5. DISCUSSION Tremendous application potential exists in the field


Tremendous application potential exists in the field
of drug discovery from microbial sources. A number of novel secondary
metabolites and pigmented compounds with wide range of bioactivities against
several diseases have already been identified from microorgansims. Apart from
being colorants, microbial pigments have deeply penetrated into food, pharmaceutical
and cosmetic industries. They possess biological properties such as anticancer,
antimicrobial, antiproliferative and antioxidant activities (Rao et al., 2017). There are various fungal
and bacterial species isolated from soil, water and marine sources that produce
a wide range of pigments like, prodigiosin, carotenoids, melanine, pyocyanine
and violacein having various applications (Malik et al., 2012). In order to find a natural, alternative therapeutic
compound to treat cancer, the present work was aimed at evaluating   the
cytotoxic potential of bacterial pigments. In this pursuit, we isolated
pigmented bacteria from soil sources in Bangalore and were successful in collecting
five pigmented colonies. Two yellow coloured bacteria among the five have
demonstrated promising cytotoxicity to the cancer cell lines HeLa, HepG2 and
Jurkat. These two were identified as Pseudomonas
stutzeri JGI 52 and Micrococcus
terreus 19 by molecular methods.

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The pigments from these bacterial isolates were
extracted and their anticancer effects were analyzed on in-vitro cancer cell lines, HeLa, HepG2 and Jurkat. As the pigment
extracts from the current isolates have demonstrated promising anticancer
potential, they were partially purified using thin layer chromatography
technique to identify the compound which exhibited cytotoxicity. The yellow
pigment extract from P. stutzeri gave
a distinct visible yellow band with an Rf value of 0.73, which was named as
PY3. The yellow pigment extract from M. terreus
also had resulted in a visible yellow band with an Rf value of 0.64 and this band was named as MY3.
As these two yellow fractions, PY3 and MY3, demonstrated anti- proliferative
effects on all the in- vitro cancer
cell lines, they were chosen for further studies. To analyze the safety aspects
on humans, these fractions were checked on normal human peripheral lymphocytes
and also on a non cancerous cell line, CHO. 

The yellow
pigment PY3 excerted cytotoxic and antiproliferative effects on the cervical
cancer cell line HeLa, liver cancer cell line HepG2 and leukemia cell line
Jurkat. There
was a dose and time dependent growth inhibitory effect of PY3 on all the cancer
cells. PY3 markedly decreased the viability (less than 50%) of the cancer cells
analyzed, with an IC50 value of


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