334
organism. They exhibit broad spectrum (Gram positive bacteria, Gram negative
bacteria, fungi, and virus) antimicrobial activities (Saeed et al. 2013). Pleurocidin,
lactoferrin, defensins, and protamine are some of the AMPs with potential antimicrobial properties. Most of the AMPs rapidly kill microbes by targeting their membranes and reduce the possibility of mutation and eventual drug resistance (Tiwari
et al. 2009). These antimicrobial peptides are isolated from various sources such as
mucous membranes of fish (pleurocidin) (Cole et al. 2000), epithelial cells of
chicken and turkeys (defensins) (Tiwari et al. 2009), and milk (lactoperoxidase)
(Seifu et al. 2005). In addition to peptides, certain polysaccharides and lipids of
animal origin are also reported to have broad spectrum antimicrobial properties.
They are found to be active against Gram positive and Gram negative bacteria and
fungi. Chitosan – a natural polysaccharide obtained from the exoskeletons of certain
arthropods – and milk lipids are examples of such molecules (Saeed et al. 2013).
13.6 Extreme Habitats
As the name implies, extremophiles live in extreme habitats and require unusual
mechanisms to adapt to such conditions and they produce diverse molecules in their
body in order to aid them in the process (Sanchez et al. 2009). Resources untapped
thus far were explored for identification of natural compounds that could possess
antimicrobial activities (Zengler et al. 2005). Microorganisms living in extreme
habitats produce unique molecules that help them adapt to the unusual life conditions. Therapeutic potential of many such compounds have been identified (Sanchez
et al. 2009). Extremophilic microorganisms were recognized to be promising
sources of therapeutically important compounds after the identification of antimicrobial activities of such molecules (Ravot et al. 2006). Exploration did not leave
extreme habitats such as caves, as cave biofilms were relatively unstudied ecosystems (Boston et al. 2001). These were later found to be excellent sources of new
antimicrobial compounds (Maria de Lurdes and Dapkevicius 2013). Last two
decades witnessed discovery of a number of new species from gold mines and caves
from different parts of the world that produce useful secondary metabolites (Cheng
et al. 2013; Kay et al. 2013; Lee 2006, Margesin et al. 2004; Maria de Lurdes and
Dapkevicius 2013; Rule and Cheeptham 2013). Various molecular and cultureindependent methods are being employed to identify organisms from volcanic caves
and lava tubes (Rule and Cheeptham 2013). Such studies are the need of the hour as
they are directed toward identification and characterization of novel compounds and
qualify them to be used in clinical space.
Hot springs, sulfurous thermal springs, stromatolytes, etc. are examples of terrestrial extreme habitats. Recent studies show that extremophilic microbes are
another probable source of novel biomolecules due to their adaptive ability to
unusual habitats. Early in this century a compound called pyochelin was isolated
from extracts of a novel thermophilic species of Pseudomonas, which was found to
have antifungal activity (Combie et al. 2001). Later, investigations were successful
in finding microcin-like compounds (proteinaceous toxins produced by bacteria to
Lini Nirmala and D.P. Zyju
organism. They exhibit broad spectrum (Gram positive bacteria, Gram negative
bacteria, fungi, and virus) antimicrobial activities (Saeed et al. 2013). Pleurocidin,
lactoferrin, defensins, and protamine are some of the AMPs with potential antimicrobial properties. Most of the AMPs rapidly kill microbes by targeting their membranes and reduce the possibility of mutation and eventual drug resistance (Tiwari
et al. 2009). These antimicrobial peptides are isolated from various sources such as
mucous membranes of fish (pleurocidin) (Cole et al. 2000), epithelial cells of
chicken and turkeys (defensins) (Tiwari et al. 2009), and milk (lactoperoxidase)
(Seifu et al. 2005). In addition to peptides, certain polysaccharides and lipids of
animal origin are also reported to have broad spectrum antimicrobial properties.
They are found to be active against Gram positive and Gram negative bacteria and
fungi. Chitosan – a natural polysaccharide obtained from the exoskeletons of certain
arthropods – and milk lipids are examples of such molecules (Saeed et al. 2013).
13.6 Extreme Habitats
As the name implies, extremophiles live in extreme habitats and require unusual
mechanisms to adapt to such conditions and they produce diverse molecules in their
body in order to aid them in the process (Sanchez et al. 2009). Resources untapped
thus far were explored for identification of natural compounds that could possess
antimicrobial activities (Zengler et al. 2005). Microorganisms living in extreme
habitats produce unique molecules that help them adapt to the unusual life conditions. Therapeutic potential of many such compounds have been identified (Sanchez
et al. 2009). Extremophilic microorganisms were recognized to be promising
sources of therapeutically important compounds after the identification of antimicrobial activities of such molecules (Ravot et al. 2006). Exploration did not leave
extreme habitats such as caves, as cave biofilms were relatively unstudied ecosystems (Boston et al. 2001). These were later found to be excellent sources of new
antimicrobial compounds (Maria de Lurdes and Dapkevicius 2013). Last two
decades witnessed discovery of a number of new species from gold mines and caves
from different parts of the world that produce useful secondary metabolites (Cheng
et al. 2013; Kay et al. 2013; Lee 2006, Margesin et al. 2004; Maria de Lurdes and
Dapkevicius 2013; Rule and Cheeptham 2013). Various molecular and cultureindependent methods are being employed to identify organisms from volcanic caves
and lava tubes (Rule and Cheeptham 2013). Such studies are the need of the hour as
they are directed toward identification and characterization of novel compounds and
qualify them to be used in clinical space.
Hot springs, sulfurous thermal springs, stromatolytes, etc. are examples of terrestrial extreme habitats. Recent studies show that extremophilic microbes are
another probable source of novel biomolecules due to their adaptive ability to
unusual habitats. Early in this century a compound called pyochelin was isolated
from extracts of a novel thermophilic species of Pseudomonas, which was found to
have antifungal activity (Combie et al. 2001). Later, investigations were successful
in finding microcin-like compounds (proteinaceous toxins produced by bacteria to
Lini Nirmala and D.P. Zyju