208 ◾ Fundamental Food Microbiology
carbohydrate metabolism, and stress response. This information can then be used to better understand signaling processes among gut microbes and between intestinal cells, food components,
microbial metabolic products, and mechanisms of beneficial actions of probiotic bacteria. Finally,
they will help design better desirable gut bacteria or specific strains for specific beneficial effects.
Conclusion
Although fermented foods and some lactic acid bacteria have been considered to help to normalize intestinal microbial ecosystems, there are doubts resulting from differences in results. These
are a result of improper uses of bacteria that have not been tested by well-designed studies by
well-experienced research groups. Currently, standards of identity of beneficial intestinal bacteria
are being advocated to change the myths to reality. In the future, genome sequence information
will help better understand the interactions of food, intestinal systems, and microbial species and
strains and use them effectively.
QUESTIONS
1. Discuss the sequential establishment of GI flora in humans from birth to two years of age.
How does the predominant flora differ between breast-fed and formula-fed babies?
2. Discuss the following terms with examples: indigenous bacteria, transient bacteria, beneficial bacteria, and undesirable bacteria in the GI tract of humans.
3. List the important characteristics of beneficial bacteria present in the GI tract. Where are
they present? What are some of the antibacterial substances they produce?
4. List the factors that could adversely affect the presence of beneficial bacteria in the human
GI tract.
5. What is lactose intolerance? Explain the possible mechanisms by which consumption of
some fermented dairy products or live cells of beneficial intestinal bacteria can help overcome this problem.
6. How can beneficial intestinal bacteria or some fermented foods possibly reduce serum cholesterol levels?
7. “Beneficial GI tract bacteria may be effective in reducing colon cancer and enteric diseases.”
What is the basis of this suggestion?
8. Experimental data do not always support the health benefits from the consumption of fermented foods and live cells of beneficial intestinal bacteria. This can be a result of wide differences in experimental methods used. If you are planning to conduct such a study, what
are some of the experimental factors you should consider?
9. Discuss advantages and disadvantages associated with bioengineered probiotics.
10. Describe how lactic acid bacteria are used as a vaccine carrier and what are the potential
benefits of such an approach?
References
1. Fuller, R., Probiotics in man and animals, J. Appl. Bacteriol., 66, 365–378, 1989.
2. Sekirov, I., Russell, S.L., Antunes, L.C.M., and Finlay, B.B., Gut microbiota in health and disease,
Physiol. Rev., 90, 859–904, 2010.
carbohydrate metabolism, and stress response. This information can then be used to better understand signaling processes among gut microbes and between intestinal cells, food components,
microbial metabolic products, and mechanisms of beneficial actions of probiotic bacteria. Finally,
they will help design better desirable gut bacteria or specific strains for specific beneficial effects.
Conclusion
Although fermented foods and some lactic acid bacteria have been considered to help to normalize intestinal microbial ecosystems, there are doubts resulting from differences in results. These
are a result of improper uses of bacteria that have not been tested by well-designed studies by
well-experienced research groups. Currently, standards of identity of beneficial intestinal bacteria
are being advocated to change the myths to reality. In the future, genome sequence information
will help better understand the interactions of food, intestinal systems, and microbial species and
strains and use them effectively.
QUESTIONS
1. Discuss the sequential establishment of GI flora in humans from birth to two years of age.
How does the predominant flora differ between breast-fed and formula-fed babies?
2. Discuss the following terms with examples: indigenous bacteria, transient bacteria, beneficial bacteria, and undesirable bacteria in the GI tract of humans.
3. List the important characteristics of beneficial bacteria present in the GI tract. Where are
they present? What are some of the antibacterial substances they produce?
4. List the factors that could adversely affect the presence of beneficial bacteria in the human
GI tract.
5. What is lactose intolerance? Explain the possible mechanisms by which consumption of
some fermented dairy products or live cells of beneficial intestinal bacteria can help overcome this problem.
6. How can beneficial intestinal bacteria or some fermented foods possibly reduce serum cholesterol levels?
7. “Beneficial GI tract bacteria may be effective in reducing colon cancer and enteric diseases.”
What is the basis of this suggestion?
8. Experimental data do not always support the health benefits from the consumption of fermented foods and live cells of beneficial intestinal bacteria. This can be a result of wide differences in experimental methods used. If you are planning to conduct such a study, what
are some of the experimental factors you should consider?
9. Discuss advantages and disadvantages associated with bioengineered probiotics.
10. Describe how lactic acid bacteria are used as a vaccine carrier and what are the potential
benefits of such an approach?
References
1. Fuller, R., Probiotics in man and animals, J. Appl. Bacteriol., 66, 365–378, 1989.
2. Sekirov, I., Russell, S.L., Antunes, L.C.M., and Finlay, B.B., Gut microbiota in health and disease,
Physiol. Rev., 90, 859–904, 2010.