MICR501 Q3 Tutorial Questions

Which is the most accurate definition of a microorganism?

An organism that you cannot see using your naked eye

Which of the following does NOT describe darkfield microscopy?

Shows clear magnification

When would you use fluorescence microscopy?

To visualise specific proteins or nucleic acids tagged with fluorescent dyes

Who is commonly referred to as the ‘Father of Microbiology’ because he was one of the first to see microbes and called them ‘animalcules’?

Antoine van Leeunwenhoek

Who created the compound microscope?

Robert Hooke

Describe how electron microscopy works

A beam of electrons and their wave-like characteristics is used to magnify an object’s image. The wavelength of an electron is much smaller than that of visibly light, providing a much higher resolution.

Describe what we use electron microscopy for

View smaller microbes like viruses as well as large biological molecules

Koch’s postulates 1-3

1. Must be found in abundance in diseased individuals only

2. Microorganism must be isolated and grown in pure culture

3. Cultured microorganism should cause disease when introduced into a healthy organism

Koch’s postulates 4

Microorganism must be re-isolated from inoculated/diseased experimental host and identified as being identical to the original specific causative agent

Endosymbiosis theory

Describes that two of the main eukaryotic organelles arose from two major evolutionary events

Evidence of endosymbiosis theory

Mitochondria and chloroplasts are similar size to bacteria, divide by binary fission, have their own circular DNA, have their own ribosomes, have inner membranes

Endosymbiosis: eukaryotes

Ancestral prokaryotic cell acquired a heterotrophic prokaryotic which becomes the mitochondrion that generates cellular energy in modern eukaryotes

Endosymbiosis: photosynthetic eukaryotes

Host cell with mitochondria additionally acquired a photosynthetic prokaryote which becomes the chloroplast in modern photosynthetic eukaryotes

Which of the following best describes chemolithoheterotrophs?

Organisms that use inorganic compounds as an energy source and organic compounds as a carbon source

Which of the following statements is false?

Environmental pressures can result in a population decline of those individuals that thrive under the pressures

Which of the following statements is false?

K-strategists have rapid growth rates while r-strategists demonstrate optimal use of resources

 What is the significance of natural selection for microbes in their environment?

Microbes must adapt to their environment or face extinction.

 What does taxonomy involve in the context of microbial classification?

Categorising organisms based on their similarities

Describe microbial competition and give three examples of how microbes compete with each other

Microbes which inhabit the same environment compete for nutrients, space and other resources

Inhibiting the growth of other microbes — e.g. producing antimicrobial compounds

Better/faster utilisation of the resources available

Utilising resources not available to the other microbes

Explain how natural selection and adaptation contribute to the diversity we observe in microbial communities

• Natural selection is the process by which advantageous traits become more common in a population over time

• In microbial communities, this happens rapidly due to short generation times and large population sizes

• Microbes are exposed to a large range of environmental pressures and through genetic mutation or recombination microbes can adapt to survive these conditions

• Ultimately, all these adaptations lead to more diverse traits across all microbes

Obligate aerobes

Need oxygen because they cannot ferment or respire anaerobically

Obligate anaerobes

Poisoned by oxygen

Facultative anaerobes

Can grow without oxygen because they can metabolise energy aerobically or anaerobically

Microaerophiles

Need oxygen because they cannot ferment or respire anaerobically but are poisoned by high concentrations of oxygen

Aerotolerant organisms

Do not require oxygen as they metabolise energy anaerobically, but are not poisoned by oxygen

Levels of ecological organisation

Kingdom, Phylum, Class, Order, Family, Genus, Species

Define mutation

A heritable change in the base sequence of a nucleic acid genome of an organism

Define horizontal gene transfer

Two unrelated individuals passing or exchanging genes through sexual or asexual reproduction

Define origin of replication

Specific DNA sequence where the replication of a DNA molecule begins

Define nucleoid

Region within prokaryotic cell containing the cell’s genetic material

Which of the following statements about prokaryotic cell structures is false?

Many bacterial cells secrete some extracellular material in the form
of a capsule or a slime layer. A capsule is loosely associated with the
cell and can be easily washed off, whereas a slime layer is attached
tightly and has definite boundaries.

Which of the following structures are typically present in all bacterial and archaeal cells?

Cell wall, cytoplasmic membrane, ribosomes, nucleoid

Which of the following statements most accurately describes the process of conjugation?

When one bacterium passes genetic material to another bacterium through direct contact

Which substance is found in the cell walls of archaea but not in bacteria?

Pseudopeptidoglycan

Which of the following describes a frameshift mutation?

