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components of the outer membrane that play a role in cell viability and pathogenesis. LspA offers a novel target for antibiotics. Myxovirescins (Fig. 12.8f) represent
a class of LspA binding antibiotics isolated from myxobacterial strains. The first
antibiotic of this type was isolated from Myxococcus virescens strain Mx v48. The
basic structure contains a 28-member ring with lactam and lactone functionality.
Myxovirescins are active against gram-negative bacteria like E. coli and P. aerugenosa and gram-positive bacteria like S. aureus and B. megaterium. Myxovirescins
bind to the type II signal LspA to bring about its bactericidal effect. Binding to LspA
results in a toxic accumulation of lipopolysaccharides inside the cells, leading to a
lethal cross-linking of the cell wall and the inner membrane and results in the
improper localization of lipoproteins on the outer membrane.
12.4.5.7 Other Antibiotics
Myxobacteria produce a number of antimicrobials of which the mode of action is
not yet determined. Chondrochlorens are produced by Chondromyces crocatus
strain Cmc5. They are chlorohydroxy styryl amides with the styrene moiety linked
with an aliphatic side chain by an amide bond. Chondrochlorens A and B are
described. Chondrochlorens A shows weak inhibitory activity against Micrococcus
luteus and Schizosaccharomyces bombe. Chondrochlorens B is active against M.
luteus and B. subtilis (Jansen et al. 2003). Indiacens A and B are 3-formylindol
derivatives isolated from Sandaracinus amylolyticus strain NOSO-4 T, belonging to
a recently characterized myxobacterial genus. Indiacin B is the chlorinated derivative of Indiacin A. The compound shows moderate activity against gram-positive
and gram-negative bacteria (Steinmetz et al. 2012).
Maracin A and maracen A are molecules with antimycobacterial activity isolated
from Sorangium cellulosum strain Soce 880 and Soce 1128, respectively. Maracin
A is characterized by the presence of an unusual ethynyl-trans-vinyl ether moiety
which is replaced by an α-chlorovinyl group in maracen A. Nannochelins are a
group of citrate hydroxamate siderophores isolated from Nannocystis exedens strain
Na e485. Nannochelins show antibacterial activity against gram-positive organisms, including Bacillus spp. and Brevibacterium ammoniagenes along with weak
antifungal activity. Roimatacene is a chemically unstable polyenic carboxylic acid
isolated from Cystobacter ferrugineus Cb G35. The molecule shows selective activity against gram-negative bacteria unlike other antibiotics derived from myxobacteria (Zander et al. 2011). Sorangiadenosine isolated from Sorangium cellulosum
strain KM1003 contains a nucleoside substituted with a sesquiterpene. It is a moderate inhibitor of gram-positive bacteria (Ahn et al. 2008). Sulfangolids are sulfate
ester containing secondary metabolites isolated from S. cellulosum strains. They are
structurally composed of macrolides conjugated to a triene or tetraene (Zander et al.
2012). Kulkenon is another metabolite structurally identical to sulfangolids isolated
from S. cellulosum (Symkenberg and Kalesse 2014). Salimyxin B and enhygrolide
A were isolated from the marine myxobacterium Enhygromyxa salina, and they
show antimicrobial activity against Arthrobacter cristallopoietes (Felder et al.
2013).
D. Francis
components of the outer membrane that play a role in cell viability and pathogenesis. LspA offers a novel target for antibiotics. Myxovirescins (Fig. 12.8f) represent
a class of LspA binding antibiotics isolated from myxobacterial strains. The first
antibiotic of this type was isolated from Myxococcus virescens strain Mx v48. The
basic structure contains a 28-member ring with lactam and lactone functionality.
Myxovirescins are active against gram-negative bacteria like E. coli and P. aerugenosa and gram-positive bacteria like S. aureus and B. megaterium. Myxovirescins
bind to the type II signal LspA to bring about its bactericidal effect. Binding to LspA
results in a toxic accumulation of lipopolysaccharides inside the cells, leading to a
lethal cross-linking of the cell wall and the inner membrane and results in the
improper localization of lipoproteins on the outer membrane.
12.4.5.7 Other Antibiotics
Myxobacteria produce a number of antimicrobials of which the mode of action is
not yet determined. Chondrochlorens are produced by Chondromyces crocatus
strain Cmc5. They are chlorohydroxy styryl amides with the styrene moiety linked
with an aliphatic side chain by an amide bond. Chondrochlorens A and B are
described. Chondrochlorens A shows weak inhibitory activity against Micrococcus
luteus and Schizosaccharomyces bombe. Chondrochlorens B is active against M.
luteus and B. subtilis (Jansen et al. 2003). Indiacens A and B are 3-formylindol
derivatives isolated from Sandaracinus amylolyticus strain NOSO-4 T, belonging to
a recently characterized myxobacterial genus. Indiacin B is the chlorinated derivative of Indiacin A. The compound shows moderate activity against gram-positive
and gram-negative bacteria (Steinmetz et al. 2012).
Maracin A and maracen A are molecules with antimycobacterial activity isolated
from Sorangium cellulosum strain Soce 880 and Soce 1128, respectively. Maracin
A is characterized by the presence of an unusual ethynyl-trans-vinyl ether moiety
which is replaced by an α-chlorovinyl group in maracen A. Nannochelins are a
group of citrate hydroxamate siderophores isolated from Nannocystis exedens strain
Na e485. Nannochelins show antibacterial activity against gram-positive organisms, including Bacillus spp. and Brevibacterium ammoniagenes along with weak
antifungal activity. Roimatacene is a chemically unstable polyenic carboxylic acid
isolated from Cystobacter ferrugineus Cb G35. The molecule shows selective activity against gram-negative bacteria unlike other antibiotics derived from myxobacteria (Zander et al. 2011). Sorangiadenosine isolated from Sorangium cellulosum
strain KM1003 contains a nucleoside substituted with a sesquiterpene. It is a moderate inhibitor of gram-positive bacteria (Ahn et al. 2008). Sulfangolids are sulfate
ester containing secondary metabolites isolated from S. cellulosum strains. They are
structurally composed of macrolides conjugated to a triene or tetraene (Zander et al.
2012). Kulkenon is another metabolite structurally identical to sulfangolids isolated
from S. cellulosum (Symkenberg and Kalesse 2014). Salimyxin B and enhygrolide
A were isolated from the marine myxobacterium Enhygromyxa salina, and they
show antimicrobial activity against Arthrobacter cristallopoietes (Felder et al.
2013).
D. Francis