help identify

pathogens

Dyes are used to build up layers on flagella to make them visible

when using an optical microscope

Streptococcus

pneumoniae causes

pneumonia and

meningitis

S. pneumoniae grown from

a blood culture

Apply your knowledge to understand ….

This arrangement is also seen in Neisseria gonorrhoeae, which causes

the sexually transmitted disease called gonorrhea

Streptococcus

pyogenes and strep

throat

A sputum smear showing

the typical arrangement

in chains of cocci

Apply your knowledge to understand …..

Sputum sample from a

patient with staphylococcal

pneumonia

Methicillin resistant Staphylococcus

aureus (MRSA)

Apply your knowledge to understand …..

Bacterial cells

Within a bacterial cell there is the cytoplasm: a fluid

component surrounded by an envelope called the plasma

membrane

Nucleoid

Bacterial chromosome

Ribosomes

Synthesis of proteins

Inclusions

Reserve of polysaccharides, lipids, nitrogen, phosphate

Plasmids (Not always present)

Extrachromosomal genetic elements

Inclusions

Nucleoid

Ribosomes

Plasmid

Figure 4.14b

The Plasma Membrane

Phospholipid bilayer

Integral proteins

Peripheral proteins

Proteins carry out several functions including transport across the

plasma membrane

Thick peptidoglycan found

on the outer side of the

plasma membrane

Gram-positive

bacteria

Thin peptidoglycan found in

the periplasmic space

Gram-negative bacteria

The cell wall provides structure, shape, and protects the cell from osmotic lysis

Cell wall of Gram positive bacteria

Peptidoglycan (also called murein): NAG, NAM

Teichoic acids

Cell wall of Gram negative bacteria

LPS (lipopolysaccharide)

Lipid A is an endotoxin

O polysaccharide functions as an antigen (E. coli O157:H7)

Atypical Cell Walls

Acid-fast cell walls

Waxy lipid (mycolic acid) bound to the peptidoglycan

Mycobacterium

Glycocalyx: Capsule or Slime layer

• Capsule: Organized and firmly attached to the cell wall

• Slime layer: Unorganized and loosely attached to the cell wall

Protects from desiccation

Confers adherence

capability

Allows pathogens to

escape or survive

phagocytosis

Sticky substance surrounding the outside of the bacterial cell

Made of polysaccharides, polypeptides, or both

Streptococcus pneumoniae, Klebsiella pneumoniae, Bacillus

anthracis

Fimbriae and Pili

Escherichia coli

Fimbriae allow

attachment

Fimbriae of E.

coli O157 enable

the bacterium to

adhere to the

lining of the small

intestine

Causing

a severe watery

diarrhea

Proteus species

are involved in

nosocomial

urinary tract

infections

Proteus vulgaris

Fimbriae

Flagella

Neisseria gonorrhoeae, the pathogen colonizes the mucous

membrane of the reproductive tract by attaching with fimbriae

Fimbriae and Pili

Pili are involved in motility

and genetic exchange in the

process of conjugation

Through conjugation bacteria

acquire new capabilities

Toxin production

Resistance to antibiotics

Flagella (locomotion)

Composed of filament, hook, and basal body, which anchors the flagellum to the cell wall/membrane(s)

Motile cells move toward or away from stimuli (taxis)

Flagellar proteins are H antigens (E. coli O157:H7)

Arrangements of bacterial flagella

Flagella allow movement, which in turn can allow escape from

host defense

Axial filaments are

flagellum-like structures

found in spirochetes

Causes the bacterial cell

to rotate like a corkscrew

(corkscrew motion)

Treponema pallidum (syphilis)

Axial filaments

Comparative analysis between prokaryotic

and eukaryotic cells

Eukaryotic cells

We are eukaryotes!!

The Nucleus

The nucleus contains almost all of the cell’s hereditary

information (DNA)

The nucleus of human cells can be the site of viral replication

Certain viruses such as HIV integrate their genome into our

DNA, becoming proviruses

The Endoplasmic reticulum (ER)

Systems of flattened

membranous sacs or tubules

(cisternae)

The rough ER (with ribosomes)

Synthesis of secretory

proteins and components of

cell membranes

The smooth ER carries out

various functions

Synthesis of lipids (steroids)

Detoxification - drugs or

alcohols

Ribosomes

Ribosomes are the intracellular site of protein synthesis

Eukaryotic ribosomes (80S) differ from those of bacteria

(70S) - though both types are made of proteins and

ribosomal RNA

Bacterial ribosomes

are the target of

antibiotics

The Golgi apparatus

Modifies, sorts, and ships proteins from the ER, including

those secreted by the cells

Produces lysosomes

The Golgi Apparatus

Lysosomes are filled

with digestive

enzymes that break

down various

molecules

Intracellular digestion

of macromolecules in

animal cells

Lysosomes are

involved in

phagocytosis

Lysosomes

Details of the figure will not be

part of the exam!

Peroxisomes

Oxidize organic substances (amino acids, fatty acids, toxic

substances such as alcohol)

Contain catalase, an enzyme that converts H2O2 (by-

product of the oxidation reactions) into H2O and O2

Mitochondria

Sites of cellular

respiration, a metabolic

process by which cells

form ATP

Mitochondria contain

DNA and ribosomes

(similar to those of

bacteria)

Mitochondria evolved

from bacteria

Plasma Membrane

“Fluid mosaic model” of the membrane

Three types of cytoskeleton

components

Microtubules

Microfilaments

Intermediate filaments

Cytoskeleton, Cilia, and Flagella

i.e., Keratin

Shigella and

actin filaments

Bordetella pertussis

and the ciliary escalator

of the respiratory tract

Cilia and flagella are

made up of microtubules

projected outward from

the cell surface

Cilia are not found in

prokaryotes

Cytoskeleton, Cilia, and Flagella

Endocytosis and Exocytosis

Endocytosis, a process by which eukaryotic cells take in the

“material” through formation of vesicles

Endocytosis includes

Phagocytosis

Pinocytosis

Exocytosis involves moving “material” out of the cell which

is also done through the formation of vesicles

Phagocytosis is a defense mechanism of our

body

Phagocytosis is a

process our body

uses against

pathogens

Many pathogens

have found ways to

escape or survive

phagocytosis

Bacteria

A human cell (blue)

engulfing a yeast cell (green)

Keep in mind that eukaryotic organisms you will study

include

Filamentous fungi

Yeasts

Protozoa

Helminths