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Questions and Answers
Which structure allows some bacteria to withstand mechanical stress?
Which structure allows some bacteria to withstand mechanical stress?
- Biofilms (correct)
- Pili
- Endospores
- Flagella
What is the correct genus name for the bacterium S. salivarius?
What is the correct genus name for the bacterium S. salivarius?
- Salivarius
- Firmicutes
- Streptococcaceae
- Streptococcus (correct)
Which of the following is associated with localized aggressive periodontitis?
Which of the following is associated with localized aggressive periodontitis?
- Porphyromonas gingivalis
- Bacteroides fragilis
- Streptococcus salivarius
- Aggregatibacter actinomycemcomitans (correct)
Which kingdom do bacteria belong to?
Which kingdom do bacteria belong to?
What is the family name of Streptococcus salivarius?
What is the family name of Streptococcus salivarius?
Which statement about species naming is correct?
Which statement about species naming is correct?
What type of bacterium is Porphyromonas gingivalis?
What type of bacterium is Porphyromonas gingivalis?
What is the major characteristic of the division Firmicutes?
What is the major characteristic of the division Firmicutes?
Which of the following is a type of mechanical stress that bacteria can resist?
Which of the following is a type of mechanical stress that bacteria can resist?
Which of the following terms describes the systematic classification of organisms?
Which of the following terms describes the systematic classification of organisms?
What characteristic allows Gram negative bacteria to appear pink under a microscope?
What characteristic allows Gram negative bacteria to appear pink under a microscope?
Which factor is required for the metabolic processes of most Gram negative bacteria?
Which factor is required for the metabolic processes of most Gram negative bacteria?
Which of the following correctly describes anaerobes?
Which of the following correctly describes anaerobes?
What significant component is characteristic of the outer layer of Gram negative bacteria?
What significant component is characteristic of the outer layer of Gram negative bacteria?
In which environment are aerobes most commonly found?
In which environment are aerobes most commonly found?
What type of disease is associated with Porphyromonas gingivalis?
What type of disease is associated with Porphyromonas gingivalis?
What type of organism requires a low oxygen environment to grow optimally?
What type of organism requires a low oxygen environment to grow optimally?
Which characteristic allows some bacteria to survive in dry conditions?
Which characteristic allows some bacteria to survive in dry conditions?
What happens to Gram negative bacteria when exposed to crystal violet stain?
What happens to Gram negative bacteria when exposed to crystal violet stain?
Which group of microorganisms prefers moderate temperatures around 30-40 degrees Celsius?
Which group of microorganisms prefers moderate temperatures around 30-40 degrees Celsius?
Which of the following does NOT describe the environmental requirements for Gram negative bacteria?
Which of the following does NOT describe the environmental requirements for Gram negative bacteria?
What do capnophiles specifically require for optimal growth?
What do capnophiles specifically require for optimal growth?
What structural characteristic distinguishes Gram-positive bacteria from Gram-negative bacteria?
What structural characteristic distinguishes Gram-positive bacteria from Gram-negative bacteria?
What is a common misconception about the structure of Gram negative bacteria?
What is a common misconception about the structure of Gram negative bacteria?
Which microorganisms are known to thrive in high salt concentrations?
Which microorganisms are known to thrive in high salt concentrations?
Which of the following statements is true about bacteria?
Which of the following statements is true about bacteria?
What is the optimal temperature for thermophiles?
What is the optimal temperature for thermophiles?
What group of microorganisms prefers acidic environments?
What group of microorganisms prefers acidic environments?
What is the primary function of bacteria?
What is the primary function of bacteria?
Which of the following bacteria is an example of a Gram-positive organism?
Which of the following bacteria is an example of a Gram-positive organism?
Which type of light can promote bacterial growth but high-intensity visible light can kill bacteria?
Which type of light can promote bacterial growth but high-intensity visible light can kill bacteria?
How is the DNA of bacteria structured?
How is the DNA of bacteria structured?
Which organisms are optimal at extremely high temperatures, typically around 90-100 degrees Celsius?
Which organisms are optimal at extremely high temperatures, typically around 90-100 degrees Celsius?
What kind of microorganisms can tolerate and live in neutral pH environments?
What kind of microorganisms can tolerate and live in neutral pH environments?
Which staining method is primarily used for Gram-positive bacteria?
Which staining method is primarily used for Gram-positive bacteria?
Which of the following is NOT a feature of bacteria?
Which of the following is NOT a feature of bacteria?
Which of the following classifications includes organisms that prefer high temperature environments?
Which of the following classifications includes organisms that prefer high temperature environments?
What typically differentiates a Gram-negative bacterium from a Gram-positive bacterium when stained?
What typically differentiates a Gram-negative bacterium from a Gram-positive bacterium when stained?
What is the main reason that Gram-positive bacteria retain the crystal violet stain during the Gram staining process?
What is the main reason that Gram-positive bacteria retain the crystal violet stain during the Gram staining process?
Which of these functions are commonly associated with bacteria?
Which of these functions are commonly associated with bacteria?
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Study Notes
Bacteria
- Small, single-celled microorganisms.
- Prokaryotic: lack membrane-bound organelles, have a single circular DNA chromosome.
- Gram-positive bacteria: have a thick peptidoglycan layer in their cell wall, retain crystal violet stain (e.g., Streptococcus mutans).
- Gram-negative bacteria: have a thin peptidoglycan layer with a thick lipopolysaccharide layer, don't retain crystal violet stain, appearing pink (e.g., Porphyromonas gingivalis).
- Gram-negative bacteria often possess endotoxins, which can contribute to inflammation.
Environmental Requirements for Bacteria
- Moisture: Required for metabolic processes. Most thrive in moist environments, but some can survive in dry conditions by forming spores.
- Oxygen:
- Anaerobes: do not need oxygen, may even be harmed by it (e.g., Porphyromonas gingivalis).
- Aerobes: require oxygen for survival.
- Microaerophiles: grow optimally in lower oxygen environments but still require some.
- Facultative anaerobes: can adapt and live within a range of different oxygen levels. (e.g., Streptococcus mutans).
- Carbon Dioxide: Capnophiles need increased CO2 to grow, but most can grow with normal atmospheric CO2 levels.
- Temperature:
- Psychrophiles: cold, optimal temperature 5-15 °C.
- Mesophiles: moderate, optimal temperature 30-40 °C.
- Thermophiles: high, optimal temperature 60-70 °C.
- Hyperthermophiles: extremely high, optimal temperature 90-100 °C.
- pH:
- Acidophiles: thrive in acidic environments.
- Neutrophiles: thrive in neutral environments.
- Alkaliphiles: thrive in alkaline environments.
- Light: High intensity visible light can kill bacteria, while low power visible and near-infrared light can promote bacterial growth.
- Osmotic effect: Halophiles grow and develop in high salt concentration areas.
- Mechanical stress: Some bacteria can withstand pressure/agitation by forming biofilms or protective structures (spores/capsules).
Classification of Bacteria
- Taxonomy: Systematic classification of organisms into groups.
- The scientific name comes from the last two ranks: Genus and species.
- Genus name is capitalized, species name is not.
- Scientific name is usually in italics.
- Example: Streptococcus salivarius (Genus: Streptococcus, Species: salivarius).
Bacteria in Dentistry
- Periodontal disease:
- Porphyromonas gingivalis: Gram-negative, anaerobic bacteria that contributes to inflammation and tissue destruction.
- Aggregatibacter actinomycetemcomitans: Gram-negative, facultative anaerobe that can cause localized aggressive periodontitis.
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