Food Microbiology Chapter II: Intestinal Bacteria and Probiotics

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is a characteristic of Lactobacillus acidophilus?

It is a Gram-negative bacteria

It is a heterolactic fermentator

It is an obligatory homolactic fermentator (correct)

It produces only acetic acid

What is the meaning of the word 'probiotic'?

Instead of life

Against life

For life (correct)

Without life

What is a characteristic of Lactobacillus reuteri?

It is a heterolactic fermentator (correct)

It is an obligatory homolactic fermentator

It produces lactic acid and acetic acid

It produces only ethanol

What is a beneficial effect of Bifidobacterium?

It produces lactic and acetic acids Signup and view all the answers

What is a characteristic of probiotics?

They are live microorganisms that confer a health benefit Signup and view all the answers

What is a potential benefit of Lactobacillus acidophilus?

It has an antibacterial effect on Gram-positive bacteria Signup and view all the answers

What is the beneficial effect of probiotics on lactose-intolerant individuals?

Hydrolyzing lactose molecules in the small intestine Signup and view all the answers

How do probiotics reduce serum cholesterol levels?

By de-conjugating bile salts and preventing their reabsorption in the liver Signup and view all the answers

What is the role of beneficial intestinal bacteria in preventing colon cancer?

Reducing the production of enzymes that activate pro-carcinogens Signup and view all the answers

What is the beneficial effect of Lactobacillus acidophilus on lactose metabolism?

Supplying lactase in the small intestine Signup and view all the answers

What is the role of Bifidobacterium in gut health?

Controlling the growth of undesirable bacteria in the colon Signup and view all the answers

What is the beneficial effect of probiotics on enteric infections?

Preventing the invasion and growth of enteric pathogens Signup and view all the answers

What is the beneficial effect of probiotics on immune response?

Stimulating the production of anti-inflammatory cytokines Signup and view all the answers

What is the beneficial effect of probiotics on allergic diseases?

Suppressing the inflammatory response to food antigens Signup and view all the answers

What is an important consideration in selecting probiotic strains?

All of the above Signup and view all the answers

What is the effect of using preparations with low levels of viable cells on the beneficial effects of probiotics?

Reduced beneficial effects Signup and view all the answers

What is the approximate number of microbial species in the human gastrointestinal tract?

1000 Signup and view all the answers

What type of microorganisms are present in the upper part of the GI tract?

Aerobic microbes Signup and view all the answers

What is the main reason for the establishment of normal flora in the GI tract of infants?

Vaginal and fecal flora from the mother Signup and view all the answers

What is the characteristic of Lactobacillus acidophilus, Lactobacillus reuteri, and Bifidobacterium?

Gram-positive rods Signup and view all the answers

What is the role of Lactobacillus acidophilus, Lactobacillus reuteri, and Bifidobacterium in the GI tract?

To help in maintaining the ecological balance of GI tract microflora Signup and view all the answers

What is the significance of the presence of high numbers of Lactobacillus species in the feces?

It results from their constant removal from the small intestine Signup and view all the answers

What is the classification of Lactobacillus acidophilus, Lactobacillus reuteri, and Bifidobacterium?

Indigenous microflora Signup and view all the answers

What is the effect of age, food habits, and health conditions on the species and their levels in the GI tract?

They have a significant effect Signup and view all the answers

What is the characteristic of Lactobacillus acidophilus, Lactobacillus reuteri, and Bifidobacterium with respect to stomach acid and bile?

They are less sensitive to stomach acid and bile Signup and view all the answers

What is the significance of the dominance of Bacteroidetes, Firmicutes, and Actinobacteria in the human GI tract?

They are dominant because they are more adaptable Signup and view all the answers

Study Notes

Intestinal Bacteria and Probiotics

The human gastrointestinal (GI) tract contains over 10^14 microorganisms, which is more than the total number of human body cells, and they coexist as mutualists.
These microorganisms are metabolically diverse and active, and have a significant influence on human well-being.

Dominant Phyla in the GI Tract

The human GI tract harbors three dominant phyla: Bacteroidetes, Firmicutes, and Actinobacteria.
Approximately 1000 microbial species are present in the GI tract, but only 30-40 species constitute 95% of the population.

Microbial Counts in the GI Tract

Aerobic microbes are present in the upper part of the GI tract, while anaerobic bacteria are present in the lower part of the GI tract.
The intestine of a fetus is sterile, but at birth, it is inoculated with vaginal and fecal flora from the mother.
Subsequently, a large variety of microorganisms enter the digestive tract of infants from the environment.

Establishment of Normal Flora

The normal flora of the GI tract is established from the environment, and age, food habits, and health conditions greatly influence the species and their levels.
Lactobacillus acidophilus, Lactobacillus reuteri, and Bifidobacterium are considered the main indigenous species.

Characteristics of Beneficial Bacteria

Lactobacillus acidophilus, Lactobacillus reuteri, and Bifidobacterium are Gram-positive rods that grow under anaerobic conditions.
They are less sensitive to stomach acid and highly resistant to bile, lysozyme, and pancreatic enzymes present in the small intestine.
These species help maintain the ecological balance of the GI tract microflora by controlling the growth rate of undesirable microflora.

Benefits of Probiotics

Probiotics provide protection against enteric pathogens.
They supply enzymes to help metabolize some food nutrients, such as lactase to hydrolyze lactose.
They detoxify harmful food components and metabolites in the intestine.
They stimulate the intestinal immune system.
They improve intestinal peristaltic activity.
They reduce tumorigenesis.
They ameliorate chronic disorders.

Specific Benefits of Probiotics

Lactose hydrolysis: Probiotics can help lactose-intolerant individuals by supplying lactase in the small intestine.
Reducing serum cholesterol levels: Probiotics have been associated with low levels of serum cholesterol in humans.
Reducing colon cancer: Probiotics can reduce the production of enzymes that activate pro-carcinogens and aid in the removal of fecal material.
Preventing and controlling enteric infections: Probiotics can reduce the growth of undesirable bacteria and prevent enteric infections.
Modulating immune response: Probiotics can regulate systemic and local immune responses, especially during the development of lymphoid tissues in the gut.
Reducing allergic diseases: Probiotics can suppress inflammatory responses to food antigens and reduce allergic reactions.

Aspects to Consider

The health benefit theory of fermented foods and beneficial intestinal bacteria is controversial.
In selecting bacterial strains, considerations such as strain variation, sensitivity to stomach acids, biles, and pancreatin, viability and injury of cells, dose level, and duration are important.
The use of antibacterial substances, such as bacteriocins, can also be beneficial.

Definition of Probiotics

Probiotics are defined as live microorganisms that, when administered in adequate amounts, confer a health benefit on the host.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

This chapter covers the microbiology of the human gastrointestinal tract, including the diverse microbial community and its influence on human well-being.