25.2.2.1 Antibiosis
Ever since the discovery of penicillin, humans have successfully developed effective
therapeutic techniques against pathogens based on the use of antibiotics. However,
adaptation of this miracle weapon has immediately caused the emergence of
antibiotic-resistant causative agents. A detailed study on resistance mechanisms
has revealed the occurrence of surprising strategies that permit the growth of the
specific organism targeted, even in the presence of the antibiotic (Blair et al. 2015).
Such resistance mechanisms include degradation, modification, and elimination of
the corresponding antibiotic and the formation of a backup mechanism for
circumventing the pathway inhibited by the antibiotic. The genes directing the
expression of those resistant mechanisms are even transferred between different
taxonomic groups by mobile genetic elements, such as conjugative plasmids and
transposons.
The occurrence of the abovementioned serious problem in the clinical area is an
artifact. This is caused by human activity, which is administering a great amount of
antibiotics to stop the growth of a specific bacterium. However, this phenomenon
demonstrates that the natural microbial community retains the potential to respond
even to such an unusual impact and recovers eventually.
Compounds exhibiting bactericidal activity are widely produced by actinomycetes, a group of filamentous bacteria represented by the genus Streptomyces. Since
Selman Waksman’s discovery of streptomycin, an effective agent against tuberculosis, many biologically active substances have been isolated from cultures of this
group of bacteria and used for medicinal treatment. The term “antibiotics” was
defined by Waksman as “a microbial product” that has the ability to inhibit the
growth of certain bacteria (Davies 2006).
Although there is a discussion whether antibiotics actually serve as antibiotics in
the natural environment, one major possibility is that these compounds actually
serve as weapons that protect producer organisms from invasion by other microorganisms (Ueda and Beppu 2017). It may also make the producer dominant in
nutritional competition by killing or inactivating competitors.
Competition is one of the major modes of interactions. It appears to have a
negative effect on the persistency of a diverged community, because it makes
organisms exclude each other. However, competition stimulates the development
of various abilities and strategies to survive. The toughness of living organisms is
established and maintained, at least in part, by being exposed to a tensed situation, as
observed for various human activities, such as business, sports, and even arts. Thus,
competition supports a rigid community structure.
25.2.2.2 Symbiosis
Symbiosis usually refers to an association that benefits at least one of the interacting
organisms. Symbiotic interactions have been widely observed within the mutualistic
25 Invisible Interactions between Microorganisms
531
Ever since the discovery of penicillin, humans have successfully developed effective
therapeutic techniques against pathogens based on the use of antibiotics. However,
adaptation of this miracle weapon has immediately caused the emergence of
antibiotic-resistant causative agents. A detailed study on resistance mechanisms
has revealed the occurrence of surprising strategies that permit the growth of the
specific organism targeted, even in the presence of the antibiotic (Blair et al. 2015).
Such resistance mechanisms include degradation, modification, and elimination of
the corresponding antibiotic and the formation of a backup mechanism for
circumventing the pathway inhibited by the antibiotic. The genes directing the
expression of those resistant mechanisms are even transferred between different
taxonomic groups by mobile genetic elements, such as conjugative plasmids and
transposons.
The occurrence of the abovementioned serious problem in the clinical area is an
artifact. This is caused by human activity, which is administering a great amount of
antibiotics to stop the growth of a specific bacterium. However, this phenomenon
demonstrates that the natural microbial community retains the potential to respond
even to such an unusual impact and recovers eventually.
Compounds exhibiting bactericidal activity are widely produced by actinomycetes, a group of filamentous bacteria represented by the genus Streptomyces. Since
Selman Waksman’s discovery of streptomycin, an effective agent against tuberculosis, many biologically active substances have been isolated from cultures of this
group of bacteria and used for medicinal treatment. The term “antibiotics” was
defined by Waksman as “a microbial product” that has the ability to inhibit the
growth of certain bacteria (Davies 2006).
Although there is a discussion whether antibiotics actually serve as antibiotics in
the natural environment, one major possibility is that these compounds actually
serve as weapons that protect producer organisms from invasion by other microorganisms (Ueda and Beppu 2017). It may also make the producer dominant in
nutritional competition by killing or inactivating competitors.
Competition is one of the major modes of interactions. It appears to have a
negative effect on the persistency of a diverged community, because it makes
organisms exclude each other. However, competition stimulates the development
of various abilities and strategies to survive. The toughness of living organisms is
established and maintained, at least in part, by being exposed to a tensed situation, as
observed for various human activities, such as business, sports, and even arts. Thus,
competition supports a rigid community structure.
25.2.2.2 Symbiosis
Symbiosis usually refers to an association that benefits at least one of the interacting
organisms. Symbiotic interactions have been widely observed within the mutualistic
25 Invisible Interactions between Microorganisms
531