308
They exert an action similar to detergents on biological membranes. Surfactins
can vary based on the sequence of the seven amino acids and the length of the fatty
acid chain. These molecules are powerful biosurfactants used in biomedical and
pharmaceutical industry as antimicrobial, antimycoplasma and antiviral agents.
They are not antifungal in nature but show some synergetic action with iturin A
against fungus. Bacilysin is a small nonribosomal peptide secreted by B. subtilis.
This dipeptide consists of an L-alanyl (N-terminus) and L-anticapsin (C-terminus)
units linked by a peptide bond. It shows antimicrobial activity against a wide range
of bacteria including S. aureus and certain fungi, including Candida albicans.
Bacilysin binds and inhibits the enzyme glucosamine synthase that is required for
the synthesis of nucleotides, amino acids and coenzymes in microbial systems and
thereby bring about cell death. Chlorotetaine is a chlorinated derivative of bacilysin
with similar activity produced by certain strains of B. subtilis. Bacitracin (1486 Da)
is a mixture of related nonribosomal cyclic peptides secreted by certain strains of B.
licheniformis and B. subtilis. These peptides can disrupt the cell walls of both grampositive and gram-negative bacteria and are therefore used in topical applications as
an antimicrobial agent. Bacitracin is used together with polymixin and neomycin in
medicinal preparations to treat skin and eye infections. Polymixins are a group of
positively charged cyclic peptides isolated from cultures of Paenibacillus (Bacillus)
polymyxa strains and are used against gram-negative bacteria (Landman et al.
2008). The long fatty acid chains in the structure of polymixins show high affinity
to lipopolysaccharides of gram-negative cell membranes and hence have a disruptive effect on membrane integrity.
Polyketides In addition to peptides, the genus Bacillus also produces polyketides
with important biological activities. They are synthesized from acyl-CoA precursors by decarboxylative Claisen condensations. B. amyloliquefacians FZB42 and
GA1 strains produce difficidin (Fig. 12.6a), bacillaene (Fig. 12.6b) and macrolactin.
Difficidin, oxydifficidin and bacillaene are also isolated from fermentation broths of
B. subtilis strains. Difficidin and oxydifficidin are highly unsaturated 22-membered
macrolide phosphates with broad-spectrum antibacterial activity against both aerobic and anaerobic organisms. Difficidin was shown to be effective against Erwinia
amylovara, an important plant pathogen responsible for necrotrophic fire blight disease of apple and other members of rosaceous plants. Difficidin exerts its bactericidal activity by inhibiting protein synthesis.
Bacillaene (580 Da) is a bacteriostatic polyene antibiotic with a broad-spectrum
activity which acts by inhibiting protein synthesis. Macrolactins and their derivatives succinyl or glycosylated macrolactins are polyketides with a macrolide-like
structure containing three separated diene structure elements in a 24-membered lactone ring. At least 18 macrolactins were described from Bacillus spp., including
seven compounds with a molecular mass of 402 Da. They are shown to have antibacterial activity against gram-positive bacteria like S. aureus. Macrolactin A
(Fig. 12.6c) exhibits antiviral and cytotoxic activities. Macrolactin W, a recently
identified macrolactin, shows activity against both gram-positive and gram- negative
bacteria (Mondol et al. 2011).
D. Francis
They exert an action similar to detergents on biological membranes. Surfactins
can vary based on the sequence of the seven amino acids and the length of the fatty
acid chain. These molecules are powerful biosurfactants used in biomedical and
pharmaceutical industry as antimicrobial, antimycoplasma and antiviral agents.
They are not antifungal in nature but show some synergetic action with iturin A
against fungus. Bacilysin is a small nonribosomal peptide secreted by B. subtilis.
This dipeptide consists of an L-alanyl (N-terminus) and L-anticapsin (C-terminus)
units linked by a peptide bond. It shows antimicrobial activity against a wide range
of bacteria including S. aureus and certain fungi, including Candida albicans.
Bacilysin binds and inhibits the enzyme glucosamine synthase that is required for
the synthesis of nucleotides, amino acids and coenzymes in microbial systems and
thereby bring about cell death. Chlorotetaine is a chlorinated derivative of bacilysin
with similar activity produced by certain strains of B. subtilis. Bacitracin (1486 Da)
is a mixture of related nonribosomal cyclic peptides secreted by certain strains of B.
licheniformis and B. subtilis. These peptides can disrupt the cell walls of both grampositive and gram-negative bacteria and are therefore used in topical applications as
an antimicrobial agent. Bacitracin is used together with polymixin and neomycin in
medicinal preparations to treat skin and eye infections. Polymixins are a group of
positively charged cyclic peptides isolated from cultures of Paenibacillus (Bacillus)
polymyxa strains and are used against gram-negative bacteria (Landman et al.
2008). The long fatty acid chains in the structure of polymixins show high affinity
to lipopolysaccharides of gram-negative cell membranes and hence have a disruptive effect on membrane integrity.
Polyketides In addition to peptides, the genus Bacillus also produces polyketides
with important biological activities. They are synthesized from acyl-CoA precursors by decarboxylative Claisen condensations. B. amyloliquefacians FZB42 and
GA1 strains produce difficidin (Fig. 12.6a), bacillaene (Fig. 12.6b) and macrolactin.
Difficidin, oxydifficidin and bacillaene are also isolated from fermentation broths of
B. subtilis strains. Difficidin and oxydifficidin are highly unsaturated 22-membered
macrolide phosphates with broad-spectrum antibacterial activity against both aerobic and anaerobic organisms. Difficidin was shown to be effective against Erwinia
amylovara, an important plant pathogen responsible for necrotrophic fire blight disease of apple and other members of rosaceous plants. Difficidin exerts its bactericidal activity by inhibiting protein synthesis.
Bacillaene (580 Da) is a bacteriostatic polyene antibiotic with a broad-spectrum
activity which acts by inhibiting protein synthesis. Macrolactins and their derivatives succinyl or glycosylated macrolactins are polyketides with a macrolide-like
structure containing three separated diene structure elements in a 24-membered lactone ring. At least 18 macrolactins were described from Bacillus spp., including
seven compounds with a molecular mass of 402 Da. They are shown to have antibacterial activity against gram-positive bacteria like S. aureus. Macrolactin A
(Fig. 12.6c) exhibits antiviral and cytotoxic activities. Macrolactin W, a recently
identified macrolactin, shows activity against both gram-positive and gram- negative
bacteria (Mondol et al. 2011).
D. Francis