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Title: A molecular investigation of sodium channel blocking toxin production by marine bacteria
Author: Johnston, M. P.
Awarding Body: University of Aberdeen
Current Institution: University of Aberdeen
Date of Award: 2005
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The first step of this work was to determine if seven SCB toxin-producing bacteria and five TTX producers bore plasmids that encoded for toxin production. Only one of the twelve strains was found to have a plasmid and curing it was not possible.  It was therefore concluded that, in all likelihood, in the majority of strains tested, toxin-producing genes were located on the chromosome. Although several different classes of signal molecules have been identified to date, most research efforts have concentrated on the N-acyl homoserine lactones (AHLs). The twelve SCB toxin- and TTX producers were tested for AHLs using a suite of biosensors. The bioassays indicated that over half of the strains produced signal molecules, but this was not enough to draw a conclusive correlation between AHLs and toxin production. Surprisingly, bacterium 667-2 (Roseobacter clade) was shown to produce up to six different AHLs. Using Electrospray Ionisation Mass Spectrometry (ESI MS/MS), it was revealed that 667-2 constitutively produces N-(3-hydroxydecanoyl)-L-homoserine lactone, an AHL reported only once before, and hexandecanoyl homoserine lactone, a novel AHL. It was not possible to determine what phenotypes these AHLs regulate, but given the growing interest in Roseobacter, work on this strain may continue. Several groups have reported successful mutagenesis of marine bacteria employing mini-Tn5 vectors. Like other researchers, this work found that antibiotic resistance and DNase production by SCB toxin- and TTX producers limited the scope for selection of genuine mutants. However, diparental filter mating using potassium tellurite to select against the donor and chloramphenicol against the marine recipients was confirmed as successful. The next step in this work would have been to identify non-toxic mutants and sequence their genes in order to elucidate the biosynthetic pathway for toxin production.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available