This quiz tests basic microbiological concepts you’ll need for pre-clinical medicine, as well as touching on aspects of gut flora. Good luck!
Reviewed by: Jonathan Loomes-Vrdoljak, 28 February 2020
Introduction to Microbes & Flora
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Which of the following microorganisms are prokaryotes?
Question 1 Explanation:
Bacteria are prokaryotic organisms. Fungi & Protozoa are eukaryotic organisms. Viruses & Prions are neither.
Which of these diseases are caused by a viral infection?
Question 2 Explanation:
Smallpox is caused by the Variola major or minor virus. Tuberculosis, tetanus and diptheria are all caused by bacterial infections, and malaria is caused by a protozoan infection.
Which of the following diseases is caused by an infectious agent that has no genetic material?
Question 3 Explanation:
Creutzfeld-Jakob disease is caused by prions. These are infectious, misfolded proteins that contain no DNA or RNA, have no independent metabolism and contain no organelles. Chickenpox is caused by Varicella-zoster virus (VZV), which has a double-stranded DNA. Japanese encephalitis is caused by the Japanese encephalitis virus (JEV), which has a single-stranded RNA genome. Rabies is caused by Lyssavirus (this includes the rabies virus), which has a single-stranded RNA genome. Tetanus is caused by toxins from the bacteria Clostridium tetani.
Leishmania donovani is an example of what type of microbial organism?
Question 4 Explanation:
Leishmania donovani is an example of a protozoan infection, and causes the disease leishmaniasis.
Which of the following statements best describes the structural difference between Gram negative and Gram positive bacteria?
Gram positive bacteria have a thick peptidoglycan cell wall with no outer lipid membrane, whereas Gram negative bacteria have a thin peptidoglycan cell wall and an outer lipid membrane
Gram positive bacteria have a thick peptidoglycan cell wall, whereas Gram negative have a lipid membrane
Gram negative bacteria have a thick peptidoglycan cell wall with no outer lipid membrane, whereas Gram positive bacteria have a thin peptidoglycan cell wall and an outer lipid membrane
Gram negative bacteria have a thick peptidoglycan cell wall, whereas Gram positive have a lipid membrane
Gram positive bacteria have a peptidoglycan cell wall and lipid membrane, whereas Gram negative only have a lipid membrane
Question 5 Explanation:
The difference in structure between Gram negative and Gram positive cells can be demonstrated using a Gram stain technique! Gram positive bacteria have a thick outer peptidoglycan layer and no outer lipid membrane. The outer peptidoglycan layer is thick enough to retain crystal violet dye and causes them to appear purple. Gram negative bacteria have a thin peptidoglycan layer, surrounded by an outer lipid membrane. The thin layer of peptidoglycan is not able to retain the crystal violet dye, but is able to pick up the safranin counterstain, which causes them to appear pink-red.
Which of these cell components are found in both bacteria and human cells?
Question 6 Explanation:
Ribosomes are found in both bacteria and human cells - they are involved in protein synthesis. Cell capsules, cell walls and nucleoids are only found in bacteria, whereas centrioles are only found in humans cells.
Which of the following statements best describes a commensal relationship between species?
A relationship between two species, where they work together to positively impact each other's growth
A relationship between two species, where the presence of one causes harm to the other
A relationship between two species, where one derives some benefit and the other is unaffected
The relationship between the two species has no effect
Where one species has taken advantage of the other being weakened, to invade and multiply
Question 7 Explanation:
The key to a commensal relationship is that only one of the organisms is receiving benefit, and the other is completely unaffected. If both organisms benefit, the relationship is mutualistic. If one organism benefits and the other is harmed, the relationship is parasitic.
How do the microflora help to prevent infection in the gastrointestinal tract?
They make use of the available nutrients, ensuring they are not available for pathogens
They secrete compounds that kill or inhibit pathogens
They fully colonise the space, meaning the pathogens cannot adhere to the intestinal wall
All of the above
None of the above
Question 8 Explanation:
The gut flora have a multitude of functions, that all aid in boosting our immunity against ingested pathogens!
Which of the following statements best describes infection?
The invasion and multiplication microbes in an area of the body where they’re not normally present, causing symptomatic disease
The presence of microbes in the human body, causing sickness and disease
When normal gut flora start to produce toxic metabolites, which affect the host negatively causing symptoms of disease
A systemic response to microbes, causing sickness and fever.
The invasion and multiplication of microbes in an area of the body where they’re not normally present, which usually leads to disease. This may or may not be symptomatic.
Question 9 Explanation:
An infection is not always a asymptomatic disease. It can be subclinical/asymptomatic!
An obligate pathogen takes advantage of an opportunity that is not normally available, such as infecting a host with a weakened immune system, an altered microbiota, or breached integumentary barriers. True or false?
Question 10 Explanation:
This statement describes an opportunistic pathogen. An obligate pathogen is one that must cause disease in order to be transmitted from one host to another. They must infect a host in order to survive.
Which of the following is not a step in Koch’s postulates?
The micro-organism must be found in abundance in all organisms suffering from the disease and not in healthy organisms
The micro-organism must be isolated from a diseased organism and grown
A photomicrograph of the cultured micro-organism should be taken and recorded appropriately
The cultured micro-organism should prove to cause disease in healthy organisms
The micro-organism should be re-isolated from the diseased experimental hosts and be identified as identical to the original specific causative agent
Question 11 Explanation:
Koch's postulates are used to establish a causative relationship between a microbe and a given disease. A photomicrograph is not one of the requirements for this process.
Which of the following is not a biochemical barrier to infection?
Sebaceous secretions in the skin
Lysozyme in the tears
Spermine in the sperm
Question 12 Explanation:
The respiratory cilia are a physical barrier to infection, rather than a biochemical barrier.
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