12. Prokaryotic Cells
• Comparing Prokaryotic and Eukaryotic
Cells
– Prokaryote comes from the Greek words
for prenucleus.
– Eukaryote comes from the Greek words
for true nucleus.
13. Prokaryote Eukaryote
• One circular • Paired
chromosome, not in chromosomes, in
a membrane nuclear membrane
• No histones • Histones
• No organelles • Organelles
• Peptidoglycan cell • Polysaccharide cell
walls walls
• Binary fission • Mitotic spindle
14. Glycocalyx
• Outside cell wall
• Usually sticky
• A capsule is neatly
organized
• A slime layer is
unorganized & loose
• Extracellular
polysaccharide
allows cell to attach
• Capsules prevent
phagocytosis
19. Gram-Positive cell walls
• Teichoic acids:
– Lipoteichoic acid links to plasma membrane
– Wall teichoic acid links to peptidoglycan
• May regulate movement of cations
• Polysaccharides provide antigenic variation
20. Gram-Negative Outer Membrane
• Lipopolysaccharides, lipoproteins, phospholipids.
• Forms the periplasm between the outer membrane and
the plasma membrane.
• Protection from phagocytes, complement, antibiotics.
• O polysaccharide antigen, e.g., E. coli O157:H7.
• Lipid A is an endotoxin.
• Porins (proteins) form channels through membrane
22. Gram Stain Mechanism
• Crystal violet-iodine crystals form in cell
• Gram-positive
– Alcohol dehydrates peptidoglycan
– CV-I crystals do not leave
• Gram-negative
– Alcohol dissolves outer membrane and leaves holes
in peptidoglycan
– CV-I washes out
23. Atypical Cell Walls
• Mycoplasmas
– Lack cell walls
– Sterols in plasma membrane
• Archaea
– Wall-less, or
– Walls of pseudomurein (lack NAM and D amino acids)
24. Damage to Cell Walls
• Lysozyme digests disaccharide in peptidoglycan.
• Penicillin inhibits peptide bridges in peptidoglycan.
• Protoplast is a wall-less cell.
• Spheroplast is a wall-less Gram-positive cell.
• L forms are wall-less cells that swell into irregular
shapes.
• Protoplasts and spheroplasts are susceptible to
osmotic lysis.
25. Fimbriae & Pili
• Fimbriae allow
attachment
• Pili are used to
transfer DNA from
one cell to another
Fimbriae
200 nm
26. Flagella
• Outside cell wall
• Made of chains of
flagellin
• Attached to a protein
hook
• Anchored to the wall
and membrane by
the basal body
29. Motile Cells
• Rotate flagella to run or tumble
• Move toward or away from stimuli (taxis)
• Flagella proteins are H antigens
(e.g., E. coli O157:H7)
33. Fluid Mosaic Model
• Membrane is as viscous as olive oil.
• Proteins move to function
• Phospholipids rotate and move
laterally
34. • Some prokaryotes
– Do have specialized membranes that perform
metabolic functions
0.2 m 1 m
Respiratory
membrane
Thylakoid
membranes
(a) Aerobic prokaryote (b) Photosynthetic prokaryote
35. Nucleoid
• The typical prokaryotic genome
– Is a ring of DNA that is not surrounded by a
membrane and that is located in a nucleoid region
• Some species of bacteria
– Also have smaller rings of DNA called plasmids
Chromosome
1 m
36. Endospores
• Resting cells
• Resistant to desiccation, heat, chemicals
• Bacillus, Clostridium
• Sporulation: Endospore formation
• Germination: Return to vegetative state
42. Type of Bacteria: Nutrition and metabolic adaptation
• A great diversity of nutritional and metabolic
adaptations have evolved in prokaryotes
• Examples of all four models of nutrition are found
among prokaryotes
– Photoautotrophy
– Chemoautotrophy
– Photoheterotrophy
– Chemoheterotrophy
43. Type of Bacteria: Nutrition and metabolic adaptation
• Major nutritional modes in prokaryotes
44. Type of Bacteria: Metabolic Relationships to Oxygen
• Obligate aerobes
– Require oxygen
• Facultative anaerobes
– Can survive with or without oxygen
• Obligate anaerobes
– Are poisoned by oxygen
57. Classification: Subkingdom Archaebacteria
Crenarchaeota (Thermophile & Acidophile)
P. furiosus (archaea)
• In the marine sand surrounding
sulfurous volcanoes.
• Optimally at 100 C (212 F)
• Highly resistant to radiation
• May possess an efficient
system for repairing DNA.
60. Classification: Subkingdom Eubacteria
Clamydias
• Chlamydia trachomatis
- May be transmitted to newborn's eyes
- Painful urination and watery discharge
• Mycoplasma hominis
• Ureaplasma urealyticum
61. Nongonococcal Urethritis
• Chlamydia trachomatis
– May be transmitted to newborn's eyes
– Painful urination and watery discharge
• Mycoplasma hominis
• Ureaplasma urealyticum
62. Gonorrhea
• Neisseria gonorrhoeae
• Attaches to oral or urogenital mucosa by fimbriae
• Females may be asymptomatic; males have painful
urination and pus discharge
• Treatment with antibiotics
• Untreated may result in
– Endocarditis
– Meningitis
– Arthritis
– Ophthalmia neonatorum
68. Classification
Blue green algae (Cya
I. Cyanophyta
Morphology
• Non nuclear membrane
• Cell wall ; Cellulose & Pectin
• Non flagella
• Cyanophycean Starch
• Pigment : chlorophyll a , B - carotene , F
phycobilin 2 type ; c - phycoer
69. I. Cyanophyta
Habitat
•
• phycoplankton
• Ex. Anabaena , Nostoc , Calothrix , Cylin
Oscillatoria etc.
• Mutualism ; lichen :-
• Gloeocapsa & Nostoc is phycobionts
• Anabaena azollae & Azolla filiculoides
• Blue green algae Protozoa rhiz
70. I. Cyanophyta
Reproduction
• Only asexual reproduction
• Binary fission : Chroococcus , An
• Fragmentation : Oscillatoria
• Akinete : gl
KNO3 & NH4Cl
:
• Heterocyst : N2
Anabaena , Nostoc , O
