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Chapter 5
Microbial Growth
Characteristics
introduction
Microorganisms grow or multiply in numbers when exposed to a favorable environment, such as
food. Their growth is associated with food spoilage, foodborne diseases, and food bioprocessing.
Growth is also important in isolating an unknown microbial strain involved in food spoilage,
foodborne diseases, or food bioprocessing in pure form and studying its morphological, physiological, biochemical, and genetic characteristics in order to design methods to control or stimulate
its growth in food, destroy it, or improve its genetic makeup for better use.
Microbial Reproduction or Growth
Binary Fission
An increase in the number or mass of vegetative cells of bacteria, yeasts, and molds is customarily used to reflect growth for microorganisms. Bacteria reproduce by a process called transverse
binary fission or, simply, binary fission. The process includes several steps, such as DNA replication
and separation, partition between the DNA, invagination and septum formation of a wall, and
cell separation. In this process, one cell asexually divides into two cells, each an essentially true
replica of the original cell. However, when growing for a long time, the population from a single
cell may contain a few variant cells. In bacteria, a form of sexual recombination can occur that
involves transfer of genetic materials from a donor to a recipient cell (e.g., conjugation). However,
this is quite different from sexual reproduction, which is facilitated through the union of two cells
(gametes) of opposite mating type. 1,2
A bacterial cell has a specific surface area-to-volume (s/v) ratio. A newly divided cell has a higher
(s/v) ratio, which helps in the rapid transport of nutrients from the environment. A young cell predominantly uses nutrients to synthesize energy and cellular components, leading to an increase in
cell size. As the cell size increases, the (s/v) ratio decreases, which adversely affects the transport of
Chapter 5
Microbial Growth
Characteristics
introduction
Microorganisms grow or multiply in numbers when exposed to a favorable environment, such as
food. Their growth is associated with food spoilage, foodborne diseases, and food bioprocessing.
Growth is also important in isolating an unknown microbial strain involved in food spoilage,
foodborne diseases, or food bioprocessing in pure form and studying its morphological, physiological, biochemical, and genetic characteristics in order to design methods to control or stimulate
its growth in food, destroy it, or improve its genetic makeup for better use.
Microbial Reproduction or Growth
Binary Fission
An increase in the number or mass of vegetative cells of bacteria, yeasts, and molds is customarily used to reflect growth for microorganisms. Bacteria reproduce by a process called transverse
binary fission or, simply, binary fission. The process includes several steps, such as DNA replication
and separation, partition between the DNA, invagination and septum formation of a wall, and
cell separation. In this process, one cell asexually divides into two cells, each an essentially true
replica of the original cell. However, when growing for a long time, the population from a single
cell may contain a few variant cells. In bacteria, a form of sexual recombination can occur that
involves transfer of genetic materials from a donor to a recipient cell (e.g., conjugation). However,
this is quite different from sexual reproduction, which is facilitated through the union of two cells
(gametes) of opposite mating type. 1,2
A bacterial cell has a specific surface area-to-volume (s/v) ratio. A newly divided cell has a higher
(s/v) ratio, which helps in the rapid transport of nutrients from the environment. A young cell predominantly uses nutrients to synthesize energy and cellular components, leading to an increase in
cell size. As the cell size increases, the (s/v) ratio decreases, which adversely affects the transport of