Microbes in Biology
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Questions and Answers

What is the cell size of yeast?

  • 5–10 µm (correct)
  • 10–15 µm
  • 2–5 µm
  • 15–20 µm

    • What temperature range do most yeasts grow best at?

  • 30 – 40°C
  • 5 – 15°C
  • 10 – 20°C
  • 20 – 30°C (correct)

    • What is the main method of reproduction for molds?

  • Budding
  • Forming spores (correct)
  • Binary fission
  • Fragmentation

    • Which type of microbes can grow in both aerobic and anaerobic environments?

    <p>Facultative anaerobic</p> Signup and view all the answers

    What is destroyed by heat but resistant to dry conditions?

    <p>Fungal spores</p> Signup and view all the answers

    Which type of microorganism is classified as prokaryotic?

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

    What is the biology of small living organisms (microorganisms) relating to foods known as?

    <p>Food Microbiology</p> Signup and view all the answers

    Which microorganism is responsible for producing phycocyanin, a type of antioxidant?

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

    Which microorganism is known for producing omega-6 & omega-3 polyunsaturated fatty acids (PUFAs)?

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

    Which factor does not affect microbial growth?

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

    What is the mechanism of bacteria gram staining?

    <p>Staining with crystal violet-iodine complex</p> Signup and view all the answers

    What is the size comparison between viruses and bacteria?

    <p>10nm for viruses, 1µm for bacteria</p> Signup and view all the answers

    How do some viruses replicate?

    <p>By inserting genetic materials into host cells</p> Signup and view all the answers

    Which microalgae is known for producing Astaxanthin?

    <p>Chlorella zofingiensis</p> Signup and view all the answers

    What type of organisms are Protozoa?

    <p>Single-celled, eukaryotic organisms</p> Signup and view all the answers

    Which kingdom includes single-celled organisms living in extreme conditions, such as thermophiles?

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

    What characteristic is used to classify microorganisms?

    <p>Cell shape, size, and structure arrangement</p> Signup and view all the answers

    Which type of microorganism can be both single-celled or multi-celled and exhibit different modes of growth like photoautotrophic, heterotrophic, and mixotrophic?

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

    What type of microorganisms can cause foodborne illnesses and food spoilage?

    <p>All of the above</p> Signup and view all the answers

    How are microorganisms classified into kingdoms?

    <p>Based on specific characteristics such as cell shape, size, and structure arrangement</p> Signup and view all the answers

    Which kingdom includes single-celled organisms that often live in extreme conditions, such as thermophiles?

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

    What are examples of foodborne diseases caused by microorganisms?

    <p>Cholera, avian influenza, and ciguatera food poisoning</p> Signup and view all the answers

    How are microorganisms classified based on characteristics?

    <p>Based on their cell shape, size, and structure arrangement</p> Signup and view all the answers

    What do fungi include?

    <p>Both single-celled (yeasts) and multi-celled (molds) organisms</p> Signup and view all the answers

    How do bacteria impact daily life?

    <p>By serving as a source of drugs</p> Signup and view all the answers

    What are the six kingdoms into which microorganisms are classified?

    <p>The six kingdoms into which microorganisms are classified include Protista, Fungi, Archaebacteria, Eubacteria, Plantae, and Animalia.</p> Signup and view all the answers

    What are the characteristics used to classify microorganisms?

    <p>Microorganisms are classified based on characteristics such as cell shape, size, and structure arrangement.</p> Signup and view all the answers

    How are microorganisms detected in food?

    <p>Microorganisms can be detected in food using specific methods.</p> Signup and view all the answers

    What are the examples of foodborne diseases caused by microorganisms?

    <p>Examples of foodborne diseases caused by microorganisms include cholera, avian influenza, and ciguatera food poisoning.</p> Signup and view all the answers

    What are the different types of growth exhibited by Protista?

    <p>Protista can exhibit different modes of growth like photoautotrophic, heterotrophic, and mixotrophic.</p> Signup and view all the answers

    Explain the classification of microorganisms mentioned in the text.

    <p>The classification of microorganisms mentioned in the text includes prokaryotic microorganisms (e.g. bacteria), eukaryotic microorganisms (e.g. fungi, microalgae, protozoa), and viruses.</p> Signup and view all the answers

    What are the factors that affect microbial growth according to the text?

    <p>The factors affecting microbial growth mentioned in the text are nutrition, temperature, pH, light requirement, and the growth curve.</p> Signup and view all the answers

    Provide examples of beneficial applications of microorganisms in daily life.

