ISOLATION AND IDENTIFICATION OF PIGMENT PRODUCING BACTERIA FROM THE RATARGUL SWAMP FOREST SOIL

Abstract

Pigments are one of the most significant secondary metabolites produced by
microorganisms. The aim of the present study was to isolate and identify pigmentproducing
bacteria from the Ratargul Swamp Forest (RSF) soil, which is the one and only
fresh water swamp forest of Bangladesh. Soil samples were randomly collected from 10
different quadrates (10 m x 10 m) of RSF. The pH values of the soil samples were found
to be strongly acidic and ranged between 4.71 and 5.48. Bacterial load of the samples
ranged from 1.33×105 to 1.93×108 cfu/g, 6.05×106 to 9.07×107 cfu/g and from 1.16×107 to
1.61×108 cfu/g on nutrient agar (NA), peptone yeast-extract glucose (PYG) agar and
Luria-Bertani (LB) agar media, respectively. Interestingly, both the highest and lowest
bacterial counts were observed on NA, which was 1.93×108 cfu/g and 1.33×105 cfu/g,
respectively. The isolates were found to produce various pigments like yellow, red, dark
orange and sweet pink during their colony developments. A total of 71 bacterial isolates
were obtained of which 11 were subjected to further study. All the selected bacteria were
found to be rod shaped. Out of the 11 isolates, 9 were Gram-positive and 2 were Gramnegative.
Provisionally identified potential pigment producing eight bacterial isolates
were identified by using molecular marker. Seven of them were matched with their
conventional identification up to generic level but conventionally identified Erwinia
stewartii was found to be as Aeromonas sobria. Among the 11 isolates, 8 could produce
three different types of pigments namely red, yellow and dark orange during in vitro
pigment production. The isolated pigment producing bacteria could be used for better
biotechnological application.