Anatomy of Bacteria
Morphology
Structure
Function
Binary Fission
• “a method of asexual reproduction involving
halving of the nucleus and cytoplasm of the
cell followed by the development of each half
into a new individual”
• septum
• progeny cells
• generation time
Morphology
• Size
• Shape
• Arrangement
Size
• prokaryotic (bacteria) cells are very small
compared to eukaryotic cells
• prokaryotic cells are the most abundant form
of life on earth
• prokaryotic cells can survive in conditions that
are too extreme for eukaryotic cells
Shape
• Readings question one:
What are the three basic shapes that most
bacteria exhibit?
Spiral
(Vibrio, Spirillum, Spirochete)
• Vibrio: “curved or bent rods that resemble
commas”
• Spirillum: “a corkscrew shape with a rigid cell
wall and hair-like projections called flagella
that assist in movement”
• Spirochete: “a flexible cell wall but no flagella
in the traditional sense. Movement occurs by
contractions (undulating) of long filaments
(endoflagella) that run the length of the cell.”
Arrangement
• Readings question two:
What are the three basic arrangements that
most bacteria exhibit?
Additional arrangements:
Tetracocci: “grouping of four spherical shaped
cells”
Sarcinae: “a cube-like packet of eight spherica
bacteria”
Structure and Function
• up until the 1950’s prokaryotes were believed to
simply be “bags of enzymes”
• prokaryotes have a simpler construction than
eukaryotes
• prokaryotic cell has 5 essential structural
components:
–
–
–
–
–
Nucleoid (bacterial chromosome)
Ribosomes
Cell membrane
Cell wall
Capsule
Nucleoid
•
•
•
•
•
bacterial chromosome
typically one large circular molecule of DNA
floats freely in the cytoplasm
genetic control center of the cell
determines all of the properties and functions
of the bacterium
Ribosomes
• proteins and RNA
• prokaryotic ribosomes are smaller than
eukaryotic ribosomes
• protein synthesis
• “granular”
appearance
Cell Membrane and Cell Wall
• Readings question three:
What is the difference between the cell
membrane and the cell wall?
Capsule
• “the membrane that surrounds some bacterial
cells; a loose gel-like structure that, in
pathogenic bacteria, helps to protect against
phagocytosis”
• glycocalyx
• slime layer
Cytoplasm
• Readings question four:
• What is the cytoplasm of prokaryotic cells?
• primary structures: nucleoid and ribosomes
• plasmids: extrachromosomal pieces of DNA
Endospores
• “a thick-walled spore within a bacterium”
Endospores
• produced by the bacterium to help it survive
in an unfavorable environment
• formed by vegetative cells- “sporulation”
• one of the most resistant forms of life
• germination
Clostridium tetani
• deep wound punctures that become anoxic
• tetanus toxin spreads and causes disease
• spastic paralysis and can result in death
Clostridium botulinum
• botulinum toxin in improperly preserved foods
• botulism can result in death due to respiratory
failure as a result of muscle paralysis
Clostrideium perfringens
• most prevalent reported cause of food
poisoning
• enterotoxins in the intestines
• diarrhea and intestinal cramps with no fever
or vomiting
Flagella
• protein structures attached to the cell surface
that resemble “whip-like” appendages
• distributed in distinguishing patterns
• flagella of prokaryotic cells differ from
eukaryotic cells
Pili (Fimbriae)
• short, hair-like structures on the surface of
prokaryotic cells composed of protein
• shorter, thinner, and straighter than flagella
• allow bacteria to attach to surfaces
• e.g. Neisseria gonorrhoeae
Gram-staining
• Readings question five:
• What is the purpose of gram-staining? What
are the characteristics of gram-positive
bacteria and gram-negative bacteria?