    <p>Beneficial applications of microorganisms in daily life mentioned in the text include the production of foods such as beer, cheese, and soy sauce, as well as the production of nutritional foods like Spirulina cereal and Fat Choi.</p> Signup and view all the answers

    What are the nutritional supplements and antioxidants mentioned to be produced by microorganisms?

    <p>The nutritional supplements and antioxidants mentioned to be produced by microorganisms include phycocyanin produced by Spirulina, omega-6 &amp; omega-3 polyunsaturated fatty acids (PUFAs) such as Arachidonic acid (AA) produced by fungi, and Eicosapentaenoic acid (EPA) and Docosahexaenoic acid (DHA) produced by diatoms and dinoflagellates.</p> Signup and view all the answers

    Explain the production of fermented food by microorganisms as discussed in the text.

    <p>The text mentions the production of fermented foods by microorganisms, giving examples such as the production of foods through fermentation.</p> Signup and view all the answers

    Explain the characteristics of molds and their method of reproduction.

    <p>Molds contain thread-like filaments called hyphae, and when hyphae extend and form a large mass, it is called a mycelium. They reproduce by forming spores, which disperse from the parent and germinate under favorable conditions.</p> Signup and view all the answers

    Describe the growth requirements of yeasts and their importance in the food industry.

    <p>Yeasts are single-celled, eukaryotic organisms that grow best at pH 4.5 – 5 and at a temperature of 20 – 30°C. They can grow in the presence and absence of oxygen (facultative anaerobic). Yeasts are important in the food industry as starters for producing fermented foods.</p> Signup and view all the answers

    Explain the oxygen requirements of microbes and provide examples of aerobic and anaerobic growth.

    <p>Microbes that require oxygen for growth are classified as aerobic, while those inhibited by oxygen are classified as anaerobic. Facultative anaerobic microbes can grow in both aerobic and anaerobic environments. For example, Saccharomyces cerevisiae can grow aerobically in the presence of oxygen and change to anaerobic growth when oxygen is deficient.</p> Signup and view all the answers

    Discuss the role of agar plates/broth in microbial maintenance.

    <p>Agar plates/broth provide nutrients for bacterial growth, making them useful for maintaining and studying microbial cultures.</p> Signup and view all the answers

    Explain the importance of yeasts in the food industry, with a specific example.

    <p>Yeasts, such as Saccharomyces cerevisiae, are crucial in the food industry as starters for producing fermented foods. This includes the production of bread, beer, and wine.</p> Signup and view all the answers

    1. What is the mechanism of bacteria gram staining?

    <p>Bacteria gram staining involves fixed cells on a slide and staining with crystal violet-iodine complex.</p> Signup and view all the answers

    1. What is the size of viruses compared to bacteria cells?

    <p>Viruses have a size of 10nm, whereas bacteria cells have a size of 1µm.</p> Signup and view all the answers

    1. What is the main method of reproduction for green microalgae like Chlamydomonas and Chlorella?

    <p>Green microalgae like Chlamydomonas and Chlorella can reproduce asexually or sexually.</p> Signup and view all the answers

    1. What are some products known to be produced by specific microalgae?

    <p>Chlorella zofingiensis is known for producing Astaxanthin, a red carotenoid, while Chlorella protothecoides produces Lutein, a yellow carotenoid.</p> Signup and view all the answers

    1. What is an example of food poisoning caused by Protozoa?

    <p>Ciguatera, caused by Gambierdiscus toxicus, is an example of food poisoning caused by Protozoa.</p> Signup and view all the answers

    1. What are the characteristics of viruses compared to bacteria cells?

    <p>Viruses are generally much smaller than bacteria and can only replicate inside the living cells of organisms.</p> Signup and view all the answers

    1. How do humans usually get infected with viruses that cause foodborne illnesses?

    <p>Humans usually get infected with viruses via ingestion, shedding in feces, contaminated water sources, and food contamination caused by food handlers or carriers.</p> Signup and view all the answers

    1. What is primary contamination of food and give an example?

    <p>Primary contamination occurs when food is naturally contaminated during primary production. An example is filter-feeding shellfish being contaminated at the water source.</p> Signup and view all the answers

    1. What is secondary contamination of food and who or what causes it?

    <p>Secondary contamination is caused by food handlers, carriers, or the contaminated food preparation area.</p> Signup and view all the answers

    1. Name three common viruses causing foodborne illness.

    <p>Three common viruses causing foodborne illness are Norovirus, Rotavirus, and Hepatitis A virus.</p> Signup and view all the answers

    What is the purpose of the Thermal Death Time (TDT) curve?

