30 ◾ Fundamental Food Microbiology
Fecal Coliforms
Mainly Escherichia coli is included in this group. They are also used as an index of sanitation.
Enteric Pathogens
Pathogenic Salmonella, Shigella, Campylobacter, Yersinia, Escherichia, Vibrio, hepatitis A, and others that can cause gastrointestinal infection are included in this group.
Because of the importance of these bacterial groups in food, many laboratory methods are
designed to detect a specific group instead of a specific genus or species. Similarly, control methods
are sometimes designed to destroy or prevent growth of a specific group.
Conclusion
Two major aspects have been discussed in this chapter: the nomenclature system of bacteria,
which is rapidly changing because of the development of new molecular biology techniques, and
the morphological and physiological characteristics of the microorganisms important in food. A
food microbiologist should be knowledgeable about these facets. Chapter 3 discusses the sources
of these microorganisms in food.
QUESTIONS
1. List five methods that are used in the classification of bacteria. Why are nucleotide sequences
in 16S rRNA used as an important technique in the classification?
2. Explain the following terms and give one example for each in relation to bacterial nomenclature: (a) family, (b) genus, (c) species, (d) subspecies, and (e) biovar (use scientific method
in the examples). Give the plural of Lactobacillus, Staphylococcus, Enterococcus, Leuconostoc,
Listeria, and Salmonella.
3. List the general differences in the morphology of yeasts, molds, bacteria, and bacteriophages
important in food.
4. List the differences in the chemical nature and function of cell wall structures between
Gram-positive and Gram-negative bacteria. How does this help determine the Gram characteristics of an unknown bacterial isolate?
5. List four species of molds and two species of yeasts most important in food.
6. List four protozoan species that are responsible for water and foodborne outbreaks.
7. Discuss the importance of bacteriophages in food. Briefly explain how prions are different
from the bacteriophages.
8. List two genera from each of the following groups: (a) Gram-negative aerobic rods, (b) Gramnegative facultative anaerobic rods, (c) Gram-positive cocci, (d) Gram-positive endosporeforming rods, and (e) Gram-positive nonsporulating rods.
9. Briefly mention the common characteristics used to group bacterial genera or species in the
following groups and give one example of genus for each: (a) lactic acid bacteria, (b) coliforms, (c) proteolytic bacteria, (d) psychrotrophic bacteria, and (e) enteric pathogens.
Fecal Coliforms
Mainly Escherichia coli is included in this group. They are also used as an index of sanitation.
Enteric Pathogens
Pathogenic Salmonella, Shigella, Campylobacter, Yersinia, Escherichia, Vibrio, hepatitis A, and others that can cause gastrointestinal infection are included in this group.
Because of the importance of these bacterial groups in food, many laboratory methods are
designed to detect a specific group instead of a specific genus or species. Similarly, control methods
are sometimes designed to destroy or prevent growth of a specific group.
Conclusion
Two major aspects have been discussed in this chapter: the nomenclature system of bacteria,
which is rapidly changing because of the development of new molecular biology techniques, and
the morphological and physiological characteristics of the microorganisms important in food. A
food microbiologist should be knowledgeable about these facets. Chapter 3 discusses the sources
of these microorganisms in food.
QUESTIONS
1. List five methods that are used in the classification of bacteria. Why are nucleotide sequences
in 16S rRNA used as an important technique in the classification?
2. Explain the following terms and give one example for each in relation to bacterial nomenclature: (a) family, (b) genus, (c) species, (d) subspecies, and (e) biovar (use scientific method
in the examples). Give the plural of Lactobacillus, Staphylococcus, Enterococcus, Leuconostoc,
Listeria, and Salmonella.
3. List the general differences in the morphology of yeasts, molds, bacteria, and bacteriophages
important in food.
4. List the differences in the chemical nature and function of cell wall structures between
Gram-positive and Gram-negative bacteria. How does this help determine the Gram characteristics of an unknown bacterial isolate?
5. List four species of molds and two species of yeasts most important in food.
6. List four protozoan species that are responsible for water and foodborne outbreaks.
7. Discuss the importance of bacteriophages in food. Briefly explain how prions are different
from the bacteriophages.
8. List two genera from each of the following groups: (a) Gram-negative aerobic rods, (b) Gramnegative facultative anaerobic rods, (c) Gram-positive cocci, (d) Gram-positive endosporeforming rods, and (e) Gram-positive nonsporulating rods.
9. Briefly mention the common characteristics used to group bacterial genera or species in the
following groups and give one example of genus for each: (a) lactic acid bacteria, (b) coliforms, (c) proteolytic bacteria, (d) psychrotrophic bacteria, and (e) enteric pathogens.