Protozoa and Microscopic Fungi Quiz

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Questions and Answers

What is a common characteristic of protozoa?

They reproduce only asexually.

They are primarily autotrophic.

They are mobile and use endocytosis for food intake. (correct)

They have specialized tissues.

Which of the following organisms is responsible for malaria?

Plasmodium falciparum (correct)

Giardia lamblia

Entamoeba histolytica

Leishmania donovani

What is the primary component of fungal cell walls?

Peptidoglycan

Keratin

Cellulose

Chitin (correct)

How do fungi typically obtain their nutrients?

By absorbing organic matter solutions Signup and view all the answers

Which feature distinguishes microalgae from protozoa?

Microalgae are predominantly autotrophic. Signup and view all the answers

What is a known effect of pathogenic fungi?

They can produce mycotoxins that cause poisoning. Signup and view all the answers

Which organism is known for being a yeast used in bread production?

Saccharomyces cerevisiae Signup and view all the answers

What characterizes protists such as protozoa and algae?

They are all eukaryotic and can be unicellular. Signup and view all the answers

What is one factor that helps classify bacteria based on their metabolism?

Respiratory type Signup and view all the answers

Which classification method focuses on similarities and differences in characteristics between organism pairs?

Numerical taxonomy Signup and view all the answers

What type of taxonomic classification depends on the organisms' response to antibiotics?

Antibiotypic classification Signup and view all the answers

What is commonly used to compare the similarity of characteristics between two bacterial strains?

Jaccard coefficient Signup and view all the answers

How many characters should ideally be compared for a reliable classification in numerical taxonomy?

At least 50 Signup and view all the answers

Which type of taxonomy emerged with the advent of molecular biology in the 1990s?

Molecular taxonomy Signup and view all the answers

What type of classification categorizes bacteria based on their antigenic properties?

Serotype classification Signup and view all the answers

What does the presence of more than 80% similarity indicate in numerical taxonomy?

Same species Signup and view all the answers

What role do algae play in the ecosystem?

They play a significant role in the carbon cycle and biogeochemical cycles. Signup and view all the answers

Which group of algae is specifically known for containing red algae?

Rhodophytes Signup and view all the answers

What characterizes viruses in terms of their biological classification?

They can only reproduce inside living cells and have no metabolic activities outside. Signup and view all the answers

Which statement is true regarding prions?

They are infectious particles that consist only of protein and no nucleic acid. Signup and view all the answers

What is a significant cause of recent algal blooms?

Increased nutrient discharges like nitrogen and phosphate. Signup and view all the answers

How do viruses differ from living organisms?

Viruses lack cellular structures and cannot reproduce independently. Signup and view all the answers

What type of organism can be infected by viruses?

Every organism, including other viruses, can potentially be infected. Signup and view all the answers

Why are algal blooms considered a threat to seafood consumption?

They accumulate toxic compounds through the food chain. Signup and view all the answers

What does the subspecies rank notation 'subsp.' indicate?

It specifies a classification below species. Signup and view all the answers

Which of the following correctly describes the binomial nomenclature format for bacteria?

The genus name is capitalized and italicized while the species name is not. Signup and view all the answers

What is the purpose of the term 'Candidatus' in bacterial nomenclature?

To identify a bacterium lacking sufficient information for an official description. Signup and view all the answers

Which statement about the classification of Escherichia coli is true?

It is classified under the phylum Proteobacteria. Signup and view all the answers

How are the common names for bacteria determined?

They are often based on the bacteria’s habitat or function. Signup and view all the answers

In the context of bacterial classification, what does 'spp.' signify?

It denotes several species from the same genus. Signup and view all the answers

What characteristic is NOT typically used to classify bacteria?

Geographical distribution. Signup and view all the answers

Which of the following statements about taxonomic ranks is correct?

Subspecies is a rank below species. Signup and view all the answers

What does Chargaff's rules state about the ratios of nucleotides in DNA?

The amounts of purines and pyrimidines are equal. Signup and view all the answers

What is the significance of a GC% value calculated with the formula GC% = [(G+C)/G+C+A+T] X 100?

It helps to characterize species based on their nucleotide ratios. Signup and view all the answers

What is required for two strains to be considered as belonging to the same species in terms of DNA/DNA hybridization?

