Microbiology Outcome 4: Classification of Microorganisms

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Questions and Answers

What is the purpose of taxonomy?

To identify only microorganisms

To classify, describe, identify, and name all living organisms (correct)

To study the characteristics of only eukaryotes

To compare the differences between prokaryotes and eukaryotes

How many domains are there in modern phylogeny?

3 (correct)

What is a phylogenetic tree?

A diagram depicting how closely related organisms are (correct)

A chart showing the characteristics of eukaryotes

A diagram showing the life cycle of microorganisms

A graph demonstrating the growth of microorganisms

What is the main difference between prokaryotes and eukaryotes?

The presence or absence of a membrane-bound nucleus Signup and view all the answers

Why are viruses not found on phylogenetic trees?

Because they are not made up of cells Signup and view all the answers

What do the terms 'pro' and 'eu' mean in the context of prokaryotes and eukaryotes?

'Pro' means 'before' and 'eu' means 'true' Signup and view all the answers

Which of the following is a characteristic of Eukaryotic cells?

Presence of membrane-bound nuclei Signup and view all the answers

What is the main difference between Prokaryotic and Eukaryotic cells?

Prokaryotes lack membrane-bound nuclei Signup and view all the answers

What is the term for the protein coat that surrounds a virus?

Capsid Signup and view all the answers

What is the term for a dormant, highly resistant structure formed by some Bacteria?

Endospore Signup and view all the answers

What is the purpose of a capsule in Bacteria?

To protect from the host's immune system Signup and view all the answers

What is the term for the region in Prokaryotes where DNA is found?

Nucleoid Signup and view all the answers

What is a key feature of Gram-positive cell walls?

A thick layer of peptidoglycan Signup and view all the answers

What is a characteristic of Archaea?

They are extremophiles Signup and view all the answers

What is the main component of the cell wall in Gram-negative bacteria?

Peptidoglycan Signup and view all the answers

What is a characteristic of Protozoa?

They are a diverse group of eukaryotes Signup and view all the answers

What is the main difference between Archaea and Bacteria?

The composition of their cell walls Signup and view all the answers

What is a characteristic of Algae?

They are photosynthetic Signup and view all the answers

What is the primary difference between prokaryotes and eukaryotes?

Mode of nutrition Signup and view all the answers

What is the function of a virus's protein capsid?

To protect the genetic material Signup and view all the answers

What is the purpose of fixation in microscopy?

To attach the specimen to the slide Signup and view all the answers

What is the characteristic of fungi that makes them resemble animals?

Heterotrophic mode of nutrition Signup and view all the answers

What is the difference between a positive stain and a negative stain?

What absorbs the dye Signup and view all the answers

What is the name of the microscope that uses a beam of electrons to produce an image?

Electron Microscope Signup and view all the answers

What is the primary purpose of Gram staining?

To distinguish between Gram-positive and Gram-negative bacteria Signup and view all the answers

What is the name of the staining technique used to identify encapsulated yeast and bacteria?

India ink or nigrosin stain Signup and view all the answers

What is the term for the normal populations of microorganisms that inhabit the body?

Flora Signup and view all the answers

How do normal flora prevent colonization of pathogenic bacteria?

By occupying all binding sites and competing for nutrients Signup and view all the answers

What is a potential harmful effect of normal flora?

Some can be opportunistic pathogens Signup and view all the answers

What can lead to overgrowth of normal flora and secondary infection?

Dysbiosis Signup and view all the answers

Study Notes

Cell Wall Structure

Gram-positive cell walls feature a thick peptidoglycan layer with embedded teichoic acid situated outside the plasma membrane.
Gram-negative cell walls consist of three layers: an inner membrane, a thin peptidoglycan layer, and an outer membrane containing lipopolysaccharides.

Prokaryotes: Archaea

Archaea are unicellular organisms with significant genetic and metabolic differences from bacteria.
Their cell walls are composed of pseudopeptidoglycan, not peptidoglycan.
Extremophiles, Archaea can survive in extreme conditions including high temperatures, varied pH, and high salinity.

Eukaryotes: Protists

Protists form an informal grouping of eukaryotes not classified as plants, animals, or fungi.
This group includes algae, which can be unicellular or multicellular, photosynthetic, and have cellulose-based cell walls.
Protozoa, another subgroup, are diverse and often regarded as "not alive".

Classification of Microbial Organisms

Modern phylogeny identifies three main domains: Bacteria, Archaea, and Eukarya.
Prokaryotes are defined as organisms without membrane-bound nuclei; eukaryotes possess such nuclei.
Viruses are acellular and lack a cellular structure, composed of a protein capsid with either DNA or RNA, and are not classified on phylogenetic trees.

Prokaryotic vs Eukaryotic Cells

Most microbes are unicellular; bacteria typically measure about 1 μm, while viruses can be smaller.
Bacteria inhabit numerous environments, can be harmless, beneficial, or pathogenic, and possess peptidoglycan in their cell walls.
Bacterial shapes vary and they exhibit diverse metabolic capabilities, including photosynthesis.

Cell Structures of Bacteria

Key structures include nucleoid, endospores, ribosomes, capsules, fimbriae, and pili.
Bacterial staining techniques help distinguish between gram-negative and gram-positive cells, utilizing methods like Gram staining and acid-fast staining.

Normal Flora

Each area of the body harbors unique flora, comprising mixed populations of bacteria and fungi, contributing to natural immunity.
Colonization begins at birth influenced by maternal transfer, the environment, and social interactions.

Benefits of Normal Flora

Prevent colonization of pathogenic bacteria by competing for binding sites and nutrients.
Can produce antimicrobial substances and vitamins, aiding in digestion.
Stimulate lymphoid tissue development.

Harmful Effects of Normal Flora

Some normal flora can become opportunistic pathogens if overgrown, like E. coli.
Dysbiosis may lead to secondary infections.
Certain organisms like Giardia can be pathogenic.

Eukaryotic Microbes: Fungi

Fungi resemble plants in form but are heterotrophic, requiring external nutrients.
Their cell walls are made of chitin, encompassing macroscopic forms like mushrooms as well as molds and yeasts, some of which can cause diseases.

Acellular Microbes: Viruses

Viruses cannot survive independently; they require a host organism to replicate.
They can infect various organisms, including bacteria (bacteriophages), protozoa, and animals.

Microscopy Techniques

Wet mount: specimen observation in a droplet of liquid under a cover slip.
Fixation methods: heat or chemical fixing to attach specimens to slides while killing them.
Staining: procedures include positive staining (where cells absorb dye) and negative staining (where the background absorbs the stain) to enhance visualization.
Simple staining highlights specific structures within the microbes.

Taxonomy in Microbiology

Taxonomy involves classification, description, and identification of organisms based on shared characteristics.
Phylogenetic trees illustrate relationships through genetic, biochemical, and embryological comparisons, moving beyond just visible similarities.

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Description

Test your knowledge of microbial classification, taxonomy, and phylogenetic trees. Learn how microorganisms are grouped based on shared characteristics and how genetic, biochemical, and embryological comparisons are used to determine relatedness.