achieved either by exposing the cells to cycloheximid or by exposure to the
temperature of 40
C.
It is of interest that zymocins were found only in the wine strains of S. cerevisiae.
However, their production also has been detected in other genera of yeasts, for
example, Cryptococcus, Debaryomyces, Kloeckera, Kluyveromyces, and Pichia.
Zymocins are determined genetically and are formed by yeasts containing in their
cells a special virus, the RNA of which codes for their synthesis. It is assumed that
the zymocin-forming yeasts hold a certain ecological advantage over other yeasts.
Zymocines, or rather the current killer strains, can sometimes influence negatively
even classical biotechnological processes. Such instances have been described in
beer brewing where the presence of killer strains led to a significant slowdown of the
fermenting process and at the same time, there were reports of negative sensory
qualities of the produced beer. Experiments designed to examine if the killer strains
could prevent contamination by foreign or undesirable yeasts also have been
conducted. However, quite a few disadvantages have resulted in this approach not
being followed in practical applications.
15.5 Microbial Competition
Competition is a type of interactive association between two microorganisms. There
are situations in which both species require the same nutrient or even the very same
living space for their existence. Since the nutrient exists in the environment only in a
certain quantity, the two microorganisms grow only at suboptimal speed, as they
have to share the limited resource. This type of competition is called exploitative.
Then there is interferential competition, which is direct. In many cases, it is
provoked by a greater aggressivness of behavior of some organisms, thus preventing
the other species from obtaining the necessary amount of a nutrient. It is also
possible that one type of organism displaces the other one from their common
space. This is a case of an exclusive competition. Furthermore, taken from a different
point of view, there can be interspecific competitions occurring between populations
of different species, as well as an intraspecific competition between individuals of
the same species, within a given study population.
Competition exists among all groups of organisms and it represents an important
biological regulatory mechanism in nature. It eliminates the less viable individuals.
At the same time it reduces the density of individuals in a given population. It can
contribute to the process of speciation, the formation of new and distinct species in
the course of evolution.
15 Microscopic World and the Phenomenon of Symbiosis in the Natural Environment
251
temperature of 40
C.
It is of interest that zymocins were found only in the wine strains of S. cerevisiae.
However, their production also has been detected in other genera of yeasts, for
example, Cryptococcus, Debaryomyces, Kloeckera, Kluyveromyces, and Pichia.
Zymocins are determined genetically and are formed by yeasts containing in their
cells a special virus, the RNA of which codes for their synthesis. It is assumed that
the zymocin-forming yeasts hold a certain ecological advantage over other yeasts.
Zymocines, or rather the current killer strains, can sometimes influence negatively
even classical biotechnological processes. Such instances have been described in
beer brewing where the presence of killer strains led to a significant slowdown of the
fermenting process and at the same time, there were reports of negative sensory
qualities of the produced beer. Experiments designed to examine if the killer strains
could prevent contamination by foreign or undesirable yeasts also have been
conducted. However, quite a few disadvantages have resulted in this approach not
being followed in practical applications.
15.5 Microbial Competition
Competition is a type of interactive association between two microorganisms. There
are situations in which both species require the same nutrient or even the very same
living space for their existence. Since the nutrient exists in the environment only in a
certain quantity, the two microorganisms grow only at suboptimal speed, as they
have to share the limited resource. This type of competition is called exploitative.
Then there is interferential competition, which is direct. In many cases, it is
provoked by a greater aggressivness of behavior of some organisms, thus preventing
the other species from obtaining the necessary amount of a nutrient. It is also
possible that one type of organism displaces the other one from their common
space. This is a case of an exclusive competition. Furthermore, taken from a different
point of view, there can be interspecific competitions occurring between populations
of different species, as well as an intraspecific competition between individuals of
the same species, within a given study population.
Competition exists among all groups of organisms and it represents an important
biological regulatory mechanism in nature. It eliminates the less viable individuals.
At the same time it reduces the density of individuals in a given population. It can
contribute to the process of speciation, the formation of new and distinct species in
the course of evolution.
15 Microscopic World and the Phenomenon of Symbiosis in the Natural Environment
251