Morphology
Structure
Function

• “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

• Size
• Shape
• Arrangement

• 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

• Readings question one:
What are the three basic shapes that most bacteria exhibit?

• 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.”

• 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”

• 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

• 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

• proteins and RNA
• prokaryotic ribosomes are smaller than eukaryotic ribosomes
• protein synthesis
• “granular” appearance

• Readings question three:
What is the difference between the cell membrane and the cell wall?

• “the membrane that surrounds some bacterial cells; a loose gel-like structure that, in pathogenic bacteria, helps to protect against phagocytosis”
• glycocalyx
• slime layer

• Readings question four:
• What is the cytoplasm of prokaryotic cells?
• primary structures: nucleoid and ribosomes
• plasmids: extrachromosomal pieces of DNA

• “a thick-walled spore within a bacterium”

• 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

• deep wound punctures that become anoxic
• tetanus toxin spreads and causes disease
• spastic paralysis and can result in death

• botulinum toxin in improperly preserved foods
• botulism can result in death due to respiratory failure as a result of muscle paralysis

• most prevalent reported cause of food poisoning
• enterotoxins in the intestines
• diarrhea and intestinal cramps with no fever or vomiting

• protein structures attached to the cell surface that resemble “whip-like” appendages
• distributed in distinguishing patterns
• flagella of prokaryotic cells differ from eukaryotic cells

• 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

• Readings question five:
• What is the purpose of gram-staining? What are the characteristics of gram-positive bacteria and gram-negative bacteria?

Bacterial Growth

• “a visible group of bacteria growing on a solid medium, presumably arising from a single microorganism”

• Physical: temperature, pH, light, osmotic pressure, moisture
• Chemical: carbon, nitrogen, sulfur, phosphorus, trace elements, oxygen

• Readings question three:
What are psychrophiles, mesophiles, and thermophiles?

• Desulfofrigus oceanense (Arctic and Antarctic
Oceans)

E. coli

Fossilized Microbes from Yellowstone’s Hot Springs

• 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?

• Readings question four:
Describe the pH scale.
Acidophiles: bacteria that are remarkably tolerant of acidity

• Cyanobacteria: oxygen producing prokaryotes
– thrive in the presence of light
• Yeasts and Molds
– prefer dark areas
• Some bacteria are destroyed by ultraviolet light.

• “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

• 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.

• Readings question two:
Describe the differences between autotrophic bacteria and 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

• 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

• needed by microorganisms for the synthesis of cellular material
• e.g. protein, DNA, RNA, ATP

• iron, copper, and zinc
• essential for the function of certain enzymes

• 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.

• “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 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

• can grow in the presence or absence of oxygen
– e.g. Streptococcus pyogenes

• 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

• “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

• “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

• “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?

• “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)