A mutation caused by the insertion or deletion of nucleotides that alters the reading frame of the genetic code

Lake zones

Littoral zone, limnetic zone, profundal zone, benthic zone

Conditions in littoral zone

Near shore, sunlight penetrates to sediment floor, aquatic plants able to grow, aerobic

Bacteria found in littoral zone

Photosynthetic algae/bacteria

Conditions in limnetic zone

Open water, some sunlight, aerobic high up and microaerobic further down

Bacteria found in limnetic zone

Photosynthetic microbes, if sufficient oxygen will contain pseudomonas and species of cytophaga, caulobacter, and hyphomicrobium

Conditions in profundal zone

Low level of light, microaerobic or anaerobic

Bacteria found in profundal zone

Purple and green sulphur bacteria

Conditions in benthic zone

Bottom sediment, sunlight does not penetrate, anaerobic, surface layer abundant with organisms

Bacteria found in benthic zone

Auto and heterotrophic bacteria, desulfovibrio, clostridium, microbes vital to nutrient flow between sediment layers and water column

Factors affecting bacteria in aquatic environments

Organic matter, nitrogen, phosphorus, pH, DO, temperature

Difference between carbon capture and storage (CCS) and carbon capture and utilisation (CCU)

After removal of CO2, CCS permanently stores it elsewhere while CCU utilises it to make products such as biofuel

Difference between modern and traditional cheese making

Large scale production inoculates cheese with preselected cultures consisting of a few types of microbes, give consistent results and are easy to scale up

Traditional cheeses are inoculated using whey/products from previous batches and can contain dozens of types of microbes, are harder to control and reproduce, more complex

Which of the following is NOT a domain in the three-domain system?

Animalia

Which is the most accurate definition of a microorganism?

An organism that you cannot see using your naked eye

Which of the following does NOT describe darkfield microscopy?

Shows clear magnification

What was the role of microorganisms in the evolution of life?

They were involved in the development of multicellular organisms and the oxygenation of the atmosphere

Which of the following best describes a Chemolithoheterotroph?

Organism that uses inorganic compounds as an energy source and organic compounds as a carbon source

Which of the following statements on microbial competition is FALSE?

Microbes can gain a competitive advantage over others by having slower utilisation rates of the available resources

Which of the following statements is FALSE?

K-strategists have rapid growth rates while r-strategists demonstrate optimal use of resources

Which of these describes microorganisms that are capable of utilising oxygen when present but are able to grow without the presence of oxygen?

Facultative anaerobic microorganisms

Which of the following statements most accurately describes the process of conjugation?

When one bacterium passes the genetic material to another bacterium through direct contact (can be plasmid or chromosome)

Which of the following is NOT a type of point mutation?

Frameshift mutation

Which of the following statements on the genetic material of prokaryotic cells is FALSE?

Archaea only have one origin of replication site on their chromosome

Which of the following statements on microbes in freshwater aquatic environments is FALSE?

Natural freshwater ecosystems are oligotrophic meaning they have high nutrient concentrations

Which of the following is NOT a characteristic of traditional cheese making?

Easy to scale up

Which of the following would NOT be considered biotechnology?

Using chemical cleaners to kill microbial organisms

Which of the following statements on carbon capture is FALSE?

'Direct air capture' is a form of carbon capture where the carbon is sourced directly from things like electricity generation plants and industrial processing

Which of the following characteristics describes Bacillus cereus?

Gram-positive rod-shaped bacterium, aerobic or facultatively anaerobic, spore forming

What is the difference between a bactericidal and bacteriostatic antimicrobial?

Bactericidal is an antimicrobial that not only inhibits growth but is lethal to bacteria, while Bacteriostatic only inhibits growth but does not kill the organism

Which of the following statements on the human microbiota is FALSE?

It is comprised of bacteria, archaea, viruses and eukaryotes

Which of the following antibiotics works by inhibiting protein synthesis?

Tetracycline

Provide a definition for ‘systematics’

Study of evolutionary history/relationships among organisms.

Describe microbial competition

Microbes inhibiting the same area competing with each other for resources to survive such as space and nutrients

Three examples of how microbes compete

Rapidly utilising resources before other microbes can

Producing antibiotics to inhibit the growth of other microbes

Utilising resources unavailable to other microbes

Provide a definition for ‘plasmid’

Small, circular-shaped extrachromosomal DNA molecule located in cytoplasm of some prokaryotic cells that can replicate independently of chromosomal DNA

Describe the prokaryotic cell cycle

1. DNA replicates starting from origin of replication

2. Cell elongates

3. Septum forms down middle of cell

4. Cell splits into two

Provide a definition for ‘extremophile’

Organism able to thrive in extreme environments (in which most other organisms, esp humans wouldn’t be able to)

Environmental condition Halobacteria have adapted to survive in

High salt concentration environments

Adaptations of Halobacteria to cope with environment

Unique lipids in membrane to help maintain structure, high PCl concentration to counteract osmotic pressure, proteins adapted to prevent denaturation

Describe the role of a healthy gut microbiota

Break down foods we cannot digest ourselves

Produce n-butyrate when digesting carbohydrates

Synthesis of vitamins, AAs, and lipids

Make small molecules that enter blood stream and travel through body and impact metabolism

Help train immune system

Release compounds that can aid in reducing inflammation

Describe eutrophication

Excessive plant/algal growth due to increased availability of 1 or more limiting growth factors needed for photosynthesis

Consequences of eutrophication

Dense algal blooms block light from rest of lake, increased photosynthesis reduces available CO2, lake eventually no longer supports algal bloom causing a die-off, microbial decomposition of dead algae severely depletes DO, creates hypoxic/anoxic dead zone lacking sufficient oxygen to support most organisms