Marine antibiotic

From a microbe found in the Sunderbans

 
Published: Saturday 04 July 2015

Fish to microbes: Sunderbans y (Credit: Pradip saha / CSE)font class='UCASE'>indian researchers have identified a marine microbe that shows antimicrobial activity against bacteria, including several that are multiple-drug resistant (mdr) such as Staphylococcus aureus (which causes skin and blood infections), molds and yeast in lab experiments. The newly detected microorganism thrives in the marine environment of Lothian island in the Sunderbans.

The scientists from Kolkata's Jadavpur University, Indian Institute of Chemical Biology, Peerless Hospital and B K Roy Research Centre have isolated the active antimicrobial compound, which is a lipid. "The active compound shows very strong activity against bacteria and fungi," says Jaydeep Mukherjee, who headed the research team. "The active compound is a potential target for drug design," he claims.

The microbe belongs to Actinobacteria, a group of gram-positive bacteria that live in soil. "We christened it as Actinobacterium ms 3/20," says Mukherjee. The researchers found that seawater stimulates the microbe to churn out the active compound. The findings of the study were published in the February issue of Applied Microbiology and Biotechnology (Vol 66, No 5).

In recent years, new avatars of mdr bacteria have posed a serious threat to human health. Driven by the need to develop new antimicrobial agents, the team from Kolkata turned its attention to Sunderbans, whose microbial diversity remains largely unexplored. They found A ms 3/20 in the sediment of Lothian island and isolated it in a medium comprising a host of chemical ingredients such as starch, distilled and natural seawater. When grown for 96 hours in a medium comprising distilled water, starch, glucose, sodium chloride and other chemicals, it produced an active antimicrobial compound. "A deep yellow pellet-like structure signals the antimicrobial compound production phase," says Mukherjee.

The microorganism, together with its active antimicrobial compound, was found to inhibit the growth of disease-causing microbes including S aureus (strain 23602) that is resistant to drugs such as ciprofloxacin, cefataxamine, cotrimoxazole and methicillin; Escherichia coli (strain dh5a) and fungi Aspergillus niger (strain mtcc1344). In a separate experiment, the Kolkata scientists exposed the pathogenic bacteria and fungi only to the purified active compound and found evidence of antibacterial and antifungal activities similar to those exhibited by the microorganism.

The researchers also studied the effects of various growth medium ingredients on the production of the antimicrobial compound. "It has been found that glucose produced a slightly higher antimicrobial activity," Mukherjee said, as did the presence of 40-60 per cent seawater in distilled water. Increase in oxygen concentration of the growth medium revved up the synthesis of antimicrobial compound, indicating the microorganism prefers an oxygen-rich environment, concludes Mukherjee.

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