181
novel compounds with diverse functions, including antitumor molecules (Gillespie
et al. 2002). Metagenomic libraries were effective in bringing forward pigments
with antibacterial potential like violacein, indigo, and cyclic peptides like nocardamine. Pederin, an antitumor agent, was initially known to be produced from the
beetle Paederus fuscipes. A metagenomic library developed using cosmid vectors
lead to the new fact that the gene encoding the molecule pederin was from an uncultured symbiotic bacteria Pseudomonad (Piel et al. 2004).
Metagenomics as a tool has helped to identify some of the marine microbes that
live in association with higher organisms, and these symbiotic microbes are responsible for the production of compounds that are of therapeutic value. Bryostatin,
dolastatins, didemnins, and ectenaiscidins are high clinical potential anticancer
compounds from marine organisms. Phylum porifera has treasured many highly
potential anticancer compounds like arabinosyl cytosine, halichondrin B, and spongistatin. Recent research has brought forward that most of these marine macroorganisms provide an optimum environment for growth of selected microbial
community. Metagenomic analysis has revealed that these microbial symbionts are
those which encode the genes for synthesis of so-called marine compounds from
higher organisms like sponge and porifera. The marine biochemical diversity is the
right field for employing metagenomic tools to hunt for natural products as most of
the marine microbial symbionts won’t grow in laboratory conditions.
Metagenomics has lead to the identification of novel antitumor polyketides from
microbial symbionts of sponges Theonella swinhoei, Pseudoceratina clavata, and
Discodermia dissolute (Ferrer et al. 2009). Scientific studies with help of metagenomic tools have brought up parts of the putative pederin, bryostatin, and onnamide
biosynthesis genes from clones of metagenomic libraries of a beetle, bryozoan, and
a sponge, respectively (Schirmer et al. 2005). The metagenomic library produced
from the marine sponge Didemnidae helped in the discovery of a new cytotoxic
cyclic peptide named patellamide. Study by Piel and others (2004) helped in isolating the gene clusters that code for production of pederin-related compounds
onnamide and psymberin from bacterial symbionts of Demospongiae sponges.
Later, Zimmermann and others (2009), studied the use of recombinant
O-methyltransferase, PedO, derived from pederin biosynthetic gene cluster to sitespecifically methylate mycalamide A giving the production of a derivative that
showed more potential anticancer activity.
7.5
Conclusions
Research in anticancer discovery will be a never waning field as the need for novel
drugs with specificity for targeted therapy is the need of modern era. Natural product research regained attention recently with the Nobel Prize in Physiology or
Medicine (2015), honoring researchers who discovered drugs from plant/microbes
that served the common man. Advanced methodologies and techniques have helped
in sequencing bacterial genomes that has opened the gates of diverse compounds
with novel structures and functional properties encoded within the basic four letters
7 Anti Cancer Agents from Microbes
novel compounds with diverse functions, including antitumor molecules (Gillespie
et al. 2002). Metagenomic libraries were effective in bringing forward pigments
with antibacterial potential like violacein, indigo, and cyclic peptides like nocardamine. Pederin, an antitumor agent, was initially known to be produced from the
beetle Paederus fuscipes. A metagenomic library developed using cosmid vectors
lead to the new fact that the gene encoding the molecule pederin was from an uncultured symbiotic bacteria Pseudomonad (Piel et al. 2004).
Metagenomics as a tool has helped to identify some of the marine microbes that
live in association with higher organisms, and these symbiotic microbes are responsible for the production of compounds that are of therapeutic value. Bryostatin,
dolastatins, didemnins, and ectenaiscidins are high clinical potential anticancer
compounds from marine organisms. Phylum porifera has treasured many highly
potential anticancer compounds like arabinosyl cytosine, halichondrin B, and spongistatin. Recent research has brought forward that most of these marine macroorganisms provide an optimum environment for growth of selected microbial
community. Metagenomic analysis has revealed that these microbial symbionts are
those which encode the genes for synthesis of so-called marine compounds from
higher organisms like sponge and porifera. The marine biochemical diversity is the
right field for employing metagenomic tools to hunt for natural products as most of
the marine microbial symbionts won’t grow in laboratory conditions.
Metagenomics has lead to the identification of novel antitumor polyketides from
microbial symbionts of sponges Theonella swinhoei, Pseudoceratina clavata, and
Discodermia dissolute (Ferrer et al. 2009). Scientific studies with help of metagenomic tools have brought up parts of the putative pederin, bryostatin, and onnamide
biosynthesis genes from clones of metagenomic libraries of a beetle, bryozoan, and
a sponge, respectively (Schirmer et al. 2005). The metagenomic library produced
from the marine sponge Didemnidae helped in the discovery of a new cytotoxic
cyclic peptide named patellamide. Study by Piel and others (2004) helped in isolating the gene clusters that code for production of pederin-related compounds
onnamide and psymberin from bacterial symbionts of Demospongiae sponges.
Later, Zimmermann and others (2009), studied the use of recombinant
O-methyltransferase, PedO, derived from pederin biosynthetic gene cluster to sitespecifically methylate mycalamide A giving the production of a derivative that
showed more potential anticancer activity.
7.5
Conclusions
Research in anticancer discovery will be a never waning field as the need for novel
drugs with specificity for targeted therapy is the need of modern era. Natural product research regained attention recently with the Nobel Prize in Physiology or
Medicine (2015), honoring researchers who discovered drugs from plant/microbes
that served the common man. Advanced methodologies and techniques have helped
in sequencing bacterial genomes that has opened the gates of diverse compounds
with novel structures and functional properties encoded within the basic four letters
7 Anti Cancer Agents from Microbes