Human Microbiome

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Questions and Answers

What is the primary reason for the skin being a hostile environment for microorganisms?

High pH

Presence of organic acids

Low water activity (correct)

Low salt concentrations

Which type of bacteria is more likely to be desiccation resistant and halotolerant?

Gram positive bacteria (correct)

Aerobic bacteria

Anaerobic bacteria

Gram negative bacteria

What is the primary function of lipases produced by P.acne?

Synthesizing glycerol

Breaking down proteins

Hydrolyzing carbohydrates

Using triglycerides as a substrate to produce free fatty acids (correct)

What is the primary reason for the colonization of the intestines?

Presence of a community of bacteria in the mucosal layer Signup and view all the answers

Which type of bacteria is predominantly found in the skin microbiota?

Gram positive bacteria Signup and view all the answers

What is the primary characteristic of the microbiota found in dental plaque?

Complex interplay between different species Signup and view all the answers

What is the primary function of H.pylori in the stomach?

Colonizing the mucosal layer Signup and view all the answers

What happens to the microbiome as you move further into the small intestine?

It becomes more complex Signup and view all the answers

What is the approximate number of CFU/faeces in the large intestine?

10^9-10^12 Signup and view all the answers

What is the role of some species of microbiota in human nutrition?

To break down complex carbohydrates Signup and view all the answers

What happens to the microbiome when the diet is high in protein and animal fat?

It becomes enriched with Bacteroides Signup and view all the answers

Why can E. coli grow well in mucus but not in faeces?

Because it can catabolise gluconate Signup and view all the answers

What is the effect of disrupting the normal microbiota?

It allows pathogens to grow Signup and view all the answers

What is the effect of a high carbohydrate diet on the microbiome?

It becomes enriched with Prevotella Signup and view all the answers

What is the primary mechanism by which P.acne produces free fatty acids?

By hydrolyzing triglycerides using lipases Signup and view all the answers

Which of the following factors contributes to the hostile environment of the skin for microorganisms?

Acidic pH, desiccation, and high salt concentration Signup and view all the answers

What is the primary reason why Gram-positive bacteria are more likely to colonize the skin?

Because they are more halotolerant and desiccation-resistant Signup and view all the answers

Which of the following best describes the community of bacteria in dental plaque?

A highly complex community of multiple species Signup and view all the answers

What is the primary function of the community of bacteria residing in the mucosal layer of the stomach?

To protect against infection by pathogens Signup and view all the answers

What is the approximate surface area of the skin that is populated by microorganisms?

2M^2 Signup and view all the answers

What is the estimated number of microorganisms found on the skin?

10^12 Signup and view all the answers

What is the primary reason why the duodenum and jejunum allow for limited microbial growth?

All of the above Signup and view all the answers

What is the primary benefit of the breakdown of complex carbohydrates by microbiota in the large intestine?

Support of the host's nutritional needs Signup and view all the answers

What is the primary consequence of a disrupted normal microbiota?

Allowing pathogens to grow Signup and view all the answers

What is the primary reason why E. coli grows poorly in faeces?

Lack of gluconate in faeces Signup and view all the answers

What is the primary difference between the microbiota of the small intestine and the large intestine?

The large intestine has a more complex microbiota Signup and view all the answers

What is the primary effect of breast milk on the microbiota?

Encouraging the growth of certain populations of microbiota Signup and view all the answers

What is the primary characteristic of the microbiota in the large intestine?

It is highly complex and anaerobic Signup and view all the answers

Study Notes

Microbiome Overview

Defined as a host-associated community of commensal, symbiotic, and pathogenic microorganisms.
Also known as microbiota or microbial flora.

Skin Microbiome

Adults possess approximately 2 m² of skin inhabited by around 10¹² microorganisms.
Skin acts as a hostile environment: desiccation, acidic pH, high salt content, low water activity, and presence of organic acids.
Despite these challenges, colonization occurs, primarily by Gram-positive bacteria, which are desiccation and halotolerant.
Key skin microbiota includes Corynebacteria, Propionibacteria, Staphylococci, and Candida.
Propionibacterium acnes produces lipases that convert triglycerides into free fatty acids.

Oral Microbiome

Dental plaque represents a complex community of bacteria with intricate interspecies interactions.
Only Streptococcus mutans is a direct contributor to dental caries.

Gastric Microbiome

The stomach's low pH is inhospitable to many, yet bacteria can reside in the mucosal layer.
Helicobacter pylori is a non-pathogenic bacterium that can cause gastric ulcers.

Intestinal Microbiome

The duodenum and jejunum support limited microbial growth due to pancreatic secretions and bile salts, with pH stabilizing around 8.
The complexity of the microbiome increases further down the small intestine.
The large intestine contains a highly diverse microbiome, with approximately 10⁹ to 10¹² colony-forming units (cfu) per feces.
This anaerobic environment is home to obligate and facultative anaerobes, with some species essential for human nutrition.

Functions of the Microbiome

Essential roles include the breakdown of complex carbohydrates and suppression of pathogens.
Disruption of the normal microbiota can facilitate pathogen growth.

Dietary Impact on Microbiome

Diets high in protein and animal fat favor Bacteroides species.
Diets rich in carbohydrates lead to an increase in Prevotella populations.
Breast milk supports the growth of specific microbiota populations.

Escherichia coli (E. coli) Behavior

E. coli grows poorly in feces but thrives in mucus by utilizing gluconate.
E. coli's growth is influenced more by secretions rather than food intake.

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Description

Learn about the human microbiome, a community of microorganisms living in and on the human body. Explore the populations of microorganisms in different areas of the body, including the skin, mouth, genitourinary tract, and intestines. Discover the factors that shape the microbiome and its importance for human health.