2. 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
4. 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
6. 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.”
7. 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”
8. 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
9. 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
10. Ribosomes
• proteins and RNA
• prokaryotic ribosomes are smaller than
eukaryotic ribosomes
• protein synthesis
• “granular”
appearance
11. Cell Membrane and Cell Wall
• Readings question three:
What is the difference between the cell
membrane and the cell wall?
12. 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
13. Cytoplasm
• Readings question four:
• What is the cytoplasm of prokaryotic cells?
• primary structures: nucleoid and ribosomes
• plasmids: extrachromosomal pieces of DNA
15. 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
16. Clostridium tetani
• deep wound punctures that become anoxic
• tetanus toxin spreads and causes disease
• spastic paralysis and can result in death
17. Clostridium botulinum
• botulinum toxin in improperly preserved foods
• botulism can result in death due to respiratory
failure as a result of muscle paralysis
18. Clostrideium perfringens
• most prevalent reported cause of food
poisoning
• enterotoxins in the intestines
• diarrhea and intestinal cramps with no fever
or vomiting
19. 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
20. 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
21. Gram-staining
• Readings question five:
• What is the purpose of gram-staining? What
are the characteristics of gram-positive
bacteria and gram-negative bacteria?
29. Temperatures
• Minimum: “temperature below which
bacterial growth will not take place”
• Optimum: “temperature at which organisms
grow best”
• Maximum: “temperature above which
bacterial growth will not take place”
30. • What are the embalming implications
associated with the temperature preference of
bacteria?
31. pH
• Readings question four:
Describe the pH scale.
Acidophiles: bacteria that are remarkably
tolerant of acidity
32. Light
• Cyanobacteria: oxygen producing prokaryotes
– thrive in the presence of light
• Yeasts and Molds
– prefer dark areas
• Some bacteria are destroyed by ultraviolet
light.
33. Osmotic Pressure
• “pressure that develops when two solutions of
different concentrations are separated by a
semi-permeable membrane”
• microorganisms require water for growth and
are made up of 80-90% water
• high osmotic pressure removes necessary
water from a cell
• plasmolysis
• hypertonic solutions
34. Moisture
• maximum, optimum and minimum
requirement for all microorganisms
• Pathogenic bacteria are usually found in the
body’s tissues
• Fungal diseases are usually found on the body
surface.
35. Chemical Requirements
• Readings question two:
Describe the differences between autotrophic
bacteria and heterotrophic bacteria.
36. Heterotrophic Bacteria
• 3 categories:
– 1) strict (obligate) saprophyte
– 2) strict (obligate) parasite
– 3) facultative bacteria:
• Facultative saprophyte: “prefers live organic matter as a
source of nutrition but can adapt to the use of dead
organic matter under certain conditions”
• Facultative parasite: capable of living and growing with
the nutrients that its host provides
37. Carbon
• one of the most important requirements for
microbial growth
• structural backbone of living matter
• needed for all the organic compounds that
make up a living cell
• ½ of the “dry weight” of a bacterial cell is
carbon
38. Nitrogen, Sulfur, and Phosphorus
• needed by microorganisms for the synthesis of
cellular material
• e.g. protein, DNA, RNA, ATP
40. Oxygen
• Microbes that use molecular oxygen (aerobes)
produce more energy from nutrients than
microbes that do not use oxygen (anaerobes)
• Reading question two:
Describe the difference between obligate
aerobes and obligate anaerobes.
41. Microaerophilic Organisms
• “a microorganism that requires very little free
oxygen”
• only grow in oxygen concentrations that are
lower than those in air
• require about 2 – 10% free oxygen
42. Facultative Organisms
• Facultative Aerobes: “a microorganism that
prefers an environment devoid of oxygen but
has adapted so that it can live and grow in the
presence of oxygen”
• Facultative Anaerobes: “a microorganism that
prefers an oxygen environment but is capable
of living and growing in its absence”
– E.g. Bacillus anthracis, Corneybacterium
diphtheriae, Escherichia coli
44. Microbial Associations
• normal flora (microbiota)
• transient microbiota
• symbiotic relationship: “organisms live in close
nutritional relationships; required by one or
both members”
– distinguished by the degree to which the host
organism is harmed
45. Mutualism
• “a symbiotic relationship in which organisms
of two different species live in close
association to the mutual benefit of each”
– e.g. E. coli in the human digestive tract
46. Commensalism
• “the symbiotic relationship of two organisms
of different species in which one gains some
benefit such as protection or nourishment and
the other is not harmed or benefited”
– e.g. bacteria on skin surface; microorganisms
within the digestive tract
47. Parasitism
• “an interactive relationship between two
organisms in which one is harmed and the
other benefits”
• many disease-causing bacteria are parasites
• typically the host is macroscopic and the
parasite is microscopic
• roundworms and flatworms are parasites that
are large multi-cellular organisms
49. Antagonism
• “mutual opposition or contrary action. The
inhibition of one microorganism by another.”
• Involves competition among microbes
• normal microbiota protect the host against
colonization by potentially pathogenic
microbes
• normal flora produce substances harmful to
the invading microbes (pH, oxygen)
