Microorganisms and Bacteria Overview

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Questions and Answers

Which sample is not typically used in clinical microbiology to identify microorganisms?

Cerebrospinal fluid

Pharyngeal exudate

Urine

Blood (correct)

What does a positive catalase test indicate about an unknown bacterium?

It is a Gram-negative bacterium.

It lacks nucleic acid amplification.

It is a Streptococcus species.

It is a Staphylococcus species. (correct)

Which organism is NOT included in the mnemonic for catalase positive organisms?

Streptococcus (correct)

Nocardia

Escherichia coli

Helicobacter

What is the outcome of the catalase reaction represented by the equation 2H2O2 -> 2H2O + O2?

Decomposition of hydrogen peroxide Signup and view all the answers

Which of the following methods is used in genotypic identification of microorganisms?

PCR Signup and view all the answers

What is a common habitat for many bacteria?

Deep within the earth's crust Signup and view all the answers

What term is used to describe bacteria that live in and on the bodies of humans and animals without causing harm?

Resident flora Signup and view all the answers

Which of the following statements about our resident bacterial flora is accurate?

They outnumber the human cells in our body. Signup and view all the answers

What can happen under certain conditions with resident bacterial flora?

They can cause disease. Signup and view all the answers

What is the estimated ratio of bacteria to human cells in an average 70kg human?

1:2 Signup and view all the answers

Which of the following can be a consequence of resident flora turning pathogenic?

They trigger inflammatory responses. Signup and view all the answers

What is the name of the last universal common ancestor referenced?

LUCA Signup and view all the answers

How many identified phyla of bacteria exist, according to the content?

84 Signup and view all the answers

What is the primary purpose of Gram staining in microbiology?

To differentiate bacteria based on their cell wall structure Signup and view all the answers

Which group of bacteria is characterized by thick peptidoglycan layers in their cell walls?

Gram-positive cocci Signup and view all the answers

What defines the difference between phenotypic and genotypic methods of bacterial identification?

Phenotypic methods involve the study of morphology and staining Signup and view all the answers

Which of the following bacteria is classified as a Gram-negative bacillus?

Vibrio cholerae Signup and view all the answers

Which disease is associated with a spirochete?

Syphilis Signup and view all the answers

Which type of bacteria tends to be more resistant to antibiotics due to their cell wall structure?

Gram-negative bacteria Signup and view all the answers

What is the role of a microbiology laboratory concerning infections?

To fully identify microorganisms and determine effective antimicrobial therapy Signup and view all the answers

What is the significance of differentiating between Gram-positive and Gram-negative bacteria?

It dictates the type of antibiotics that should be used for treatment Signup and view all the answers

Which of the following methods is a phenotypic method of identification?

Biochemical reactions Signup and view all the answers

Which of these groups includes Gram-negative bacilli?

Escherichia Signup and view all the answers

What type of method does Pulsed-Field Gel Electrophoresis (PFGE) represent?

Genotypic method Signup and view all the answers

Which characteristics are primarily used to differentiate between Gram-positive and Gram-negative bacteria?

Coloration and cell wall structure Signup and view all the answers

Which of the following pairs contains only Gram-positive cocci?

Staphylococcus, Enterococcus Signup and view all the answers

What technique would be best suited for analyzing plasmid polymorphism?

Restriction enzyme digestion Signup and view all the answers

Which bacterial group is incorrectly matched with its Gram classification?

Corynebacterium - Gram-negative Signup and view all the answers

Which process is part of genotypic methods for microbial classification?

Ligase Chain Reaction Signup and view all the answers

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.