339
of molluscs as source of antimicrobial compounds (Ramasamy and Murugan 2005).
Shell extracts of Donax faba and gut methanol extract of Perna viridis also exhibit
antibacterial activities (Giftson and Patterson 2014). Further studies down the road
are required for identification, isolation, and commercialization of bioactive molecules having antimicrobial activity from marine molluscs.
Arthropods have been speculated to produce antimicrobial molecules after the
observation of bactericidal activities of the plasma of lobster Homarus americanus
as early as 1972 (Stewart and Zwicker 1972). Crustacean species are known to produce antimicrobial peptides, e.g., penaeidins isolated from the hemolymph of the
shrimp Penaeus vannamei (Destoumieux et al. 1997). This molecule was shown to
have both antifungal and antibacterial activities following its large-scale production
employing recombinant DNA technologies. Penaeidins are found to be active
against filamentous fungi and Gram positive bacteria (Destoumieux et al. 1999).
Several extracts of crustaceans which showed antibacterial activity are being tested
for bioactive compounds that would aid in the development of new antibiotics
(Kiran et al. 2014).
Other invertebrates such as annelids are also found to produce antimicrobial substances. Organisms from all the three classes of phylum Annelida (Polychaeta,
Oligochaeta, and Hirudinea) are studied for their ability to produce antimicrobial
peptides (AMPs). Hedistin, perinerin, and arenicin are the main AMPs isolated
from different species of polycheates. The AMPs isolated from oligochaetes include
a peptide having 62 amino acids, lumbricin-1, its derivative lumbricin-1 (6-34) having 29 amino acids and 3 very short peptides, F-1, F-2, and OEP3121, having only
5 amino acids. Theromacin, theomyzin, and Perptide B are examples of AMPs islotated from organisms of class hirudinea (Tasiemski 2008).
13.7.3 Marine Extremophiles
The search for organisms that produce unique metabolites led researchers to explore
extreme habitats. The extreme conditions in the marine environment include high as
well as low temperatures, elevated hydrostatic pressure, and hypersalinity. Hypoxic
areas, oil-contaminated sites, and deep-sea sediments are also considered extreme
habitats. The main challenges of exploring these habitats are the extremely difficult
logistics procedure of collecting samples, unstable conditions at the sites for recollection of samples, and culturing the extremeophilic organisms in laboratory conditions. However, search for antimicrobials from deep-sea hydrothermal vents yielded
fruits in the form of antimicrobial peptide (AMP) alvinellacin from polychaetous
annelid Alvinella pompejana that inhabits active deep-sea hydrothermal vents
(Tasiemski et al. 2014) along with other bioactive compounds isolated from various
bacterial species (Branco et al. 2008). Though hypersaline environments are usually
highly alkaline and hypoxic they are inhabited by microorganisms including actinomycetes (Phillips et al. 2012; Swan et al. 2010; Tang et al. 2009; Ventosa 2006). A
recent finding that microorganisms of hypersaline microbial mat can produce antimicrobial and quorum sensing inhibitory compounds (Abed et al. 2013) points the
13 Novel Sources of Antimicrobials
of molluscs as source of antimicrobial compounds (Ramasamy and Murugan 2005).
Shell extracts of Donax faba and gut methanol extract of Perna viridis also exhibit
antibacterial activities (Giftson and Patterson 2014). Further studies down the road
are required for identification, isolation, and commercialization of bioactive molecules having antimicrobial activity from marine molluscs.
Arthropods have been speculated to produce antimicrobial molecules after the
observation of bactericidal activities of the plasma of lobster Homarus americanus
as early as 1972 (Stewart and Zwicker 1972). Crustacean species are known to produce antimicrobial peptides, e.g., penaeidins isolated from the hemolymph of the
shrimp Penaeus vannamei (Destoumieux et al. 1997). This molecule was shown to
have both antifungal and antibacterial activities following its large-scale production
employing recombinant DNA technologies. Penaeidins are found to be active
against filamentous fungi and Gram positive bacteria (Destoumieux et al. 1999).
Several extracts of crustaceans which showed antibacterial activity are being tested
for bioactive compounds that would aid in the development of new antibiotics
(Kiran et al. 2014).
Other invertebrates such as annelids are also found to produce antimicrobial substances. Organisms from all the three classes of phylum Annelida (Polychaeta,
Oligochaeta, and Hirudinea) are studied for their ability to produce antimicrobial
peptides (AMPs). Hedistin, perinerin, and arenicin are the main AMPs isolated
from different species of polycheates. The AMPs isolated from oligochaetes include
a peptide having 62 amino acids, lumbricin-1, its derivative lumbricin-1 (6-34) having 29 amino acids and 3 very short peptides, F-1, F-2, and OEP3121, having only
5 amino acids. Theromacin, theomyzin, and Perptide B are examples of AMPs islotated from organisms of class hirudinea (Tasiemski 2008).
13.7.3 Marine Extremophiles
The search for organisms that produce unique metabolites led researchers to explore
extreme habitats. The extreme conditions in the marine environment include high as
well as low temperatures, elevated hydrostatic pressure, and hypersalinity. Hypoxic
areas, oil-contaminated sites, and deep-sea sediments are also considered extreme
habitats. The main challenges of exploring these habitats are the extremely difficult
logistics procedure of collecting samples, unstable conditions at the sites for recollection of samples, and culturing the extremeophilic organisms in laboratory conditions. However, search for antimicrobials from deep-sea hydrothermal vents yielded
fruits in the form of antimicrobial peptide (AMP) alvinellacin from polychaetous
annelid Alvinella pompejana that inhabits active deep-sea hydrothermal vents
(Tasiemski et al. 2014) along with other bioactive compounds isolated from various
bacterial species (Branco et al. 2008). Though hypersaline environments are usually
highly alkaline and hypoxic they are inhabited by microorganisms including actinomycetes (Phillips et al. 2012; Swan et al. 2010; Tang et al. 2009; Ventosa 2006). A
recent finding that microorganisms of hypersaline microbial mat can produce antimicrobial and quorum sensing inhibitory compounds (Abed et al. 2013) points the
13 Novel Sources of Antimicrobials