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Questions and Answers
What is taxonomy primarily concerned with?
Which of the following is NOT one of the three domains of life?
What method is used to determine the presence of specific bacterial enzymes?
What does the process of classification involve?
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What distinguishes a prokaryotic strain?
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Which of the following is an example of a biochemical test?
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What does morphological characteristic analysis help identify?
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Which resource provides identification schemes for identifying bacteria and archaea?
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What is the scientific name of the zombie ant fungus?
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Which fungus was mentioned as having infected a human for the first time in 2023?
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What type of reproduction is primarily used by algae?
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Which type of algae is known for producing algin, a thickener used in foods?
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What is a characteristic of diatoms?
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Which group of protists do not share a common ancestor with plants, fungi, and animals?
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Which algae type is a common cause of paralytic shellfish poisoning due to neurotoxins?
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What significant environmental factor has been associated with the increase in fungal infections?
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What distinguishes Archaea from other domains?
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What is the primary ecological role of Archaea?
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What unique capability do methanogens possess?
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How are bacteria classified based on the structure of their cell walls?
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Which of the following characteristics is true for Gram-negative bacteria?
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What type of bacteria are typically used in wastewater treatment?
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Which of the following bacteria is known for causing tissue necrosis and septicemia?
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What is an example of an endospore-forming bacterium?
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Which phylum of bacteria includes methanogenic organisms?
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What functional role do Archaea play in human health?
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Which of the following groups of microorganisms is primarily known for nutrient cycling?
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What is a common challenge associated with culturing Archaea in laboratory settings?
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Which type of bacteria undergo Gram staining to assess their cell wall structure?
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What role does Taq polymerase play in molecular biology?
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Which of the following best describes the kingdom Protista?
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What type of reproduction do fungi primarily engage in?
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Which of the following is not a feature of the kingdom Fungi?
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What is the primary role of mycorrhizae in fungi?
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Which type of hyphae contains cross-walls?
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How do dimorphic fungi exist?
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What term describes the fungal lifecycle stage consisting of two fused cells with nuclei that do not fuse?
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Which of the following is a benefit fungi provide to humans?
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Which of the following statements about Microsporidia is true?
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How do Zygomycota fungi reproduce asexually?
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Which of the following best defines mycosis?
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What is the function of lichens?
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Which group of fungi is known for forming club-shaped fruiting bodies?
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What is a primary characteristic of opportunistic mycoses?
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Study Notes
Microbial Classification
- Taxonomy is the science of classifying organisms, highlighting similarities
- Systematics, or phylogeny, studies the evolutionary history of organisms
- There are three main domains of life
- Eukarya: includes animals, plants, and fungi
- Bacteria: a diverse group of single-celled organisms
- Archaea: extremophiles, like methanogens, halophiles, and hyperthermophiles
Phylogenetic Tree
- Represents the evolutionary relationships among organisms and their shared ancestry
Taxonomic Hierarchy
- Organizes organisms into categories based on common characteristics
- These categories can be further divided into subgroups with shared traits
Classifying & Identifying Microorganisms
- Classification groups organisms into related species based on shared characteristics
- Identification matches the characteristics of an unknown organism to known organisms
- Bergey's Manual of Determinative Bacteriology provides identification schemes for bacteria and archaea
- Approved Lists of Bacterial Names lists species with established classifications
Methods for Identifying Microorganisms
- Morphological characteristics are useful for identifying eukaryotes, but don't reveal much about phylogenetic relationships.