    <p>The TDT curve shows the relationship between temperature and time needed to kill microorganisms.</p> Signup and view all the answers

    What does the D-value represent in food preservation?

    <p>The D-value is the time required to kill 90% of microbial population and varies with temperature.</p> Signup and view all the answers

    How does refrigeration affect microbial growth?

    <p>Refrigeration (2-8˚C) slows microbial growth.</p> Signup and view all the answers

    What is the purpose of Modified Atmosphere Packaging (MAP) in food preservation?

    <p>MAP alters the gaseous environment to preserve food freshness.</p> Signup and view all the answers

    How does dehydration inhibit microbial growth?

    <p>Dehydration inhibits microbial growth by reducing water activity.</p> Signup and view all the answers

    In food preservation, what are the aims and principles of food preservation?

    <p>Aims of food preservation include preventing spoilage, extending shelf life, minimizing spoilage microorganisms, and ensuring food safety. Principles of food preservation include the elimination or inactivation of microorganisms, stopping enzyme action, and preventing oxidation through physical, chemical, and biological methods of food preservation.</p> Signup and view all the answers

    What are the symptoms and transmission methods of Norovirus?

    <p>Norovirus symptoms include vomiting, diarrhea, fever, and nausea. It is mainly transmitted through hand-to-mouth contact, direct contact, and consumption of contaminated shellfish and salad.</p> Signup and view all the answers

    What are the symptoms and transmission methods of Rotavirus?

    <p>Rotavirus causes vomiting, diarrhea, nausea, fever, and potentially death in severe cases. It is transmitted through fecal-oral and person-to-person transmission, food and waterborne.</p> Signup and view all the answers

    What are the symptoms and onset time of Hepatitis A virus infection?

    <p>Hepatitis A virus infection has an onset time of 12-50 days and symptoms including fatigue, diarrhea, liver damage, and extensive liver damage.</p> Signup and view all the answers

    What are the symptoms and causes of foodborne illnesses related to molds?

    <p>Molds primarily produce mycotoxins, causing foodborne illnesses like ergot poisoning from Claviceps purpurea, affecting neurons and leading to symptoms such as vision problems, confusion, unconsciousness, and gangrene in toes and fingers. Aflatoxin poisoning, caused by Aspergillus species, occurs in grains and nuts under damp and warm conditions, and its symptoms include liver degeneration, tumor, and stunted growth in children.</p> Signup and view all the answers

    1. What is pasteurization and how does it work in food processing?

    <p>Pasteurization is a thermal process used to inactivate enzymes and eliminate viable pathogenic microorganisms from heat-sensitive foods such as milk, fruit juice, wine, and egg. It involves heating the food to below 100˚C for a specific duration and then rapidly cooling it to slow down microbial growth, requiring refrigeration storage and providing a shelf life of 2-3 weeks.</p> Signup and view all the answers

    1. What are the two main methods of pasteurization and their respective temperature and duration?

    <p>The two main methods of pasteurization are low-temperature pasteurization at 63˚C for 30 minutes and high-temperature short time (HTST) pasteurization at 72˚C for 15 seconds.</p> Signup and view all the answers

    1. What is ultra-high temperature (UHT) pasteurization and how does it differ from regular pasteurization?

    <p>Ultra-high temperature (UHT) pasteurization of raw milk involves heating the milk to around 138 °C for 2-3 seconds, then rapidly cooling and packaging it in sterile, hermetically-sealed containers, providing a shelf-stable product for 6 months without requiring refrigeration until opened.</p> Signup and view all the answers

    1. What is sterilization in food processing and how is it achieved?

    <p>Sterilization is a process that completely kills or removes all life forms, including bacteria and other organisms, and is commonly achieved through heating methods such as wet heating at 121°C for 15-20 minutes.</p> Signup and view all the answers

    1. What is the significance of D value in measuring thermal-killing efficiency?

    <p>D value represents the time needed to reduce the number of a given microorganism by 90% at a specific temperature, and it decreases as the temperature increases, differing for different microbial species.</p> Signup and view all the answers

