Microbiology Classification Quiz

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Questions and Answers

Which of the following organisms are NOT classified as microbes?

  • Fungi
  • Viruses
  • Plants (correct)
  • Bacteria

All bacteria are harmful to humans.

False (B)

What is the main characteristic that distinguishes bacteria from other microbes?

Bacteria are prokaryotic organisms, meaning they lack a true nucleus and other membrane-bound organelles.

Fungi are ______ organisms, meaning they obtain their nutrients from other organisms.

<p>heterotrophic</p> Signup and view all the answers

Which of the following is a characteristic of bacteria?

<p>Presence of a cell wall made of peptidoglycan (B)</p> Signup and view all the answers

Match the following types of microbes with their general characteristics:

<p>Bacteria = Prokaryotic, single-celled organisms with a rigid cell wall Fungi = Eukaryotic, heterotrophic organisms with a rigid cell wall Algae = Eukaryotic, photosynthetic organisms with a cell wall Viruses = Non-living entities that require a host to replicate</p> Signup and view all the answers

Which of these characteristics is NOT common to both Gram-positive and Gram-negative bacteria?

<p>Presence of an outer membrane (C)</p> Signup and view all the answers

Viruses can reproduce independently of a host cell.

<p>False (B)</p> Signup and view all the answers

What is the primary function of teichoic acids in Gram-positive bacteria?

<p>Teichoic acids are important for maintaining cell wall integrity and contributing to the negative charge of the cell surface.</p> Signup and view all the answers

The ______ is a space located between the inner and outer membranes of Gram-negative bacteria.

<p>periplasmic space</p> Signup and view all the answers

Match the following components of the bacterial cell wall with their corresponding layer:

<p>Peptidoglycan = Thick layer in Gram-positive bacteria, thin layer in Gram-negative bacteria Teichoic acids = Present in Gram-positive bacteria, absent in Gram-negative bacteria Lipoprotein layer = Connects the peptidoglycan to the outer membrane in Gram-negative bacteria Outer membrane = Present only in Gram-negative bacteria</p> Signup and view all the answers

Which of these is NOT a beneficial function of microbes?

<p>Causing disease (D)</p> Signup and view all the answers

All protozoa are parasitic.

<p>False (B)</p> Signup and view all the answers

What are virulence factors, and how do they contribute to pathogenicity?

<p>Virulence factors are traits or mechanisms that enable pathogenic microbes to cause disease. They can help microbes evade host defenses, invade tissues, or damage host cells.</p> Signup and view all the answers

Flashcards

Microbiology

The study of microscopic organisms like bacteria and viruses.

Bacteria

Microscopic single-celled organisms found in diverse environments.

Characteristics of Bacteria

Double-stranded DNA, small free ribosomes, no membrane-bound organelles.

Fungi

Non-motile eukaryotes with rigid cell walls, heterotrophic, most are filamentous.

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Fungal Infections

Occur when host immune defenses are weakened; only a few species are pathogens.

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Algae

Simple plants, including microalgae and macroalgae, that perform photosynthesis.

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Microalgae

Tiny algae that can photosynthesize and include cyanobacteria.

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Autotrophic Growth

Photosynthesis process used by most microalgae to obtain nutrients.

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Characteristics of Viruses

Viruses exhibit both living (reproduce, mutate) and non-living (acellular, no metabolism) traits.

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Living Characteristics of Viruses

They reproduce only in host cells and can mutate rapidly.

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Non-Living Characteristics of Viruses

Acellular, cannot metabolize on their own, and contain either DNA or RNA.

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Protozoa

Single-celled microorganisms with a nucleus, may be free-living or parasitic.

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Pathogenic Microbes

Microbes that can cause infections or diseases, using virulence factors to evade host defenses.

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Virulence Factors

Traits of pathogenic microbes that enhance their ability to infect and evade the immune system.