- Differential staining techniques like Gram staining and acid-fast staining are not helpful for bacteria lacking cell walls
- Biochemical tests help determine the presence of specific bacterial enzymes
Classification of Prokaryotes
-
Prokaryotic species are populations of cells with similar characteristics
- Culture: Bacteria grown in laboratory media
- Clone: Population of cells derived from a single parent cell
- Variant: Slight genetic differences with no functional change
- Strain: Accumulated genetic differences leading to changes in behavior or properties
Classification of Viruses
- Not part of any domain; lack cellular structure; require a host cell
- Viral species are populations of viruses with similar characteristics that occupy specific ecological niches
Archaea Classification
- Distinct taxonomic grouping; lack peptidoglycan
-
Extremophiles: Thrive in extreme environments
- Halophiles: Require salt concentrations greater than 25%
- Thermophiles: Require growth temperatures above 80°C
- Methanogens: Anaerobic organisms that produce methane
Important Contributions of Archaea
- Primarily acknowledged to be beneficial rather than harmful
- Play a crucial role in global ecosystems:
- Nutrient cycling
- Wastewater treatment
- Plant immunity
- Occupy extreme environments, accessing nutrients unavailable to other organisms
Archaea and Human Health
- Can be manipulated to produce various chemicals and drugs
- Source of Taq polymerase, a key enzyme in PCR
- Compose 1.2% of the human microbiome
- Reduce skin pH, boosting defense against infection
- May produce compounds preventing cardiovascular disease
- Their ability to withstand extreme conditions makes them valuable for pharmacological processes, but also challenging to grow and culture
Bacteria Classification
- Primarily divided into two groups:
- Gram-positive: Thick peptidoglycan cell wall, staining purple
- Gram-negative: Thin peptidoglycan cell wall, with lipopolysaccharide (LPS) wall (and associated endotoxins), staining pink
- Important to note that exceptions exist, and some bacteria don't fit neatly into either group
Bacteria of Medical Importance
- Proteobacteria: Largest taxonomic group of bacteria, containing many pathogens
- Cyanobacteria: Photosynthesizing bacteria, important for ecological balance
- Bacteroidetes: Many opportunistic pathogens
- Firmicutes: Contains many pathogens
- Bacillus and Clostridium: Produce endospores
Diversity in Bacteria and Eukaryotes
- Wide range of forms and functions within both bacterial and eukaryotic domains, illustrating their vast diversity
Origin of Eukaryotes
- Endosymbiotic theory: A proto-eukaryote engulfed a proto-mitochondrion, which became an organelle, a major step in the evolution of eukaryotes
Classification of Eukaryotes
-
Protista: A catchall kingdom for diverse organisms; autotrophic and heterotrophic
- Grouped into clades based on rRNA
- Fungi: Chemoheterotrophic; unicellular or multicellular; chitin cell walls; develop from spores or hyphal fragments
- Plantae: Multicellular; cellulose cell walls; undergo photosynthesis
- Animalia: Multicellular; no cell walls; chemoheterotrophic
Kingdom Fungi
- ~100,000 documented species
-
Heterotrophic organisms: Obtain nutrients through absorption
- Saprophytic: Feed on dead matter
- Parasitic: Feed on living hosts
- The visible fruiting body, like a mushroom, is primarily for sexual reproduction
- Extensive network of mycorrhizae beneath the surface
Mycology
- The study of fungi
- Chemoheterotrophs, decomposing organic matter
- Aerobic or facultative anaerobic
Vegetative Structures of Fungi
- Vegetative structures: Not associated with reproduction
-
Molds and fleshy fungi (filamentous fungi):
- Thallus (body): Consists of hyphae filaments; a mass of hyphae is called a mycelium
- Septate hyphae: Contain cross-walls.
- Coenocytic hyphae: Lack septa.
- Vegetative hyphae: Obtain nutrients while aerial hyphae are involved in reproduction
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Yeasts: Nonfilamentous and unicellular
- Budding yeasts: Divide unevenly.
- Fission yeasts: Divide evenly.
Dimorphism in Fungi
- Dimorphic fungi can exist in both a yeast (or yeast-like) phase and a mold (filamentous) phase
Fungal Lifecycle
- Fungi reproduce sexually and asexually through the formation of spores.
- Asexual spores: Produced via mitosis and cell division; formed by the hyphae of one organism.
- Sexual spores: Result from the fusion of nuclei from two opposite mating strains, involving three phases of sexual reproduction.
Fungal Spores
- Stress-resistant cells: Can survive extreme conditions (high temperatures, UV exposure)
- Can remain dormant for years, even thousands in specific conditions.
Sexual Reproduction of Fungi
- Plasmogamy: Two cells fuse, but nuclei do NOT fuse (n+n)
- Karyogamy: Fusion of two haploid nuclei to form a diploid nucleus
- Dikaryotic hyphae: Product of plasmogamy, cells have two haploid nuclei and continue to grow, forming a mycelial network.
Largest Living Organism
- Armillaria ostoyae (Humongous Fungus) covers 2,385 acres (almost 4 square miles)
Fungal Environments
- Optimal growth at pH of 5.
- Can grow in high sugar and salt concentrations, resistant to osmotic pressure.
- Can grow in low moisture content but prefer higher levels.
- Metabolize complex carbohydrates.
- Sensitive to UV radiation.
- Most are mesophiles, growing between 25-30°C (77-86°F).
Fungi: Both Medicine and Disease
- Penicillium fungi used to produce penicillin, an antibiotic.
- Tolypocladium inflatum produces cyclosporine, an immunosuppressant used for organ transplantation.
- Fungal infections can cause meningitis, lung disease, athlete's foot, and yeast infections.
- Major contributor to food spoilage.
Fungal Influence on History
- Phytophthora infestans (fungus-like water mold) caused the Irish Potato Famine (1845-1852).
