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+ MICB 202 Final > Bacteria Chapter 3-4: Microbiota of Humans > Flashcards

Bacteria Chapter 3-4: Microbiota of Humans Flashcards

1
Q

Where in the human body are there normally no bacteria (sterile)?

A
  • blood
  • brain
  • muscle
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2
Q

How do bacteria benefit from the host?

A
  • nutrient supply
  • stable environment
  • mode of transport
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3
Q

How do hosts benefit from bacteria?

A
  • microbial antagonism
  • nutritional synergisms (bacteria in GI tract)
  • stimulation of immune system
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4
Q

What is microbial antagonism?

A

microbiota inhibits colonization by pathogens

  • occupy adherence sites
  • use nutrients
  • produce inhibitory byproducts
  • affect pH
  • affect oxygen availability
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5
Q

What are bacteria in GI tract involved in?

A
  • synthesis and excretion of excess vitamins, which can be absorbed as nutrients by host (vitamin K, vitamin B12)
  • steroid metabolism, which is then reabsorbed by host
  • organic acid production
  • glycosidase reactions
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6
Q

What are natural antibodies?

A

antibodies produced against components of microbiota

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7
Q

How do bacteria stimulate host immune system?

A
  • microbiota can induce antibody response in host

- low levels of natural antibodies can cross react with certain related pathogens, preventing infection or invasion

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8
Q

Bacteria of the microbiota resist innate immune defences and do not elicit strong adaptive immune responses that would lead to their elimination.

A
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9
Q

How can microbiota possible detoxify the microbiota’s LPS?

A

induction of phosphatase in intestinal epithelial cells by bacteria of the microbiota

could render them less sensitive to innate immune system

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10
Q

What are harmful/unwanted aspects of the host-microbiota relationship?

A
  • microbiota could become pathogenic if introduced into other locations in the body
  • production of intestinal gas in large intestine
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11
Q

When are humans free of microorganisms?

A

prior to birth (fetal)

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12
Q

How is microbiota obtained from the environment immediately after birth?

A
  • passage through birth canal
  • exposure to other humans (and pets)
  • ingestion of food and fluids
  • inhalation of air-borne microorganism
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13
Q

What happens to the composition of the microbiota once it is established?

A

remains relatively constant, but can change with changing circumstances (ie. diet)

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14
Q

What are factors that can affect composition of microbiota?

A
  • diet
  • infection
  • oral antibiotic therapy
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15
Q

What are the 3 explanations for why bacteria of the microbiota are located at a particular anatomical site?

A

tissue preference for colonization

  • host provides essential growth factor
  • some sites are inhospitable for colonization

host receptors that interact with specific bacterial ligands at colonization sites are expressed in only certain areas of the host body

biofilm

  • some members of microbiota can construct biofilms on tissue surface
  • other members of microbiota establish themselves as part of biofilm built by another species
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16
Q

What are the locations of microbiota that live on and in the human body?

A
  • upper respiratory system
  • mouth
  • skin
  • small intestine
  • colon
  • appendix
  • urethra
  • vagina
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17
Q

Skin

What are most skin microorganisms associated (directly or indirectly) with? Why?

A

sweat glands – armpit, genitals, between toes

  • warm
  • high moisture

supports activity and growth of high density of bacteria

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18
Q

Skin

Why is the upper region of hair follicles (just below epidermis) good for microorganisms?

A

secretions of sebaceous gland of hair follicle contain microbial nutrients – urea, amino acids, salts, lactic acid and lipids

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19
Q

Skin

What prevents microorganisms from multiplying?

A

majority of skin microorganisms are transient (removed/transferred easily)

20
Q

Skin

What does not support the growth of most microorganisms?

A
  • low moisture
  • low pH (acidic)
  • competition with permanent residents of the microbiota
21
Q

Skin

What are some bacteria that can be found as part of the microbiota of skin?

A
  • Staphylococcus epidermidis (non-pathogenic, commensal)
  • Micrococcus (non-pathogenic, commensal)
  • Propionibacterium acnes (potentially pathogenic on hands and face/nostrils)
22
Q

Oral Cavity

Does saliva support microorganism growth?

A

no

  • few nutrients
  • antibacterial substances (lysozyme, lactoperoxidase)
23
Q

Oral Cavity

What does lysozyme do?

A

weakens bacterial cell walls by cleaving glycosidic linkages in peptidoglycan

24
Q

Oral Cavity

What does lactoperoxidase do?

A

kills bacteria in a reaction that generates singlet oxygen

25
Q

Oral Cavity

What supports microorganism growth?

A
  • food particles

- epithelial debris

26
Q

Oral Cavity

Compare the bacterial populations of microbiota before and after eruption of teeth.

A

before:
- aerotolerant anaerobes
- few aerobes

after:

  • anaerobes on tooth surface
  • anaerobes in gingival crevices
27
Q

Oral Cavity

What is plaque?

A

biofilm on tooth surface

  • provides attachment substances and colonization site for Streptococcus
28
Q

Oral Cavity

What is Streptococcus mutans?

A

bacteria association with dental cavities

29
Q

GI Tract

Are intestinal microbiota anaerobes or aerobes?

A

majority are anaerobes

30
Q

GI Tract

What are some anaerobic microorganisms found in the GI tract

A
  • E. coli (facultative anaerobe)
  • Bacteroides (strict anaerobe)
  • Lactobacillus (aerotolerant anaerobe)
31
Q

GI Tract – stomach

What prevents microorganism growth?

A

low pH

32
Q

GI Tract - stomach

What is Helicobacter pylori?

A

bacteria that can colonize stomach wall

causes gastric ulcers and gastric cancer

33
Q

GI Tract – large intestine

What is the large intestine (what type of bacterial growth does it support)?

A

anaerobic bacterial fermentation chamber

  • any oxygen that may be present is quickly consumed by facultative anaerobes
34
Q

Respiratory Tract

What are the nostrils heavily colonized by?

A
  • predominantly Staphylococcus epidermidis

- sometimes Staphylococcus aureus (potential pathogen)

35
Q

Respiratory Tract

What colonizes the sinuses?

A

nothing – sterile

36
Q

Respiratory Tract

Where in the URT do microorganisms colonize?

A

secretions of mucous membranes

37
Q

Respiratory Tract

What colonizes the LRT?

A

nothing – virtually free of microorganisms

38
Q

Respiratory Tract

How is the LRT free of bacteria?

A

ciliated epithelium sweeps bacteria upward into URT, then removed by coughing/sneezing/swallowing

39
Q

Respiratory Tract

What is Bordetella pertussis?

A

bacteria able to colonize tracheal epithelium – produces pertussis disease (whooping cough)

40
Q

Urogenital Tract

Why are all other parts normally sterile?

A

urine is normally sterile, and urinary tract is flushed with urine often

41
Q

Urogenital Tract

Which parts have microorganisms?

A
  • vagina

- urethra

42
Q

Urogenital Tract – vagina

What bacteria predominates in vagina, and how?

A

Lactobacillus

lower pH to 4-5 (optimal for them, but inhibits others)

43
Q

Urogenital Tract – vagina

What causes Candida (yeast infection)?

A

loss of protective effect of Lactobacillus (lowering the pH, which inhibits growth of other bacteria) by antibiotic therapy

44
Q

Urogenital Tract – urethra

What microorganisms are present?

A

may contain predominantly skin microorganisms

45
Q

Is the microbiota essential for life?

A

no, but is essential for living well

+ MICB 202 Final (20 decks)

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