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Title: Interactions between sponges and marine bacteria as a route to the discovery of novel bioactive compounds
Author: Ismail, Noraznawati
ISNI:       0000 0001 3587 438X
Awarding Body: Heriot-Watt University
Current Institution: Heriot-Watt University
Date of Award: 2006
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The bacterial community architecture associated with four species of sponges, Halichondria panicea, Suberites domuncula, S. carnosus and Pachymatismajohnstonia 'was investigated using culture-dependent and culture-independent strategies. Marine '/ agar was found to be the best of several media used for cultivation of culturable bacteria : associated with sponges. Molecular methods, including denaturing gradient gel ,electrophoresis (DGGE), 16S rDNA cloning and sequence analysis suggested a : bacterial community different from that identified using culture-dependent methods. DGGE can provide a profile of the whole community of the sponge and facilitate screening of large-scale samples. 90% ofthe bacteria associated with these four sponges were sponge species-specific. S. carnosus was also transferred to an aquarium to study kinetic changes of sponge-associ~tedbacterial communities. DGGE analysis showed 'the consistent presence of some particular bands suggesting the continued presence of species of symbiotic bacteria. Four Bacillus species (B. licheniformis SC-43, B. subtilis SD-8, B. pumilus HP-48 and B. cereus HP-22) isolated from the sponges exhibited antagonistic activity against isolates of Gram-positive bacteria obtained from the same .sponges. All strains tested were active against Micrococcus luteus, strain HP-5!6 isolated from H. panicea. This suggests that HP-5!6 can be used in the laboratory as a sensitive indicator of activity. A comparison of several media found Nutrient Agar! Broth containing glycerol and iron (NGF) to be the best medium tested for antimicrobial , compound production. B. licheniformis (SC-43), B. subtilis (SD-8), and Pantoea sp., SC-AF, in the presence of glycerol and ferric ion, could produce antimicrobial '. compounds when grown within ,biofilms; however, the corresponding shaken flask cultures could not. This effect could be related to oxidative stress defence responses. Pantoea sp., SC-AF produced several antimicrobial compounds active against M luteus, HP-5!6 which were different from previously reported Pantocin antimicrobials. In addition, Pantoea sp., SC-AF produced 'jelly-like' extracellular polysaccharide (EPS) ' on NGF and on the nylon membrane in Air-membrane surface bioreactor (AMS) cultures, along with the production of antimicrobial compounds. Only fructose and cellobiose after acid lysis of EPS of Pantoea sp., SC-AF have been identified. In addition, my study confirmed that sponges accommodate large amounts of uncultured bacteria, whose metabolic capability cannot be explored without cultivation. New cultivation strategies should be investigated and biofilm-based culture techniques incorporated in the future search for novel antibiotics.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available