intestinal tract [14]. Lactobacilli are also potentially useful as carriers for oral
immunization, since orally administered lactobacilli trigger both a mucosal and
systemic immune reaction against epitopes associated with these organisms
[15, 16].
1.2
Bacteriocins
Bacteriocins are proteinaceous compounds produced by bacteria, both Grampositive and Gram-negative, and they are active chiefly against closely related
bacteria [17]. The discovery of bacteriocins dates back to 1925, when E. coli V
was shown to produce an antimicrobial compound active against E. coli F [18].
These antimicrobial substances by E. coli were named colicins and 17 different
types, based on their adsorption, were later reported [19]. Like the colicins
(25–90 kDa, produced by E. coli and active against other Enterobacteriaceae)
and microcins (<10 kDa, produced by Enterobacteriaceae and active against
other Gram-negative bacteria), the bacteriocins produced by Gram-positive
bacteria were defined as proteinaceous compounds that kill only closely related
species [17, 20]. Although true for the majority of compounds, it is now evident
that bacteriocins produced by lactic acid bacteria display bactericidal activity
beyond species that are closely related [21]. Except for the colicins and the
microcins, many other bacteriocins produced by non-lactic acid bacteria such
as Bacillus, Staphylococcus, Streptomyces, Streptoverticillium, etc. have been
reported [1, 22, 23].
The first report of the production of a bacteriocin produced by lactic acid
bacteria was made in 1928 [24]. The substance was determined as a polypeptide
[25] and subsequently named nisin [26, 27]. Since that time the bacteriocin field
has expanded exponentially, and now bacteriocins produced by all genera of the
lactic acid bacteria have been reported [1, 21].
The majority of bacteriocins from lactic acid bacteria have been characterized according to the early definition of a proteinaceous inhibitor, estimation
of their molecular mass, and determination of their inhibition spectrum [1, 21].
Recent developments in the biochemical and molecular biological characterization of many of these compounds have elucidated their genetic organization, structures and mode of action. Despite their heterogeneity, bacteriocins
produced by lactic acid bacteria were subdivided into three distinct classes
based on these genetic and biochemical resemblances [28].
1.2.1
Lantibiotics (Class I)
Lantibiotics are small, membrane-active peptides (<5 kDa) containing the
unusual amino acids lanthionine, b-methyl-lanthionine, and the dehydrated
residues dehydroalanine and dehydrobutyrine; e.g. nisin, lacticin 481, carnocin
U-149, lactocin S, sublancin 168 [29–38]. The intrachain positioning of these
polycyclic structures of the lantibiotics has been used to group them into linear
(Group IA) or circular (Group IB) lantibiotics [39]. Based on similarities in the
Antimicrobial Peptides of Lactic Acid Bacteria: Mode of Action, Genetics and Biosynthesis
23
immunization, since orally administered lactobacilli trigger both a mucosal and
systemic immune reaction against epitopes associated with these organisms
[15, 16].
1.2
Bacteriocins
Bacteriocins are proteinaceous compounds produced by bacteria, both Grampositive and Gram-negative, and they are active chiefly against closely related
bacteria [17]. The discovery of bacteriocins dates back to 1925, when E. coli V
was shown to produce an antimicrobial compound active against E. coli F [18].
These antimicrobial substances by E. coli were named colicins and 17 different
types, based on their adsorption, were later reported [19]. Like the colicins
(25–90 kDa, produced by E. coli and active against other Enterobacteriaceae)
and microcins (<10 kDa, produced by Enterobacteriaceae and active against
other Gram-negative bacteria), the bacteriocins produced by Gram-positive
bacteria were defined as proteinaceous compounds that kill only closely related
species [17, 20]. Although true for the majority of compounds, it is now evident
that bacteriocins produced by lactic acid bacteria display bactericidal activity
beyond species that are closely related [21]. Except for the colicins and the
microcins, many other bacteriocins produced by non-lactic acid bacteria such
as Bacillus, Staphylococcus, Streptomyces, Streptoverticillium, etc. have been
reported [1, 22, 23].
The first report of the production of a bacteriocin produced by lactic acid
bacteria was made in 1928 [24]. The substance was determined as a polypeptide
[25] and subsequently named nisin [26, 27]. Since that time the bacteriocin field
has expanded exponentially, and now bacteriocins produced by all genera of the
lactic acid bacteria have been reported [1, 21].
The majority of bacteriocins from lactic acid bacteria have been characterized according to the early definition of a proteinaceous inhibitor, estimation
of their molecular mass, and determination of their inhibition spectrum [1, 21].
Recent developments in the biochemical and molecular biological characterization of many of these compounds have elucidated their genetic organization, structures and mode of action. Despite their heterogeneity, bacteriocins
produced by lactic acid bacteria were subdivided into three distinct classes
based on these genetic and biochemical resemblances [28].
1.2.1
Lantibiotics (Class I)
Lantibiotics are small, membrane-active peptides (<5 kDa) containing the
unusual amino acids lanthionine, b-methyl-lanthionine, and the dehydrated
residues dehydroalanine and dehydrobutyrine; e.g. nisin, lacticin 481, carnocin
U-149, lactocin S, sublancin 168 [29–38]. The intrachain positioning of these
polycyclic structures of the lantibiotics has been used to group them into linear
(Group IA) or circular (Group IB) lantibiotics [39]. Based on similarities in the
Antimicrobial Peptides of Lactic Acid Bacteria: Mode of Action, Genetics and Biosynthesis
23