The hybridization rate must be greater than or equal to 70%. Signup and view all the answers

What does a 16S rRNA nucleotide identity of greater than or equal to 95% indicate?

The samples may belong to the same genus. Signup and view all the answers

Which of the following statements is true regarding two bacteria with identical GC% values?

They can be genetically distant. Signup and view all the answers

What is the primary purpose of using MALDI-TOF mass spectrometry in bacterial identification?

To analyze the total protein profile of bacteria. Signup and view all the answers

How can ribosomal RNA (rRNA) be beneficial in microbial identification?

It has a well-conserved structure in all living organisms. Signup and view all the answers

Which of the following must be true for two microbial species with the same nucleotide sequences?

They necessarily have the same GC%. Signup and view all the answers

Study Notes

Protozoa

Protozoa are eukaryotic, single-celled organisms, lacking specialized tissues.
They obtain nutrition by ingesting organic compounds.
They move using pseudopodia, flagella, or cilia.
They range in size from 1 to 700 μm, although some amoebae can reach up to 5 mm.
They have no cell walls, so their plasma membrane interacts directly with the external environment.
They live in diverse environments, such as water, soil, and even within organisms (like the lung mucus, intestines, and rumen of animals).
They can exist as free-living entities or parasites.
Protozoa reproduce using asexual or sexual methods, and some use both.
Examples include: Leishmania donovani (visceral leishmaniasis), Entamoeba histolytica (diarrhea), Trypanosoma (sleeping sickness), Trichomonas vaginalis (urogenital infection), Giardia lamblia (diarrhea), Plasmodium falciparum (malaria), and Toxoplasma gondii (toxoplasmosis).

Microscopic Fungi (or Mycetes)

Fungi are eukaryotic organisms with cell walls composed primarily of chitin.
Their internal structure resembles animal cells, including a plasma membrane, nucleus, cytoplasm, and organelles.
Unicellular fungi, known as yeasts, range in size from 10 to 50 μm.
The most common multicellular fungi are molds.
Fungi reproduce through the formation of spores, either sexually or asexually.
They derive nutrition by absorbing organic matter from their surroundings, including soil, seawater, freshwater, and host organisms.
Pathogenic fungi can cause poisoning by producing mycotoxins that affect the liver, kidneys, nerves, and skin.
They release allergenic molecules, and some species produce lytic enzymes.
Examples include Saccharomyces cerevisiae (used in bread and beer production), Candida albicans (responsible for mycosis), Penicillium (used to produce penicillin), and Aspergilus flavus (secretes aflatoxins in poorly stored cereals).

Microscopic Algae (Microalgae or Microphytes)

Algae are eukaryotic organisms, similar to higher plants, capable of using light as an energy source.
They are autotrophic, meaning they produce organic matter from mineral elements through photosynthesis using pigments, primarily chlorophyll.
Their cell walls, like plant cell walls, are composed of cellulose.
Algae inhabit freshwater, saltwater, soil, and are sometimes associated with plants.
They play a crucial role in the carbon cycle and the biogeochemical cycles of lakes and oceans.
Some algae are mobile, while others are stationary.
Their diverse colors arise from different combinations of pigments.
Algae reproduce using complex methods, including vegetative and sexual reproduction.
There are different groups of algae: chlorophytes (including green algae), euglenophytes, pyrrophytes, chrysophytes (or golden algae), pheophytes (including brown algae), rhodophytes (including red algae), and Xanthophyta (or yellow-green algae).
Algal blooms have become more frequent in recent decades, driven by climate change (warmer water) and human activities that accelerate their growth, such as nitrogen or phosphate discharges and reduced biodiversity.
Although only 2% of these compounds are recognized as toxic to animals and humans, algal blooms threaten seafood consumption, particularly bivalve mollusks (which filter and accumulate toxins) and fish (which bioaccumulate toxins through the food chain).

