Chapter 33: The Microbe-Human Ecosystem

Question 1

Humans Are Holobionts

Microbiome—all the (1).
* Microbiota—all the (2) in and on an organism.

(3)—hosts and microbes live together and evolve together.
* Each microbial niche is related to a variety of factors such as body location, age, sex, diet and environment.

Answer 1

1. genes found in one’s microbiota
2. microorganisms that live
3. Holobionts

Question 2

Microbiome Dev’s from Birth to Adulthood Dev’t of a Stable Microbiome

Microbiota community is (1).
* Begins developing at (2) and changes as we age.
* A stable community of microbes adopted by age (3).
* It is important to develop a (4) microbiome.

Answer 2

1. not static
2. birth
3. 3
4. diverse

Question 3

Early Colonization

Newborn colonization important.
* (1) provides exposure to microbes from the (2), whereas cesarean delivery provides microbe exposure from initial caretakers.

Bifidobacteria
* Transport (3) directly across their plasma membrane.
* Fermentation of these sugars provides (4) and lowers gut pH, limiting (5).

Answer 3

1. Vaginal birth
2. birth canal
3. polymeric sugars found in human breast milk
4. calories
5. pathogen growth

Question 4

Adult Human Microbiota

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: (6)

Some archaea, fungi, and viruses are also present.

Answer 4

• Actinobacteriota
• Bacteroidota
• Firmicutes
• Fusobacteriota
• Proteobacteria
• Verrucomicrobiota

Question 5

Microbiota Vary by Body Site

• (1) are normally free of microorganisms.
• (2) are constantly in contact with the environment and are colonized by various microbes.

Answer 5

1. Internal organs and tissues (that is, brain, blood, cerebrospinal fluid, muscles)
2. Surface tissues (that is, skin and mucous membranes)

Question 6

Skin

Environment:
* Slightly (1) pH.
* High concentration of (2).
* Some areas lack (3).
* Some bathed in oily lubricant (4).

Some microbes are temporarily present and are typically unable to multiply on the skin.
Three environmental niches: (5)

Answer 6

1. acidic
2. NaCl
3. moisture
4. sebum and antimicrobial peptides
5. Dry (greatest diversity), Moist, Sebaceous

Question 7

Staphylococcus epidermidis

Colonize the skin and generally nonpathogenic.
* (1) of healthy skin.

Modulate (2) gene expression, stimulating (3).
* Secreting products of fermentation called (4).
* Binding to the pattern recognition receptor (5).

(6)–inhibits growth of pathogens.

Answer 7

1. Key component
2. keratinocyte
3. antimicrobial peptide release
4. short chain fatty acids
5. TLR-2
6. Bacterial interference

Question 8

Respiratory Tract

(1)—nostrils, sinuses, pharynx, and oropharynx.
* Colonized by a diverse group of microbes.

(2)—larynx below the vocal cords, trachea, bronchi, and lungs.
* Not sterile as previously thought.

Answer 8

1. Upper respiratory tract (URT)
2. Lower respiratory tract (LRT)

Question 9

Lower Respiratory Tract

Difficult to sample lungs without (1).

Microbes are introduced principally from the (2).
* Stay temporary—expelled and replaced by new transients

Answer 9

1. contamination from upper respiratory tract
2. oropharynx

Question 10

Eye and External Ear

Eye
* Small number of bacteria are found on the (1) of the eye.
* Predominant bacterium is (2).

External ear
* Similar to (3), with nonpathogenic staphylococci and Corynebacterium spp. predominating.

Answer 10

1. conjunctiva
2. Staphylococcus epidermidis
3. skin flora

Question 11

Mouth

Soon after birth, the mouth is colonized by microorganisms from (1).

(2) become dominant due to the anoxic nature of the space between the teeth and gums.

As teeth grow, Streptococcus parasanguis and S. mutans attach to enamel surfaces; S. salivarius attaches to the buccal (that is, inside the cheeks) and gum epithelial surfaces and colonizes the saliva.
* Produce a (3) that enable them to attach to oral surfaces.
* Contribute to dental plaque, caries, gingivitis, and periodontal disease.

Answer 11

1. the surrounding environment
2. Anaerobes (Porphyromonas, Prevotella, and Fusobacterium spp.)
3. glycocalyx and various other adherence factors

Question 12

Stomach

Most microbes killed by acidic conditions.
* (1) can survive.

Microorganisms may survive:
* If they pass through stomach (2).
* If ingested with food particles and are (3).

Answer 12

1. Streptococcus, Staphylococcus, Lactobacillus, Peptostreptococcus spp., and yeasts such as Candida spp.
2. very quickly
3. resistant to gastric pH

Question 13

Small Intestine

Divided into three areas:
* (1)—contains few organisms due to stomach acid, bile, and pancreatic secretions; Gram-positive bacteria comprise most of the microbiota.
* (2)—Enterococcus faecalis, lactobacilli, diphtheroids, and the yeast Candida albicans found.
* (3)—flora similar to that in colon; pH becomes more alkaline; anaerobic Gram-negative bacteria and members of the family Enterobacteriaceae become established.

