Coumarin: a novel player in microbial quorum sensing and biofilm formation inhibition

Antibiotic resistance is a growing threat worldwide, causing serious problems in the treatment of microbial infections. The discovery and development of new drugs is urgently needed to overcome this problem which has greatly undermined the clinical effectiveness of conventional antibiotics. An intricate cell-cell communication system termed quorum sensing (QS) and the coordinated multicellular behaviour of biofilm formation have both been identified as promising targets for the treatment and clinical management of microbial infections. QS systems allow bacteria to adapt rapidly to harsh conditions, and are known to promote the formation of antibiotic tolerant biofilm communities. It is well known that biofilm is a recalcitrant mode of growth and it also increases bacterial resistance to conventional antibiotics. The pharmacological properties of coumarins have been well described, and these have included several that possess antimicrobial properties. More recently, reports have highlighted the potential role of coumarins as alternative therapeutic strategies based on their ability to block the QS signalling systems and to inhibit the formation of biofilms in clinically relevant pathogens. In addition to human infections, coumarins have also been found to be effective in controlling plant pathogens, infections in aquaculture, food spoilage and in reducing biofouling caused by eukaryotic organisms. Thus, the coumarin class of small molecule natural product are emerging as a promising strategy to combat bacterial infections in the new era of antimicrobial resistance

Rapid phosphorylation of MAP kinase-like proteins in two species of Arctic kelps in response to temperature and UV radiation stress

Mitogen-Activated Protein Kinases (MAPKs) are a group of cytoplasmic phosphoproteins that constitute the central core of the signalling network to respond to stress in most organisms. Their role in stress responses has been extensively studied in organisms from yeast to humans, and recently, their presence has also been described in higher plants as well as in micro- and macroalgae. In this study, we demonstrate via short experiments (1 h in duration), the rapid activation of two MAPKs similar to p38 and JNK of mammalian cells, in the Arctic kelps Laminaria solidungula and Saccharina latissima exposed to temperature and UV stress. The molecular mass of p38 is 40 KDa in L. solidungula and 42 KDa in S. latissima, while two JNKs were detected in both species, of 36 and 42 KDa in L. solidungula, and 36 and 40 KDa in S. latissima. These MAPKs are highly phosphorylated in response to temperature and UV light. In S. latissima, both p38 and the JNK showed higher phosphorylation at 2C than at 7C, while the reverse response was shown for L. solidungula. In addition, a significant increase in phosphorylation of both kinases was found following exposure to UV radiation (UVR). Exposure to PAR+UVA+UVB induced higher phosphorylation than PAR+UVA in L. solidungula, especially at 7C. In S. latissima, this response occurred only with JNK, and no differences in p38 phosphorylation between PAR+UVA and PAR+UVA+UVB at any temperature were observed. These results indicate the possible participation of MAPK-like proteins in response to stress in Arctic kelps, and that their activation is species-specific