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Gram-Positive Bacteria

Bacteria with a thick peptidoglycan cell wall and teichoic acids, retaining purple dye in staining.

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Gram-Negative Bacteria

Bacteria with a thin peptidoglycan layer and an outer membrane, do not retain purple stain.

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Study Notes

Microbiology Classification

  • Microbiology is the study of microscopic organisms (microbes)
  • Microbes include Bacteria, Viruses, Archaea, Algae, Fungi, and Protozoa

Types of Microorganisms: Bacteria

  • Bacteria are microscopic single-celled organisms
  • They thrive in diverse environments, including soil, oceans, and the human gut
  • Humans' relationship with bacteria is complex
  • Bacteria can be helpful, such as curdling milk into yogurt or aiding digestion
  • Bacteria can also be destructive, causing diseases

Characteristic of Bacteria

  • Bacterial DNA exists as a double-stranded loop, not within a nuclear membrane
  • Bacteria have small ribosomes in the cytoplasm, lacking an endoplasmic reticulum
  • They lack mitochondria and other membrane-enclosed organelles
  • Bacteria have a complex peptidoglycan-protein cell wall

Fungi

  • Fungi (Mycophyta) are non-motile eukaryotes with rigid cell walls and a true nucleus
  • They lack photosynthetic pigments, making them heterotrophic
  • Over 50,000 fungal species exist; about 300 are human pathogens
  • Most fungal infections stem from weakened host immune defenses

Characteristic of Fungi

  • All fungi are eukaryotic
  • Most fungi are filamentous, with some being unicellular
  • The protoplasm of hyphae or cells is surrounded by a rigid wall
  • Fungi typically reproduce both sexually and asexually
  • All fungi are achlorophyllous
  • Fungi can be free-living or form relationships with other organisms

Algae

  • Algae are simple plants, ranging from microscopic forms to large seaweeds like giant kelp
  • Algae can reach over 100 feet in length
  • Microalgae include cyanobacteria (formerly "blue-green algae"), green, brown, and red algae

General Characteristic of Algae

  • Most microalgae grow through photosynthesis, converting sunlight, CO2, and nutrients (like nitrogen and phosphorus) into energy
  • This growth method is called "autotrophic"

Viruses

  • Viruses are infectious agents with both living and non-living characteristics
  • Viruses reproduce at a high rate, but only within living host cells
  • Viruses can mutate
  • Viruses are acellular, meaning they lack cytoplasm and cellular organelles
  • Viruses do not perform metabolism on their own
  • Viruses generally contain either DNA or RNA, but never both

Protozoa

  • Protozoa are microorganisms in various sizes and forms, free-living or parasitic
  • They possess a nucleus containing chromosomes and organelles like mitochondria (though absent in some cases), endoplasmic reticulum, pseudopods, flagella, and cilia
  • Many parasitic protozoa are transmitted by arthropods, with multiplication and transformation into infectious stages occurring within the vector

Beneficial Microbes

  • Microbiome (normal flora)
  • Food source
  • Antibiotics and other chemicals
  • Bioengineering
  • Decomposers
  • Ecological balance
  • Biodegradation
  • Bioremediation

Pathogenic Microbes

  • Pathogenic microbes have abilities to cause infections or diseases in hosts
  • Virulence factors aggravate host defenses, aiding infection
  • Virulence factor characteristics determine pathogenicity

G+ and G- Bacterial Cell Wall

  • Bacteria are classified into Gram-positive and Gram-negative based on cell wall structure and staining response
  • Gram-positive cell walls have multiple layers of the plasma membrane and sometimes a capsule, with a thick peptidoglycan layer (20-80nm), composing around 90% of the dry weight. They also have teichoic acids (polysaccharides)
  • Gram-negative cell walls have a thin peptidoglycan layer (7-8nm), comprising only about 10% of the dry weight, and an outer membrane with lipopolysaccharides (LPS). A lipoprotein layer connects the peptidoglycan to the outer membrane.

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