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Questions and Answers
Which sample is not typically used in clinical microbiology to identify microorganisms?
Which sample is not typically used in clinical microbiology to identify microorganisms?
What does a positive catalase test indicate about an unknown bacterium?
What does a positive catalase test indicate about an unknown bacterium?
Which organism is NOT included in the mnemonic for catalase positive organisms?
Which organism is NOT included in the mnemonic for catalase positive organisms?
What is the outcome of the catalase reaction represented by the equation 2H2O2 -> 2H2O + O2?
What is the outcome of the catalase reaction represented by the equation 2H2O2 -> 2H2O + O2?
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Which of the following methods is used in genotypic identification of microorganisms?
Which of the following methods is used in genotypic identification of microorganisms?
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What is a common habitat for many bacteria?
What is a common habitat for many bacteria?
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What term is used to describe bacteria that live in and on the bodies of humans and animals without causing harm?
What term is used to describe bacteria that live in and on the bodies of humans and animals without causing harm?
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Which of the following statements about our resident bacterial flora is accurate?
Which of the following statements about our resident bacterial flora is accurate?
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What can happen under certain conditions with resident bacterial flora?
What can happen under certain conditions with resident bacterial flora?
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What is the estimated ratio of bacteria to human cells in an average 70kg human?
What is the estimated ratio of bacteria to human cells in an average 70kg human?
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Which of the following can be a consequence of resident flora turning pathogenic?
Which of the following can be a consequence of resident flora turning pathogenic?
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What is the name of the last universal common ancestor referenced?
What is the name of the last universal common ancestor referenced?
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How many identified phyla of bacteria exist, according to the content?
How many identified phyla of bacteria exist, according to the content?
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What is the primary purpose of Gram staining in microbiology?
What is the primary purpose of Gram staining in microbiology?
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Which group of bacteria is characterized by thick peptidoglycan layers in their cell walls?
Which group of bacteria is characterized by thick peptidoglycan layers in their cell walls?
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What defines the difference between phenotypic and genotypic methods of bacterial identification?
What defines the difference between phenotypic and genotypic methods of bacterial identification?
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Which of the following bacteria is classified as a Gram-negative bacillus?
Which of the following bacteria is classified as a Gram-negative bacillus?
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Which disease is associated with a spirochete?
Which disease is associated with a spirochete?
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Which type of bacteria tends to be more resistant to antibiotics due to their cell wall structure?
Which type of bacteria tends to be more resistant to antibiotics due to their cell wall structure?
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What is the role of a microbiology laboratory concerning infections?
What is the role of a microbiology laboratory concerning infections?
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What is the significance of differentiating between Gram-positive and Gram-negative bacteria?
What is the significance of differentiating between Gram-positive and Gram-negative bacteria?
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Which of the following methods is a phenotypic method of identification?
Which of the following methods is a phenotypic method of identification?
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Which of these groups includes Gram-negative bacilli?
Which of these groups includes Gram-negative bacilli?
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What type of method does Pulsed-Field Gel Electrophoresis (PFGE) represent?
What type of method does Pulsed-Field Gel Electrophoresis (PFGE) represent?
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Which characteristics are primarily used to differentiate between Gram-positive and Gram-negative bacteria?
Which characteristics are primarily used to differentiate between Gram-positive and Gram-negative bacteria?
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Which of the following pairs contains only Gram-positive cocci?
Which of the following pairs contains only Gram-positive cocci?
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What technique would be best suited for analyzing plasmid polymorphism?
What technique would be best suited for analyzing plasmid polymorphism?
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Which bacterial group is incorrectly matched with its Gram classification?
Which bacterial group is incorrectly matched with its Gram classification?
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Which process is part of genotypic methods for microbial classification?
Which process is part of genotypic methods for microbial classification?
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Study Notes
Microorganisms
- Microorganisms are diverse and include bacteria, fungi, algae, protozoa, microscopic plants, and animals.
- Single-celled microorganisms were the first forms of life on Earth, approximately 3 billion to 4 billion years ago.
- Bacteria are some of the best-studied microorganisms.
