Exam 1: Microbiome

Question 1

Microbiota

Answer 1

Collection of microbial organisms that live on or in a host.

(Bacteria, archaea, protists, fungi, and viruses)

Question 2

Microbiome

Answer 2

Entirety of the genomic content of the microbiota.

Question 3

Holobiont

Answer 3

A host + their microbiota

Question 4

Hologenome

Answer 4

Combined genetic content of host genome, organelle genomes, and microbiome.

Human genes ⇒ 23,000 genes

Microbiome ⇒ > 1 million genes

Question 5

Factors Affecting

Microbioata

Answer 5

• Genetics
• Gender
• Age
• Immune system
• Antropometric parameters
• Health/disease conditions
• Geography
• Socioeconomic factors
• Medical treatments
• Diet

Question 6

Gut flora accounts for up to ___ of the circulating metabolites in the body.

Answer 6

1/3

Question 7

Metagenomics

Answer 7

The study of the genetic material isolated from environmental samples.

Usually use 16S rRNA to ID groups of microbes.

Question 8

Transcriptome

Answer 8

All the RNA molecules expressed in one cell, tissue, or organism.

Question 9

Metabolome

Answer 9

Total number of metabolites present within one cell, tissue, or organism.

Question 10

Neonatal GI Flora

Answer 10

• Microbial colonization of GI tract starts before birth
• Meconium of full term infants not sterile
  
  • 30 genera normal to amniotic fluid, vaginal, and oral cavity
• Delivery mode & feeding methods/timing ∆ gut microbiome and immune development

Question 11

High Fiber Diet

Answer 11

High fiber diet ⇒ ↑ gut microbiota diversity ⇒ ↑ glucose control ⇒ protect against inuslin resistance & ↓ risk of obesity:

• Fermentation by gut microbes ⇒ SCFAs
  
  • Energy source for colonocytes
  • Substrate for gluconeogenesis
• Metabolism of bile acids & signaling by SCFAs ⇒ production of glucagon-like peptide 1
  
  • ⊕ insulin
  • ⊖ glucagon
  • ↓ gastric motility
  • ↓ hepatic glucose production
  • ↑ satiety
  • ↓ food intake

Question 12

High Saturated Fat Diet

Answer 12

Diet high in saturated fats ⇒ ↓ insulin sensitivity

• Postprandial lipidemia ⇒ chylomicron formation ⇒ ↑ LPS absorption from the gut
  
  • ↑ circulating LPS
  • ↑ low level systemic inflammation
  • ↑ insulin resistance

Question 13

TMAO Effects

Answer 13

L-carnitine and choline ⇒ trimethylamine (TMAs) ⇒ trimethylamine-n-oxide (TMAO)

• L-carnitine and choline found in red meat, eggs, dairy, and salt-water fish
• Metabolized by gut bacteria to TMAs then TMAOs
• Elevated TMAO associated with:
  
  • Insulin resistance
  • GI cancers

Question 14

Acetate Effects

Answer 14

• Nutrient-gut microbiota interactions ⇒ ↑ [acetate]
• Acetate ⇒ PNS activation
  
  • ↑ glucose-stimulated insulin secretion
  • ↑ ghrelin secretion
  • Hyperphagia
  • Obesity
  • Metabolic syndrome

Question 15

Gut Microbiota

Modification

Answer 15

Two approaches:

1. Figure out underlying mechanism first then develop therapies
2. Implement diet changes and assess effects then figure out underlying mechanisms

Question 16

Innate Immunity

Effects

Answer 16

SCFAs made by gut flora also:

• Drive bone marrow to make cells of myeloid linage
  
  • Neutrophils, monocytes, granulocytes
• ∆ macrophage functions

Question 17

Innate Lymphoid Cells

(ILCs)

Answer 17

• ILCs are lymphocytes that do not expression Ag-specific receptors
  
  • NK cells
  • ILC1, ILC2, ILC3
• React to PAMPs and DAMPs
• Activated ILCs kill or make cytokines
• Complex interactions between gut microbiome, ILCs and adaptive immune system
• Hormonal variations also ∆ these interactions
  
  • Circadian rhythm
  • Stress response

Question 18

Innate Immune Interactions

Summary

Answer 18