Lecture 22: The Microbe-Human Ecosystem

Question 1

Microbiome

Answer 1

• All the genes found in one’s microbiota

Question 2

Microbiota

Answer 2

• all the microorganisms that live in and on an organism

Question 3

Holobionts

Answer 3

• Hosts and microbes that live and evolve together
• each microbial nice is related to a variety of factors such as body location, age, sex, diet and environment

Question 4

Microbiome- development

Answer 4

• Microbiota community is not static
• Begins developing at birth and changes as we age
• A stable community of microbes adopted by age 3
• It is important to develop a diverse microbiome

Question 5

Microbiome- development; Early Life

Answer 5

• Newborn colonization important.
• Vaginal birth provides
  exposure to microbes from the mother’s birth canal, whereas cesarean delivery provide microbe exposure from initial caretakers

Question 6

Bifidobacteria

Answer 6

• Transport polymeric sugars found in human breast milk directly across their plasma membrane
• Fermentation of these sugars provides the infant with calories and lowers the gut pH, limiting growth of pathogens

Question 7

Microbiome- development; adulthood

Answer 7

• Relatively stable over time
• Only change due to physical or lifestyle changes
• Variable from person to person and at different sites within a person
• Bacteria common to human skin, the intestinal tract, and the other mucosal surfaces include six major phyla:
  1. Actinobacteriota
  2. Bacteroidota
  3. Firmicutes
  4. Fusobacteriota
  5. Proteobacteria
  6. Verrucomicrobiota

Question 8

Skin Microbiota

Answer 8

• Environment:
  Slightly acidic pH
  High concentration of NaCl
  Some areas lack moisture
  Some bathed in oily
  lubricant sebum and
  antimicrobial peptides
• Some microbes are transient and typically unable to multiply on the skin
• 3 environmental niches:
  1. dry
  2. Moist
  3. sebaceous

Question 9

Respiratory tract

Answer 9

• Upper respiratory tract: nostrils, sinuses, pharynx, and oropharynx
• colonized by a diverse group of microbes
• Lower respiratory tract: larynx below the vocal cords, trachea, bronchi, and lungs

Question 10

Staphylococcus epidermidis

Answer 10

• nonpathogenic
• Secreting products of fermentation called short chain fatty acids
• Bacterial interference: inhibits growth of pathogens

Question 11

Oral cavity- gastrointestinal tract

Answer 11

• Anaerobes: dominant due to the anoxic nature of the space between the teeth and gums
• As teeth grow,Streptococcus parasanguinis attach to enamel surfaces; S. salivarius attaches to the cheeks and gum epithelia and colonizes
  the saliva
• Produce a glycocalyx and various other adherence factors that enable them to attach to oral surfaces: Contribute to dental plaque

Question 12

Stomach: gastrointestinal tract

Answer 12

• acidophiles
• microorganisms may survive: if pass thru the stomach quickly and if ingested with food particles and are resistant to gastric pH

Question 13

Small intestine- gastrointestinal tract

Answer 13

3 areas:
1. Duodenum
2. Jejunum
3. ileum

Question 14

Duodenum

Answer 14

• contains few organisms due to stomach acid, bile, and
  pancreatic secretions; Gram-positive bacteria comprise most of the microbiota

Question 15

Jejunum

Answer 15

• Enterococcus faecalis, lactobacilli, diphtheroids, and the yeast Candida albicans found

Question 16

ileum

Answer 16

• flora similar to that in colon;
  pH becomes more alkaline; anaerobic Gram-negative bacteria and members of the family Enterobacteriaceae become established

Question 17

Large intestine- gastronintestinal tract

Answer 17

• one of the most densely packed microbial ecosystems on earth
• gut microbiome has metabolic, immunological, and endocrine roles

Question 18

Genitourinary tract

Answer 18

• kidneys, ureter&urinary bladder: free of microbes
• distal urethra: few microbes found
• Vaginal microbes: complex microbiota that changes due to menstrual cycle and acid tolerant lactobacilli predodminate

Question 19

Functional core microbiome

Answer 19

• microbes provide the host with a suite of activities required for health and homeostasis
• Provision of vitamin K and B by E. coli

Question 20

Host metabolism

Answer 20

• gut microbiota converts food into calories
• fat ppl: higher concentrations of gut bacteria belonging to the phylum Firmicutes compared to bacteria belonging to the phylum Bacteroidota
• Has refocused attention from the individual species in the gut microbiome to the metabolome (products microorganisms secrete)

Question 21

Effect of the Microbiota- Immunity

Answer 21

• Antibiotics disrupt the gut microbial community
• Following antibiotics treatment, people are at higher risk of GI tract, yeast infections
• Colonization resistance: competitive exclusion by resident microbes

Question 22

Microbiota regulate host immune system- Immunity

Answer 22

• Gut microbes communicate with host via Toll-like receptors (TLRs)
• The more diverse the microbiome, the better the
  immune cells will become at
  distinguishing between harmful pathogens and harmless bacteria

Question 23

Microbiota regulare inflammation- immunity

Answer 23

• Mucosal tolerance: how microbes reside in our gut
  without an overwhelming inflammatory response
• Balance between pro-inflammatory cells, which
  produce the anti inflammatory cytokine IL-10

Question 24

Central Nervous System

Answer 24

3 ways microbiome can influence the CNS:
1. Microbiome impacts the immune system
2. Direct pathway from gut to brain through nerves in GI tract which transmit signals to the brain via the vagus nerve
3. Soluble microbial products cross the blood brain barrier

Question 25

Dysbiosis

Answer 25

• pathological changes in the gut microbiome that lead to disease
• leads to inflammation

Question 26

Metabolic syndrome

Answer 26

• characterized by at least 3 of the following:
  1. Large waist circumference.
  2. High blood triglyceride level.
  3. High blood pressure.
  4. Elevated low-density lipoprotein.
  5. High fasting blood glucose levels
• Linked to the microbiome as explained by metabolic
  endotoxemia

Question 27

Probiotics

Answer 27

• “Live microorganisms, which, when administered in adequate amounts, confer a health benefit to the host”

Question 28

Prebiotics

Answer 28

compounds added to enhance the colonization and positive health benefits of probiotic microbes

Question 29

Metabolic Endotoxemia

Answer 29

• known as leaky gut