Transcript Anatomy of Bacteria

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:
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Nucleoid (bacterial chromosome)
Ribosomes
Cell membrane
Cell wall
Capsule
Nucleoid
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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?
Physiology of Bacteria
Bacterial Growth
Bacterial Colony
• “a visible group of bacteria growing on a solid
medium, presumably arising from a single
microorganism”
Requirements for Growth
• Physical: temperature, pH, light, osmotic
pressure, moisture
• Chemical: carbon, nitrogen, sulfur,
phosphorus, trace elements, oxygen
Temperature
• Readings question three:
What are psychrophiles, mesophiles, and
thermophiles?
Psychrophiles
• Desulfofrigus oceanense (Arctic and Antarctic
Oceans)
Mesophiles
E. coli
Thermophiles
Fossilized Microbes from Yellowstone’s Hot Springs
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”
• What are the embalming implications
associated with the temperature preference of
bacteria?
pH
• Readings question four:
Describe the pH scale.
Acidophiles: bacteria that are remarkably
tolerant of acidity
Light
• Cyanobacteria: oxygen producing prokaryotes
– thrive in the presence of light
• Yeasts and Molds
– prefer dark areas
• Some bacteria are destroyed by ultraviolet
light.
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
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.
Chemical Requirements
• Readings question two:
Describe the differences between autotrophic
bacteria and heterotrophic bacteria.
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
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
Nitrogen, Sulfur, and Phosphorus
• needed by microorganisms for the synthesis of
cellular material
• e.g. protein, DNA, RNA, ATP
Trace Elements
• iron, copper, and zinc
• essential for the function of certain enzymes
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.
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
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
Aerotolerant Organisms
• can grow in the presence or absence of
oxygen
– e.g. Streptococcus pyogenes
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
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
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
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
• Readings question five:
What is the synergistic effect?
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)