How do gut flora protect against pathogens through competition for attachment sites?

Commensal bacteria occupy attachment sites on the gut lining, preventing pathogens from adhering and colonising.

What antimicrobial substances can gut flora produce to protect against infection?

Gut flora can produce antimicrobial substances such as bacteriocins and organic acids that inhibit or kill pathogenic micro-organisms.

How do skin flora protect against pathogenic colonisation?

Skin flora protect through competitive exclusion (occupying space and using nutrients) and by maintaining conditions such as low pH that are unfavourable to pathogens.

Why are exponential functions useful when modelling bacterial population growth?

Bacterial populations grow by binary fission, doubling at regular intervals, which produces exponential growth that is best described using exponential functions.

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Immunity, Infection and Forensics

The body's barriers, and modelling bacterial growth

3 things to know
Papers 1 and 3

Overview

Recall questions on the skin, stomach acid and gut and skin flora, and on using exponential and logarithmic scales for bacterial growth.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Key term

Why are logarithmic scales useful when representing microbial growth data?

Key term

Explain how stomach acid acts as a chemical barrier against pathogens.

Key term

How do gut flora protect against infection by competing for nutrients?

Questions from this subtopic

Each one with the model answer underneath.

1
Explain how stomach acid acts as a chemical barrier against pathogens.
Model answer
Hydrochloric acid in the stomach creates a low pH environment that denatures pathogen proteins and kills most ingested micro-organisms.
2
How do gut flora protect against infection by competing for nutrients?
Model answer
Commensal bacteria in the intestines use available nutrients, reducing the resources available for pathogenic bacteria to grow.
3
How do gut flora protect against pathogens through competition for attachment sites?
Model answer
Commensal bacteria occupy attachment sites on the gut lining, preventing pathogens from adhering and colonising.
4
What antimicrobial substances can gut flora produce to protect against infection?
Model answer
Gut flora can produce antimicrobial substances such as bacteriocins and organic acids that inhibit or kill pathogenic micro-organisms.
5
How do skin flora protect against pathogenic colonisation?
Model answer
Skin flora protect through competitive exclusion (occupying space and using nutrients) and by maintaining conditions such as low pH that are unfavourable to pathogens.
6
Why are exponential functions useful when modelling bacterial population growth?
Model answer
Bacterial populations grow by binary fission, doubling at regular intervals, which produces exponential growth that is best described using exponential functions.

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