Hou, Yu
[Author]
;
Mittag, Maria
[Degree supervisor];
Kreimer, Georg
[Degree supervisor];
Furch, Alexandra C. U.
[Degree supervisor]Friedrich-Schiller-Universität Jena
Characterization of secondary metabolites and signaling pathways involved in microalgal-bacterial interactions
University thesis:
Dissertation, Friedrich-Schiller-Universität Jena, 2023
Footnote:
Kumulative Dissertation, enthält Zeitschriftenaufsätze
Tag der Verteidigung: 03.08.2023
Zusammenfassungen in deutscher und englischer Sprache
Description:
A soil bacterium Pseudomonas protegens Pf-5 has antagonistic effects on the green microalga Chlamydomonas reinhardtii. P. protegens triggers cytosolic Ca2+ elevations in C. reinhardtii by using a mixture of secondary metabolites. Their IC50 values causing immobilization of the algal cells are in accordance with cytosolic Ca2+ elevations. The cyclic lipopeptide orfamide A causes the strongest immobilization with an IC50 value of only 4.1 µM, which can elevate the cytosolic Ca2+ and deflagellates the algal cells within 1 minute. We further investigated orfamide A triggered effects by using a series of chemically synthesized derivatives. The entire structure of orfamide A, the length of its N-terminal fatty acid tail as well as the stereochemistry of certain amino acids of orfamide A play key roles in its biological activities regarding Ca2+ signatures and deflagellation. Recently, we also performed an alanine scan, showing that most of the amino acids of orfamide A are relevant to maintain its biological activities. Interestingly, two Ca2+ signalling pathways are indicated by our studies. One is involved in the loss of cytosolic Ca2+ elevation and deflagellation. The other triggers a similar Ca2+ response than isolated orfamide A but causes significantly lower deflagellation rates. Using a modulator of Ca2+ channels and knock-out mutants, we found that at least four TRP-type Ca2+ channels (TRP5, TRP11, TRP15 and TRP22) are involved in orfamide A triggered deflagellation.