Viruses

Viruses are acellular and visible only under an electron microscope.
Their size varies widely but is typically between 20 to 300 nanometers (nm).
Viruses are structurally simple, consisting of a nucleocapsid.
They have genetic material (DNA or RNA) enclosed within a protein capsid, which may be covered by a lipid membrane called the envelope.
Viruses are not considered living organisms due to their lack of cellular structure, metabolism, and growth.
Viruses can replicate only by utilizing the machinery and energy of a living cell.
This makes them obligatory intracellular parasites; they are inert outside of a living cell.
Every organism can be infected by one or more viruses.
Some viruses can even infect other viruses.
Examples include: Lyssavirus (rabies virus), Coronavirus.

Prions

Prions are protein-based pathogens that, unlike viruses, bacteria, fungi, and parasites, do not contain nucleic acid (DNA or RNA) as their genetic material.
They are infectious agents.
Prion proteins can cause serious neurological diseases.

Nomenclature of Bacteria

Bacteria have a binomial nomenclature system.
The full name includes a genus name and species name.
The genus name starts with a capital letter, while the species name does not.
The genus name precedes the species name.
Bacterial names are written in Latin and italics (e.g., Escherichia coli, Staphylococcus aureus).

Identification of Bacteria

Bacterial classification relies on various observations and studies.
They can be classified based on:
- Microscopic morphology (shape and arrangement)
- Macroscopic morphology (colony appearance)
- Mobility (movement)
- Spore presence
- Gram staining results
- Growth temperature
- Respiratory type
- Nutritional requirements
- Ability to use specific carbon and nitrogen sources
- Biochemical characteristics (biotypes or biovars)
- Morphological characteristics (morphovar)
- Antigenic characteristics (serotypes or serovars)
- Pathogenic characteristics (pathotypes or pathovars)
- Enzymatic characteristics (zymotypes or zymovars)
- Sensitivity to antibiotics (antibiotypes)
- Sensitivity to bacteriophages (phageotypes, phageovars, or phagovars)

Numerical or Adansonian Taxonomy

This approach compares various characteristics (morphological, physiological, and genetic) between strains.
Selected characters are quantified numerically using binary quantification (0 or 1 for absence or presence).
The similarity coefficient characterizes the taxa, and a dendrogram illustrates the relationships.

Molecular Taxonomy

This method utilizes molecular biology techniques to study ‘non-cultivable’ organisms.
Enzymatic DNA amplification (PCR) allows access to bacterial gene sequences without the need for cultivation.
Identification relies on comparisons of nucleic acid sequences (DNA, RNA) or protein profiles.

Chargaff's Rules (GC%)

In DNA, purine content equals pyrimidine content ((A+G) / (C+T) = 1). Additionally, adenine (A) equals thymine (T) (A/T = 1), and guanine (G) equals cytosine (C) (G/C = 1).
The ratio (A+T)/(C+G) varies greatly and is specific to each species.
This coefficient, referred to as Chargaff's rules, can be determined following sequencing.
Two bacteria belonging to the same species have identical GC% (within 2.5%).
Bacteria with different GC% do not belong to the same genetic group.
Identical GC% does not guarantee identical nucleotide sequences, implying genetic distance.
Two bacterial species with the same nucleotide sequences necessarily have the same GC%.

DNA/DNA Hybridization

This method compares the entire genomes of two bacteria by measuring the degree of homology between their DNAs.
The degree of homology represents the percentage of complementary sequences relative to the total sequences.
Two strains belong to the same species only if their DNA hybridization rate (renaturation) is greater than or equal to 70%.

Nucleic Acid Sequencing

Ribosomal RNAs (rRNAs) are present in prokaryotic and eukaryotic cells, and have a largely conserved structure across all living organisms.
Specific regions of rRNA have identical sequences in all living organisms.
They are abundant, easy to purify and sequence using reverse transcriptase.
Research on 16S rRNA has differentiated Eubacteria from Archaea.
For 16S rRNA, nucleotide identity greater than or equal to 95% is required for the genus level, and greater than or equal to 98.7% for the species level.

Methods Based on Proteomic Techniques

Proteomic tools complement traditional genomics-based bacterial identification techniques.
MALDI-TOF (matrix-assisted laser desorption ionization-time of flight) mass spectrometry identifies bacteria by analyzing their total protein profiles.

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Description

Test your knowledge on protozoa and fungi, two essential groups of eukaryotic microorganisms. Explore their characteristics, reproduction methods, and examples of important species. This quiz covers both free-living and parasitic forms, as well as their roles in various environments.