their metabolism’s products. In most cases, the mutual relationship is rather weak.
Endocommensals typically are microscopic organisms that mostly colonize gastrointestinal systems of terrestrial animals and humans, but there certainly also are
endocommensals of aquatic animals and some endocommensals colonize plants.
The so-called endocommensal protozoa can feed on bacteria in the intestinal tract.
Endocommensal organisms are dependent entirely on the inner environment of the
host and they are unable, with small exceptions, to live independently in the open
environment, where they would quickly perish.
Some interesting and remarkable examples of commensalism include the fact that
commensalism can also develop such that an unaffected population of microbes,
during its growth, adjusts its surrounding environment in such a way that another
population benefits from it because the modified environment is more suitable for
requirements of the second population. For example, when a population of facultatively anaerobic microorganisms uses oxygen, it lowers the surrounding oxygen
content and thus creates an environment more suitable for an obligatory anaerobe.
Thus, in this case the obligatory anaerobe benefits by the metabolic activity of the
facultative anaerobe. The production of growth factors creates another platform for
many commensal relations between microbial populations. A certain microbial
populations may synthetize and secrete growth factors (for instance, amino acids
and vitamins) that can be utilized by other microbial populations. For example,
Empedobacter brevis secretes an amino acid, cysteine, which Legionella
pneumophilla in the water environment uses for its multiplication.
Another type of commensalism among populations is the conversion of organic
molecules by one population into a substrate suitable for another population. For
example, certain fungi produce extracellular enzymes that can convert complex
polymeric compounds, such as cellulose, into smaller substances and even into
glucose. These simpler compounds can then be used by other microorganisms for
their nutrition when those other microorganisms do not possess their own enzymes
for degradation of the complex organic molecules.
Transformation of insoluble compounds into soluble ones, and the subsequent
conversion of soluble substances into gaseous compounds, forms a basis for certain
types of commensal relationships in which gaseous substances can then be beneficial
for other microbial populations. For instance, methane produced by bacterial
populations in sediments can be useful to methane-oxidizing bacteria in a water
environment. Under certain conditions bacteria of the genus Desulfovibrio can
supply compounds to Methanobacterium which then is capable of using those
compounds to reduce carbon dioxide to methane.
Also, an activity of one microbial population can release a compound without its
chemical transformation for use by another population. As an example, it is possible
to denote an acid production by one microbial population, which can release
compounds bound to soil particles or otherwise not accessible to the other population. Such desorption processes are most likely frequent in the soil where many
substances are bound either to mineral particles or to a humic substance. Entylia uses
a form of commensalism where the commensal is found directly in the host’s body
cavity without causing any harmful or negative effect to the host. For instance,
246
V. Klaban
Endocommensals typically are microscopic organisms that mostly colonize gastrointestinal systems of terrestrial animals and humans, but there certainly also are
endocommensals of aquatic animals and some endocommensals colonize plants.
The so-called endocommensal protozoa can feed on bacteria in the intestinal tract.
Endocommensal organisms are dependent entirely on the inner environment of the
host and they are unable, with small exceptions, to live independently in the open
environment, where they would quickly perish.
Some interesting and remarkable examples of commensalism include the fact that
commensalism can also develop such that an unaffected population of microbes,
during its growth, adjusts its surrounding environment in such a way that another
population benefits from it because the modified environment is more suitable for
requirements of the second population. For example, when a population of facultatively anaerobic microorganisms uses oxygen, it lowers the surrounding oxygen
content and thus creates an environment more suitable for an obligatory anaerobe.
Thus, in this case the obligatory anaerobe benefits by the metabolic activity of the
facultative anaerobe. The production of growth factors creates another platform for
many commensal relations between microbial populations. A certain microbial
populations may synthetize and secrete growth factors (for instance, amino acids
and vitamins) that can be utilized by other microbial populations. For example,
Empedobacter brevis secretes an amino acid, cysteine, which Legionella
pneumophilla in the water environment uses for its multiplication.
Another type of commensalism among populations is the conversion of organic
molecules by one population into a substrate suitable for another population. For
example, certain fungi produce extracellular enzymes that can convert complex
polymeric compounds, such as cellulose, into smaller substances and even into
glucose. These simpler compounds can then be used by other microorganisms for
their nutrition when those other microorganisms do not possess their own enzymes
for degradation of the complex organic molecules.
Transformation of insoluble compounds into soluble ones, and the subsequent
conversion of soluble substances into gaseous compounds, forms a basis for certain
types of commensal relationships in which gaseous substances can then be beneficial
for other microbial populations. For instance, methane produced by bacterial
populations in sediments can be useful to methane-oxidizing bacteria in a water
environment. Under certain conditions bacteria of the genus Desulfovibrio can
supply compounds to Methanobacterium which then is capable of using those
compounds to reduce carbon dioxide to methane.
Also, an activity of one microbial population can release a compound without its
chemical transformation for use by another population. As an example, it is possible
to denote an acid production by one microbial population, which can release
compounds bound to soil particles or otherwise not accessible to the other population. Such desorption processes are most likely frequent in the soil where many
substances are bound either to mineral particles or to a humic substance. Entylia uses
a form of commensalism where the commensal is found directly in the host’s body
cavity without causing any harmful or negative effect to the host. For instance,
246
V. Klaban