Module 5: Section 1C

Question 1

Normal Flora

Answer 1

• Normal flora (commensal microbes) are microorganisms that live on and in the body
• They are introduced at birth and remain relatively stable throughout life, unique to each person based on geography, health, and lifestyle

Question 2

Composition of Normal Flora

Answer 2

• Includes bacteria, fungi, and protists, and may also contain bacteriophages and viruses
• These organisms are usually harmless and part of the body’s normal microbial community

Question 3

Establishment of Microbes at Birth

Answer 3

• Bacteria are present in placental tissue, amniotic fluid, and meconium, showing the uterine environment isn’t sterile
• At birth, infants acquire microbes from the vaginal tract and mother’s gut, with gut flora forming within a day

Question 4

Factors Influencing Newborn Microbiome

Answer 4

• Newborn microbiome development depends on delivery method (vaginal vs. C-section) and diet (breast milk vs. formula)
• Other factors include gestational age, sanitation, and antibiotics
• Babies born by C-section have lower initial diversity

Question 5

Early Development of Gut Flora

Answer 5

• During the first 3 years of life, many factors shape the gut microbiota
• Alterations during this time can have lasting effects on development and overall health

Question 6

Later Development of Gut Flora

Answer 6

• After age 3, gut flora may change temporarily with health but usually returns to its normal state
• Established flora influences infection risk, metabolism, and obesity long-term

Question 7

Where you live can affect your flora

Answer 7

• Living in environments with circulating pathogens can cause new microbes to colonize the body
• These may stay harmless but can cause disease if immunity is weakened

Question 8

Skin - Commensal fungi

Answer 8

• Fungi living on our skin are made up of only a few species
• Diversity increases on our feet

Question 9

Internal - Commensal fungi

Answer 9

Inside the body on mucosal surfaces with a higher moisture content there are many different fungi genera

Question 10

Normal Fungal Flora

Answer 10

Fungi make up only ~0.1% of gut microbes and fluctuate more than bacteria because of environmental changes and their small population size

Question 11

Health Impact of Fungal Flora

Answer 11

The role of fungi in health is mostly unknown, but antibiotic use can lead to fungal overgrowth, especially Candida, causing infections

Question 12

Viruses as Commensals

Answer 12

Some viruses may exist in the body harmlessly as commensal organisms rather than pathogens, based on metagenomic studies showing many healthy people carry viral DNA

Question 13

Are Persistent Viruses Beneficial or Harmful?

Answer 13

The body can host persistent viral infections that may be neutral, protective, or harmful, but their exact role is unclear

Question 14

Example: Hepatitis C Virus

Answer 14

Hepatitis C causes a persistent liver infection that can remain asymptomatic for years before leading to cirrhosis and liver damage