Medium-dependent effect of quorum sensing on mixed species biofilm communities
Muhammad Zulfadhly Bin Mohammad Muzaki
Date of Issue2017
School of Biological Sciences
Singapore Centre on Environmental Life Sciences Engineering
Most studies on the effects of quorum sensing on biofilm development have been in single-species biofilms. However, most biofilms in nature are established as a mixed-species community. Here, the effects of quorum sensing are investigated in a mixed-species biofilm comprised of fluorescently-tagged Pseudomonas aeruginosa, Klebsiella pneumoniae and Pseudomonas protegens. The mixed-species biofilms were grown as a static biofilm in both Artificial Sputum Medium (ASM) as well as M9 minimal medium and confocal scanning laser microscopy images were taken. Quorum sensing in P. aeruginosa was shown to be involved in the formation of distinct biofilm structures, co-aggregation between P. aeruginosa and K. pneumoniae as well as competition between P. aeruginosa and P. protegens. This effect however, was only seen in ASM and not in M9 minimal medium. Additionally, analysis of continuous-culture mixed-species biofilm showed that quorum sensing imparts community-level resilience of biofilm to sodium dodecyl sulfate (SDS). In mixed species biofilm containing P. aeruginosa wild-type, biovolume decreased 30.231 ± 3.00% after SDS treatment while biofilm containing P. aeruginosa quorum sensing mutants had a biovolume decrease of 99.68 ± 0.909%. In conclusion, P. aeruginosa quorum sensing affects community-level interactions in mixed-species biofilms and is conditional on the nutrients present in the environment.
Final Year Project (FYP)
Nanyang Technological University