Microbial Ecology Flashcards

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1
Q

How are microbes ubiquitous in nature?

A
  1. Interact w/ hosts ( Humans, animals, plants etc )
  2. Diverse ( viruses, fungi, bacteria etc )
  3. Tolerate different temperatures, utilize different nutrients & produce different metabolites
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2
Q

Define Host-Microbe relationship :

A
  • How host microorganisms sustain themselves within host organisms
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3
Q

Define Microbial ecology :

A

Study of interactions between microbes & their environment

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4
Q

What is symbiosis? Give an example.

A
  • Interaction between host & organism

- Example: Human/animal skin & mucous membranes generate an environment for microorganisms

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5
Q

What are the three forms of symbiotic relationships ?

A
  1. Mutualism
  2. Commensalism
  3. Parasitism
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6
Q

What is Mutualism? Give an example.

A
  • Both the microorganism & the body work together w/out causing harm to each other.
  • E.coli in the human intestine
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7
Q

What is Commensalism? Give an example.

A
  • Either the body or the microorganism benefits, while the other is not affected.
  • Microrganisms that inhabit the eyes.
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8
Q

What is Parasitism? What do they use in the human body?

A
  • One organism benefits at the expense of the other.

- Gastrointestinal tract of humans.

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9
Q

What are the two types of Microorganisms with relation to disease?

A
  1. Parasitic pathogens (microbes that cause disease)

2. Non-parasitic non-pathogens (microbes that do not cause disease)

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10
Q

What are biofilms?

A
  • community of microbial cells attached irreversibly to the substrate @ the interface or to each other
  • embedded in an exopolysaccharidic matrix
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11
Q

What role do biofilms play?

A
  • Implant of medical devices, such as intravascular catheters
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12
Q
  • What are the 5 steps of biofilm formation called?
A
  1. Reversible attachment
  2. Irreversible attachment
  3. Colonization
  4. Maturation
  5. Dispersion
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13
Q

Explain the 5 steps of biofilm formation :

A
  1. Individual cells population the surface ( initial attachment )
  2. Extrapolymeric substances (EPS) are produced & attachment becomes irreversible
  3. Saturation
  4. Biofilm architecture develops & matures
  5. Single cells are released from the biofilm
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14
Q

What is the clinical significance of biofilms?

A
  • Infection of medical implants & devices
  • Cause recurrent & difficult to treat infections
  • Device-associated infections usually resistant to antibiotics, immune to defense mechanisms
  • Biofilm bacteria release antigens & stimulate production of antibodies, yet bacteria residing in biofilms are resistant to these defense mechanisms
  • This above immune response may even cause damage to the surrounding tissue
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15
Q

What are the bacteria associated with biofilms?

A
  • Gram-Positive bacteria :
    • Enterococcus faecalis
    • Staphylococcus aureus
    • Staphylococcus epidermis
    • Streptococcus viridans
    • Bacillus cereus
    • Candida albicans
  • Gram-negative bacteria :
    • Escherichia coli
    • Klebsiella pneumoniae
    • Proteus mirabillis
    • Pseudomonas aeruginosa
    • Salmonella enterica
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16
Q

Describe the infectious disease cycle:

A
  1. The pathogen : organism causing infection
  2. The host : Infected person or animal
  3. The entry : Method pathogen used to enter host
  4. Transmission : How pathogen goes from host to host
  5. Environment : Where transmission of pathogen takes place
  6. Exit : Method pathogen uses to leave body of host
17
Q

What are the two types of pathogens? Define them & give examples.

A
  • Primary pathogens : Always cause disease
    • Vibrio cholerae, M. Tuberculosis, Treponema pallidum
  • Opportunistic pathogens : Resident or transient flora that can cause disease under certain conditions
    • Staphyloccus aureus, Escherichia coli
18
Q

What determines potential pathogenicity?

A
  • Number of pathogens
  • virulence
  • nature & magnitude of host defenses
19
Q

Define Host defenses & give examples :

A
  • A microorganism will not be able to invade unless it overcomes an animal’s/individual’s host defenses.
  • Skin & mucosal secretions
  • Non-specific local responses (pH)
  • Non-specific inflammatory responses
  • Specific immune responses ( lymphocytes )