- The Salem witch trials (1692) were likely influenced by erratic behavior caused by consuming rye products with ergot fungus.
Medically Important Fungi
- Microsporidia
- Zygomycota
- Ascomycota
- Basidiomycota
Microsporidia
- No observed sexual reproduction, but likely occurs in a host.
- Lack mitochondria.
- Obligate intracellular parasites.
- Infections range from asymptomatic to symptomatic, causing diarrhea, myositis, keratitis, and bronchitis.
Zygomycota
- Conjugation fungi.
- Coenocytic hyphae.
- Asexual reproduction: Produce sporangiospores.
- Sexual reproduction: Produce zygospores, formed when nuclei of two similar cells fuse.
Ascomycota
- Sac fungi: Septate hyphae.
- Teleomorphic fungi: Produce both sexual and asexual spores.
- Anamorphic fungi: Lost the ability to reproduce sexually.
- Asexual reproduction: Produce conidiospores.
- Sexual reproduction: Produce ascospores, formed in a saclike ascus by the fusion of morphologically similar or dissimilar nuclei.
Basidiomycota
- Club fungi: Septate hyphae.
- Asexual reproduction: Produce conidiospores.
- Sexual reproduction: Produce basidiospores formed externally on a base pedestal called a basidium.
Lichens
- Mutualistic symbiosis between a green alga (or cyanobacterium) and a fungus.
- Alga produces and secretes carbohydrates; fungus provides an anchor.
- Economic importance:
- Dyes
- Antimicrobial properties (Usnea)
- Litmus
- Food for herbivores
Fungal Relationship to Humans
- Evolutionarily, fungi are more closely related to animals than plants.
- This makes drugs that kill fungi potentially dangerous to humans.
Fungal Diseases
- Mycosis: Fungal infection.
- Systemic mycoses: Deep within the body.
- Subcutaneous mycoses: Beneath the skin.
- Cutaneous mycoses: Affect hair, skin, and nails.
- Superficial mycoses: Localized (e.g., hair shafts).
- Opportunistic mycoses: Fungi harmless in their normal habitat but pathogenic in a compromised host.
Economic Benefits of Fungi
- Saccharomyces cerevisiae: Used in bread, wine, and hepatitis B vaccine production.
- Trichoderma: Produces cellulase, an enzyme used in various industries.
- Taxomyces: Produces taxol, an anticancer drug.
- Entomophaga: Used for biocontrol of insects.
- Coniothyrium minitans: Kills fungi on crops.
- Paecilomyces: Kills termites.
Zombie Ant Fungus
- Cordyceps (Ophiocordyceps unilateralis): Insect pathogen that exhibits mind control.
- Inspiration for the game "The Last of Us".
- There are pathogenic fungi that infect the zombie ant fungus.
Plant-to-Human Fungi Infection
- Chondrostereum purpureum (2023): First case of a plant fungus infecting a human.
- Infected a mycologist, causing throat irritation and hyphae growth in the neck.
- A potential sign of global warming affecting fungi.
Protists Clarification
- Protists are a group of all the eukaryotes that are not fungi, animals, or plants.
- They do not all share a common ancestor not shared with other eukaryotic groups.
Algae: Photosynthesizing Protists
- Not a taxonomic group; mixed with other groups.
- Unicellular or filamentous photoautotrophs.
- Lack roots, stems, and leaves.
- Primarily aquatic; water is necessary for growth and reproduction.
- All reproduce asexually.
- Multicellular algae can fragment or reproduce sexually through alternation of generations.
Selected Phyla of Algae
- Brown algae (kelp): Cellulose and alginic acid cell walls; multicellular and macroscopic; produce algin, a thickening agent used in food.
- Red algae: Branched thalli; mostly multicellular; harvested for agar and carrageenan; some produce a deadly toxin.
- Green algae: Cellulose cell walls; unicellular or multicellular; chlorophyll a and b; store starch; gave rise to terrestrial plants.
- Diatoms: Pectin and silica cell walls; unicellular or filamentous; store oil; produce domoic acid, causing neurological disease contracted by swimming in saltwater affected by algal blooms.
- Dinoflagellates: Cellulose in plasma membrane; unicellular; produce neurotoxins (saxitoxins) that cause paralytic shellfish poisoning; the most common cause of saltwater algal blooms.
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Description
Explore the fascinating world of microbial classification, including taxonomy, systematics, and the three domains of life: Eukarya, Bacteria, and Archaea. Understand the phylogenetic tree and taxonomic hierarchy that organize organisms based on shared characteristics. This quiz will test your knowledge on classifying and identifying microorganisms.
