15.4.1 Biosynthesis of Bacteriocins and Their Lethal Effect
In 1877 Louis Pasteur, along with Jules Francois Joubert (Pasteur and Joubert 1877)
systematically studied antagonistic interaction between bacteria. They discovered
that common bacteria such as Escherichia coli can inhibit the growth of Bacillus
anthracis (anthrax bacteria) when both of them are simultaneously inoculated into
urine, used as a culture medium.
Bacteriocins are generally stated as being either proteins or peptides, which
exhibit bactericidal effect on other closely related strains of bacteria. It appears,
however, that some bacteriocins are composed of a combination of various proteins
or are proteins with either lipid or saccharide components. Bacteriocins produced by
Gram-positive bacteria are most likely synthetized at first as prepeptides. Later a
leader peptide is separated from the rest of the prepeptide. This leader peptide then
exhibits biological activity. According to Anthony P. Pugsley (1984a, b) colicins
exhibit two main types of lethal effects. Some of them form channels in the
cytoplasmatic membrane, while others inhibit nuclease activity following their
entry into sensitive cells. However, in view of the small molecular mass of bacteriocins of Gram-positive bacteria it is assumed that they mostly affect the cellular
membranes.
Every kind of colicin is adsorbed onto a receptor molecule of the outer membrane. This phase of attack represents the first part of an interaction with sensitive
cells. It appears, though, that many bacteriocins of Gram-positive bacteria possess a
relatively small adsorption specificity. It is because the cellular wall of Grampositive bacteria allows passage of relatively large molecules that bacteriocin attack
against Gram-positive bacteria does not really require the need for a presence of
bacteriocin receptors as opposed to the outer membrane of Gram-negative cells.
Colicin production is always determined by plasmids. As stated earlier, the bestknown bacteriocins are colicins. They are produced by certain strains of Escherichia
coli and related species of the family Enterobacteriaceae. Immediately after contact
with colicin, the growth and multiplication of sensitive cells stop. Depending on the
general conditions and on the colicin type, in about 20 min the attacked rod-shaped
bacteria start to increase their volume and along with their loss of light refraction
they assume an ovoid or a spherical shape.
15.4.2 Characteristic Properties of Colicins
Colicins represent a group of antibiotic substances, which are characterized by
several common properties:
(a) All of them are either proteins or peptides.
(b) The structure of colicin molecules is coded by genes localized in special
plasmids, the so-called Col plasmids.
(c) Colicins are formed during growth of so-called colicinogenic cultures.
15 Microscopic World and the Phenomenon of Symbiosis in the Natural Environment
249
In 1877 Louis Pasteur, along with Jules Francois Joubert (Pasteur and Joubert 1877)
systematically studied antagonistic interaction between bacteria. They discovered
that common bacteria such as Escherichia coli can inhibit the growth of Bacillus
anthracis (anthrax bacteria) when both of them are simultaneously inoculated into
urine, used as a culture medium.
Bacteriocins are generally stated as being either proteins or peptides, which
exhibit bactericidal effect on other closely related strains of bacteria. It appears,
however, that some bacteriocins are composed of a combination of various proteins
or are proteins with either lipid or saccharide components. Bacteriocins produced by
Gram-positive bacteria are most likely synthetized at first as prepeptides. Later a
leader peptide is separated from the rest of the prepeptide. This leader peptide then
exhibits biological activity. According to Anthony P. Pugsley (1984a, b) colicins
exhibit two main types of lethal effects. Some of them form channels in the
cytoplasmatic membrane, while others inhibit nuclease activity following their
entry into sensitive cells. However, in view of the small molecular mass of bacteriocins of Gram-positive bacteria it is assumed that they mostly affect the cellular
membranes.
Every kind of colicin is adsorbed onto a receptor molecule of the outer membrane. This phase of attack represents the first part of an interaction with sensitive
cells. It appears, though, that many bacteriocins of Gram-positive bacteria possess a
relatively small adsorption specificity. It is because the cellular wall of Grampositive bacteria allows passage of relatively large molecules that bacteriocin attack
against Gram-positive bacteria does not really require the need for a presence of
bacteriocin receptors as opposed to the outer membrane of Gram-negative cells.
Colicin production is always determined by plasmids. As stated earlier, the bestknown bacteriocins are colicins. They are produced by certain strains of Escherichia
coli and related species of the family Enterobacteriaceae. Immediately after contact
with colicin, the growth and multiplication of sensitive cells stop. Depending on the
general conditions and on the colicin type, in about 20 min the attacked rod-shaped
bacteria start to increase their volume and along with their loss of light refraction
they assume an ovoid or a spherical shape.
15.4.2 Characteristic Properties of Colicins
Colicins represent a group of antibiotic substances, which are characterized by
several common properties:
(a) All of them are either proteins or peptides.
(b) The structure of colicin molecules is coded by genes localized in special
plasmids, the so-called Col plasmids.
(c) Colicins are formed during growth of so-called colicinogenic cultures.
15 Microscopic World and the Phenomenon of Symbiosis in the Natural Environment
249