Answer 13

1. Duodenum
2. Jejunum
3. Ileum

Question 14

Large Intestine (Colon)

• One of the most (1) microbial ecosystems on Earth.
• Collectively the gut microbiome has (2) roles.

Answer 14

1. densely packed
2. metabolic, immunological, and endocrine

Question 15

A Functional Core Microbiome Is Required for Host Homeostasis

()
Microbes that provide the host with a suite of activities required for health and homeostasis.
* Provision of vitamin K by E. coli.
* Emerging role of gut microbiota in human behavior.
* Rapidly advancing field.

Answer 15

Functional Core Microbiome

Question 16

Host Metabolism

Gut microbiota converts food into calories that we can use.

Overweight people:
* Higher concentrations of gut bacteria belonging to the phylum (1) compared to bacteria belonging to the phylum (2).
* Several other gut microbiota population changes.

Answer 16

1. Firmicutes
2. Bacteroidota
   (Firmicutes > Bacteroidota)

Question 17

Impact of Fermentation End Products on Host Metabolism

Bacteria ferment monomers into short chain fatty acids, some of which promote weight gain.

Has refocused attention from the individual species in the gut microbiome to the ()

Answer 17

metabolome (products these microorganisms secrete).

Question 18

Immunity

(1) disrupt the gut microbial community.
* Following (1) treatment, people are at higher risk of (2).
* (3)—based on competitive exclusion.

Microbiome releases (4) that target pathogens.

Answer 18

1. Antibiotics
2. GI tract infections
3. Colonization resistance
4. toxic peptides

Question 19

Microbiome Sig’s Influence Immune Cell Func @ Sites Distant from the Gut

Germ-free mice discovered to have () that mature in the bone marrow.

Answer 19

limited development of white blood cells

Question 20

Gut Microbiota Metabolites Regulate Inflammation

• (1)—how microbes reside in our gut without an overwhelming inflammatory response.
• (2), which produce the anti-inflammatory cytokine IL-10.

Answer 20

1. Mucosal tolerance
2. Balance between pro-inflammatory cells

Question 21

Gut Microbiota Affects Central Nervous System

Specific behavioral traits (that is, inquisitiveness, sociability) and feelings (that is, anxiety, depression) differ when comparing GF mice and conventional mice.
* Influence is heritable.

We can predict three ways the
microbiome can influence the CNS:
* Microbiome impacts the (1).
* Direct pathway from gut to brain (2) which transmit signals to the brain via the vagus nerve.
* (3) cross the blood brain barrier.

Answer 21

1. immune system
2. through nerves in GI tract
3. soluble microbial products

Question 22

Metabolic Syndrome

Condition characterized by at least three of the following:
(1-5)

Associated with chronic, low-level (6).
* Linked to the microbiome as explained by (7).

Answer 22

1-5:
* Large waist circumference.
* High blood triglyceride level.
* High blood pressure.
* Elevated low-density lipoprotein.
* High fasting blood glucose levels.

6. inflammation
7. metabolic endotoxemia

Question 23

Cardiovascular Disease

Diet consumed by a person with cardiovascular disease: (1)
* Little (2) for gut microbes to produce anti-inflammatory SCFAs.
* Promotes growth of a “meat-eating” microbial population that metabolizes (3) resulting in the production of (4).
* (4) is absorbed into the bloodstream, travels to the liver where it is enzymatically oxidized by liver cells to (5).
* Acceleration of (6).

Answer 23

1. lots of red meat and high-fat foods.
2. fiber
3. L-carnitine and phosphatidylcholine
4. trimethylamine (TMA)
5. trimethylamine N-oxide
6. atherosclerosis

Question 24

Cancer

Microbes are involved in about 20% of malignancies.
* Certain viruses cause host cells to become cancerous.
* Alter the host cell cycle to (1) and prevent host cells from (2), thereby increasing mutation rates.
* (3) dysregulate host cell cycling.
* Bacteria can be involved in metastasis of tumors to distant sites.
* Many cancers linked to microorganisms are driven by the inflammatory state associated with (4).

Answer 24

1. favor proliferation
2. repairing DNA damage
3. Helicobacter pylori
4. dysbiosis

Question 25

# Microbiome Manipulation Can Be Therapeutic (1) “Live microorganisms, which, when administered in adequate amounts, confer a health benefit to the host”. * U.S. FDA does not regulate (1) foods and supplements, so claimed health benefits have not been rigorously tested. (2)—foods or supplements that include both a (3) and a (1). * (3)—compound(s) added to enhance the colonization and positive health benefits of probiotic microbes.

Answer 25

1. Probiotics 2. Synbiotics 3. Prebiotic

Question 26

# Development of a Probiotic Product Difficult to control the uniformity and effectiveness of microbes as therapeutic agents than a drug with unique chemical structure. () * Cattle that consume feed containing this microbe appear to carry less E. coli. * Easier to make beef that meets quality standards.

Answer 26

Lactobacillus acidophilus