Extracellular polysaccharides of a copper-sensitive and a copper-resistant Pseudomonas aeruginosa strain:: synthesis, chemical nature and copper binding

Extracellular polysaccharides (EPS) of a copper-sensitive (Cu-s) and a copper-resistant (Cu-r) Pseudomonas aeruginosa strain were investigated in terms of their production, chemical nature and response towards copper exposure. The extent of EPS synthesis by the resistant strain (4.78 mg mg(-1) cell dry wt.) was considerably higher over its sensitive counterpart (2.78 mg mg(-1) dry wt.). FTIR-spectroscopy and gas chromatography revealed that both the polymers were acidic in nature, containing alginate as the major component along with various neutral- and amino-sugars. Acid content in the Cu-r EPS (480.54 mg g(-1)) was greater than that in the Cu-s EPS (442.0 mg g(-1)). Presence of Cu2+ in the growth medium caused a dramatic stimulation (approximately 4-fold) in EPS synthesis by the Cu-r strain, while in a similar condition, the Cu-s failed to exhibit such response. The polymer of the resistant strain showed elevated Cu2+ binding (320 mg g(-1) EPS) compared to that of the sensitive type (270 mg g(-1)). The overall observations show the potential of the Cu-r EPS for its deployment in metal bioremediation.