- Bacteria live in various environments, including soil, seawater, and deep within the Earth's crust.
- Bacteria have been reported to live in radioactive waste.
Bacteria Phyla
- At least 84 phyla of bacteria have been identified, but many remain uncultured.
- Only a few key organisms or lineages are shown in each domain in the phylogenetic tree.
- Branch lengths are arbitrary, and nodes collapsed to reflect phylogenetic uncertainty.
Bacteria and the Human Body
- Many bacteria reside on and within the human body without causing harm, constituting the resident flora or microbiome.
- The human body contains at least as many bacteria in its resident flora as cells in the body.
- An average human weighing 70 kg has approximately 30 trillion cells and 39 trillion bacteria.
- Resident flora can be beneficial, aiding in digestion and preventing the growth of harmful bacteria.
- Under certain conditions, resident bacteria can cause disease by producing toxins, invading tissues, triggering inflammation, or increasing cancer risk.
Bacterial Infections
- Gram-positive and Gram-negative bacteria require different antibiotic treatments.
- Gram staining classifies bacteria based on their cell wall structures.
- Four primary bacterial groups: Gram-positive cocci, Gram-positive bacilli, Gram-negative cocci, and Gram-negative bacilli.
Microbiology Laboratory Tasks
- Identifying microorganisms involved in infections is a fundamental task in microbiology labs.
- Understanding the etiopathogenic nature, clinical evolution, and appropriate antimicrobial therapy is crucial.
Identification and Typing Methods
- Traditional identification relied on phenotypic methods, but genotypic methods have emerged as reliable alternatives in recent decades.
Phenotypic Identification
- Combines various methods, including staining and cell morphology.
- Requires samples from the site of infection (feces, urine, pharyngeal exudate, etc.).
- Involves isolating and growing the microorganism.
- Compares phenotypic characteristics of unknown bacteria to known standards.
- The catalase test differentiates between Staphylococcus (catalase positive) and Streptococcus (catalase negative).
Genotypic (Molecular) Identification
- Advancements in molecular methods have revolutionized the diagnosis of bacteria and viruses.
- Methods include ribosomal RNA detection, hybridization, DNA probe, and nucleic acid amplification (PCR).
Phenotypic vs Genotypic Identification Methods
- Phenotypic methods: biochemical reactions (Gram staining), serological reactions, antimicrobial susceptibility, phage susceptibility, bacteriocin susceptibility, and cell protein profile.
- Genotypic methods: hybridization, plasmid profile analysis, restriction enzyme digestion, pulsed-field gel electrophoresis (PFGE), ribotyping, polymerase chain reaction (PCR) and variants, and ligase chain reaction (LCR).
The Three Domains
- Bacteria, Archaea, and Eukarya are the three domains of life, vital for understanding life's origin.
Gram-Positive vs Gram-Negative Bacteria
- Bacteria are classified as Gram-positive or Gram-negative based on their cell wall structure.
- This classification is crucial for selecting appropriate antibiotic treatment.
Important Groups of Bacteria
- Gram-positive cocci: Staphylococcus, Streptococcus, Enterococcus, Peptococcus, Peptostreptococcus, Viridans,
- Gram-positive bacilli: Corynebacterium, Bacillus, Clostridium, Actinomyces, Listeria, Lactobacilli, Nocardia
- Gram-negative cocci: Neisseria, Moraxella, Veillonella
- Gram-negative bacilli: Escherichia coli, Klebsiella, Proteus, Shigella, Salmonella, Vibrio, Yersinia, Haemophilus, Bordetella, Legionella, Francisella, Pasteurella, Aeromonas, Pseudomonas, Acinetobacter, Bacteroides, Fusobacterium, Campylobacter, Helicobacter pylori
- Gram-negative cocco-bacilli: Mycobacterium tuberculosis
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Description
Explore the fascinating world of microorganisms, including their various types such as bacteria, fungi, and algae. Learn about their historical significance, diversity, and the crucial roles they play in both the environment and the human body. This quiz will test your understanding of microbial life and its importance.