    Study Notes

    Microorganisms and Their Impact on Daily Life

    • Microorganisms like bacteria, viruses, fungi, and protozoa can cause foodborne illnesses and food spoilage.
    • Examples of foodborne diseases caused by microorganisms include cholera, avian influenza, and ciguatera food poisoning.
    • Microorganisms can be detected in food using specific methods.
    • Microorganisms are classified based on characteristics such as cell shape, size, and structure arrangement.
    • The classification of microorganisms involves scientific and common names.
    • The scientific name follows specific rules, such as italicizing or underlining the genus and species.
    • Microorganisms are classified into six kingdoms, including Protista, Fungi, Archaebacteria, and Eubacteria.
    • Protista can be single-celled or multi-celled and exhibit different modes of growth like photoautotrophic, heterotrophic, and mixotrophic.
    • Fungi include both single-celled (yeasts) and multi-celled (molds) organisms that grow without light.
    • Archaebacteria are single-celled organisms that often live in extreme conditions, such as thermophiles.
    • Eubacteria, also single-celled, can live in various environments and can exhibit photoautotrophic, heterotrophic, or mixotrophic growth.
    • Bacteria, which are prokaryotes and lack a membrane-bound nucleus, can impact daily life by causing food spoilage and diseases, serving as a source of drugs, and being a source of vitamins and nutrients.

    Microbes in Biology

    • Bacteria are identified based on cell structure and can be Gram positive (blue/purple) or Gram negative (red).
    • Mechanism of bacteria gram staining involves fixed cells on a slide and staining with crystal violet-iodine complex.
    • Viruses are obligate intracellular parasites and can be host-specific, with a size of 10nm compared to bacteria cell size of 1µm.
    • Viruses replicate by inserting genetic materials into host cells, leading to lysis of the host cell wall.
    • Some viruses, like Avian Influenza (Bird Flu) caused by H5N1 virus, can cause food poisoning.
    • Microalgae are a large group of microbes found in various environments, including soil, fresh water, and marine environments.
    • Microalgal cell structure includes a cell wall, chloroplast for photosynthesis, and mitochondrion for respiration.
    • Green microalgae, such as Chlamydomonas and Chlorella, can be unicellular, motile or non-motile, and reproduce asexually or sexually.
    • Chlorella zofingiensis is known for producing Astaxanthin, a red carotenoid used as a natural food colorant.
    • Chlorella protothecoides produces Lutein, a yellow carotenoid used as a food colorant in egg yolk.
    • Protozoa are single-celled, eukaryotic organisms that can be photoautotrophic, heterotrophic, or mixotrophic.
    • Food poisoning caused by Protozoa includes Ciguatera, caused by Gambierdiscus toxicus.

    Pasteurization and Sterilization in Food Processing

    • Pasteurization is a thermal process used to inactivate enzymes and eliminate viable pathogenic microorganisms from heat-sensitive foods such as milk, fruit juice, wine, and egg.
    • It involves heating the food to below 100˚C for a specific duration and then rapidly cooling it to slow down microbial growth, requiring refrigeration storage and providing a shelf life of 2-3 weeks.
    • Pasteurization involves two main methods: low-temperature pasteurization at 63˚C for 30 minutes and high-temperature short time (HTST) pasteurization at 72˚C for 15 seconds, with the latter being more effective in retaining nutritional and sensory quality.
    • HTST pasteurization of raw milk involves heating the milk briefly to 72 °C for about 15 seconds to kill disease-causing microbes, followed by rapid cooling and refrigeration storage.
    • Ultra-high temperature (UHT) pasteurization of raw milk involves heating the milk to around 138 °C for 2-3 seconds, then rapidly cooling and packaging it in sterile, hermetically-sealed containers, providing a shelf-stable product for 6 months without requiring refrigeration until opened.
    • Sterilization is a process that completely kills or removes all life forms, including bacteria and other organisms, and is commonly achieved through heating methods such as wet heating at 121°C for 15-20 minutes.
    • Commercial sterilization combines heat and vacuum seal to destroy all spoilage and pathogenic microorganisms, including endospores of Clostridium botulinum, used in producing canned food through retort processing.
    • Canning involves commercial sterilization of low acid foods at 121°C for a duration sufficient to inactivate Clostridium botulinum spores by 12 log and high acid foods at around 100°C to destroy both vegetative cells and spores of spoilage microorganisms.
    • One log reduction indicates a 90% reduction in the microbial population, and 12 log reduction signifies a complete eradication of the microorganisms.
    • Bacterial populations killed by heat or chemicals tend to die at constant rates, with the microbial death rate curve showing this constant death as a straight line.
    • Three important values used to measure thermal-killing efficiency are D value (decimal reduction time), Z value (increase in temperature required to reduce D value by ten-fold), and F value.
    • D value represents the time needed to reduce the number of a given microorganism by 90% at a specific temperature, and it decreases as the temperature increases, differing for different microbial species.

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    Description

    Test your knowledge of microbes in biology with this quiz. Explore topics such as bacteria cell structure, gram staining, virus replication, microalgae characteristics, and the classification of microorganisms. Learn about the impact of microorganisms on daily life, including foodborne illnesses and food spoilage.

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