Abstract
Several gram-negative bacterial species use N-acyl homoserine lactone (AHL) molecules as quorum sensing (QS) signals to regulate various biological functions. Similarly various bacteria can stimulate, inhibit or inactivate quorum sensing signals in other bacteria by producing molecules called quorum sensing inhibitors (QSI). In the present study, QSI screenings were conducted on several halophilic and halotolerant bacteria isolated from marine environments and saltpans, using Serratia rubidaea N-1 as an indicator organism. S. rubidaea controls the production of red pigment, prodigiosin by acyl homoserine lactone quorum sensing. We have found that S. rubidaea N-1 produces high amount of pigment when growth medium contains 0.5 to 1 M NaCl and hence we decided this strain as a suitable indicator for finding QSI. Among several bacteria which were isolated from salt pans of South India, 5 strains showed sufficient growth in the wide concentrations of NaCl, 0.5 to 3 M. Results showed that some marine bacteria have the ability to produce QSI which was observed by the lack of pigmentation of S. rubidaea N-1 in the vicinity of the test sample. This simple screening strategy using the pigment inhibition of S. rubidaea N-1 strain allows the rapid and sensitive detection of potential QS blockers from large number of bacteria from marine environments.
