Jing ZHANG Investigation into quorum sensing in the microalga Chlorella vulgaris and the yeast Saccharomyces cerevisiae

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1 Quorum Sensing What is quorum sensing? Investigation into quorum sensing in the microalga Chlorella vulgaris and the yeast Saccharomyces cerevisiae Communication between microorganisms With own species or with other species Could be positive or negative Observed with bacteria and with yeasts Examples: Jing ZHANG Directeur de thèse: Behnam TAIDI Bacteria (lactones, peptide etc..) Encadrant: Pin LU Yeast and yeast (killer factor, NH3) Fungi (pheromones) Slime molds (Fuligo septica, camp) Etc. 1

2 Introduction Why do we study mixed cultures? Alternative way to bring functionality ( to GMO) Natural was CH 4 anaerobic digestion Sewage treated 2

3 Introduction What is quorum sensing? Communication between microorganisms With own species or with other species Could be positive or negative Observed with bacteria and with yeasts Examples: Bacteria (peptide, Acyl-L- homoserine lactone etc..) Yeast (NH 3 ) Algae and bacteria (Pheromones) Slime molds (Fuligo septica, camp) 3

4 Plan of thesis Definition of the base methods Physical contact of the two organisms Gaseous/Soluble contact of the two organisms Model development in order to distinguish and explain with confidence Hunt for possible molecules (analytical or library based) 4

5 Materials: Two model organisms Saccharomyces cerevisiae Used for bread, wine, beer, cider and bioethanol Extensively studied and used in industry First eukaryote to have been completely sequenced genetically (1996) Quorum sensing molecules: Ammonia, Farnesol, Tyrosol etc Chlorella vulgaris One of the most extensively studied microalgae Approved for human and animal nutrition Biofuel production 5

6 Modes of metabolism S. cerevisiae - Fermentation - Respiration - Facultative anaerobic C. vulgaris - Photosythesis - Heterotrophy - Mixotrophy Hammed, A et al Growth regime and environmental remediation of microalgae A. M. Hammed, S. K. Prajapati, S. Simsek, and H. Simsek, Growth regime and environmental remediation of microalgae, vol. 31, no. 3, pp ,

7 Methods: ZEISS Axio Zoom.V16 Apotome2 01/18/2017 7

8 Image processing: Colony Area (2D) Converting the format Morphological closing Binary (Otsu's method) Calculating the area 8

9 Image processing: Colony Volume (3D) Optical sectioning, Converting the format Binary (Mean method, constant) Morphological closing Stitching Median Filter 3D Reconstruction Calculating the volume 9

10 Results: C. vulgaris colony growth under different conditions 10

11 Conclusions Globally, the methods to be used during the PhD have been defined Standard growth conditions on solid media; Inoculating techniques, incubating conditions; Gathering growth data (2D and 3D images) by fluorescence zoom microscope; Image processing(2d colony area and 3D colony volume). 11

12 Perspectives Determination of relation between 2D and 3D growth and population Mixed colonies Colonies at proximity Modelling the growth of colony Possible molecules (volatile or soluble) 12

13 Thank you for your attention! 13