Determining the Effects of Lichen and Endolichenic Bacteria Extracts on Pseudomonas aeruginosa Quorum Sensing and Biofilm Form

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Başaran T. I. , Gökalsın B., Sesal N. C.

Ulaslararası İVEK BİO Kongresi 2018, İstanbul, Turkey, 26 - 28 November 2018, pp.15-178

  • Publication Type: Conference Paper / Summary Text
  • City: İstanbul
  • Country: Turkey
  • Page Numbers: pp.15-178


Multidrug resistance in Pseudomonas aeruginosa is constantly increasing and poses a signifcant risk to public
P. aeruginosa is capable of developing into bioflm forms in which they show increase resistance against
antibiotics. Bioflm formation and virulence factors are linked to the mechanism known as Quorum sensing (QS).
QS related genes are regulated by the release of signal molecules and detection of these molecules at the group level
due to bacterial population density. It is thought that QS systems can be inhibited via molecules defned as QS
inhibitors (QSIs). For this purpose, discovering novel natural QSIs is deemed necessary. QSIs can be obtained from
natural sources such as lichens, plants, fungi, bacteria etc. It is well known that lichens produce unique secondary
metabolites and some of them have antimicrobial activities. Lichens, which have symbiotic relations with fungi,
cyanobacteria or algae, also provide special habitats to various bacterial groups. Moreover, these bacteria, called
“endolichenic bacteria” (ELB) live on lichen’s surface and partly within thalli in a competitive environment.
Terefore, ELB should make use of antimicrobial compounds including potential QSIs. To determine QSI potential
of ELB, we isolated ELB species coded TB49 from
Plasmatia glauca and we extracted ethyl acetate cell free
supernatant extracts (CFSE). Dosages were adjusted to 240, 120 and 60 μg/ml. Te extracts were applied on
P. aeruginosa lasB-gfp and rhlA-gfp biosensor strains to observe QS inhibition. P.aeruginosa PAO1 (wild type) strain was
used to determine bioflm inhibition. QS and bioflm inhibition tests were monitored with Cytation 3-multimode
microplate reader (Biotek). For 240 μg/ml CFSE, inhibition ratio was calculated as 66,19% for
lasB-gfp and 27,94%
rhlA-gfp. Biofilm inhibition ratio of CFSE was observed as 55,75 % (±2,5). As a result, CFSE of TB49 has been
observed to be more effective on the
las system than the rhl system. We concluded that, if the concentrations are
higher, inhibition rates may increase. Also we understand that, more effective results can be observed by inhibiting
las and rhl inhibition along with other pathways. Further studies should be considered including determination of
the active metabolite and its effects on human cells.
Pseudomonas aeruginosa, lichen, endolichenic bacteria, quorum sensing, biofilm

Acknowledgement This study
was funded by BAPKO Project No: FEN-C-YLP-131217-0679 We thank TÜBİTAK-BİDEB 2210/C scholarship