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Quorum sensing in the cyanobacterium Gloeothece PCC 6909. / Dilara Islam Sharif
Swansea University Author: Dilara Islam Sharif
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The thesis sought to study whether cyanobacteria utilise the process of quorum sensing during their growth, to identify any quorum sensing molecules produced by the cyanobacteria Gloeothece PCC 6909/1 and to study the effect of any such molecules in aexenic cultures of the organism. The study presen...
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The thesis sought to study whether cyanobacteria utilise the process of quorum sensing during their growth, to identify any quorum sensing molecules produced by the cyanobacteria Gloeothece PCC 6909/1 and to study the effect of any such molecules in aexenic cultures of the organism. The study presents the first evidence of N-octanoyl homoserine lactone (C8-HSL) quorum sensing molecule from axenic cultures of the cyanobacterium PCC 6909 and its sheathless mutant PCC 6909/1 and that the production of this molecule followed a density dependent accumulation, a common feature of many quorum sensing systems. The response of the Gloeothece proteome to exogenous concentrations of C8-HSL was examined, indicating changes in 43 protein spots on a 2D-PAGE gel, thereby indicating a response through global changes in protein expression. Among the 15 proteins that showed more than 2 fold expression changes, RuBisCo, glutamate synthase, chorismate synthase, a LysR family of transcriptional regulator (all up regulated) enolase and aldolase (down regulated) could be identified. A number of phosphorylated proteins also showed increased accumulation suggesting changes in the phosphoproteome of Gloeothece. A response to C8-HSL was also detected in physiological changes of the organism through decreased accumulation of extracellular soluble carbohydrates and an increased acid phosphatase activity from cell extracts. In conclusion, this study presents evidence that the cyanobacterium Gloeothece employs a C8-HSL based quorum sensing system through the accumulation and response to a C8-HSL signal. These findings can help increase our understanding of how colonial cyanobacteria encounter stress at high cell densities.
Faculty of Science and Engineering