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| Identifier |
000418830 |
| Title |
Βιοενεργητική μελέτη της ακραιοφιλικής συμπεριφοράς του χλωροφύκους Trebouxia crenulata στα πλαίσια συμβίωσής του με μεθυλοβακτήριο |
| Alternative Title |
Bioenergetic study of the extremophilic behavior of the green alga Trebouxia crenulata in symbiosis with a methylobacterium |
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Author
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Τύμπα Λύδα-Ελένη Λ.
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Thesis advisor
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Κοτζαμπάσης, Κυριάκος
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Thesis advisor
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Πυρίντζος, Στέργιος
Φλεμετάκης, Εμμανούηλ
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| Abstract |
This work focuses on the extremophilic behavior of the unicellular green alga
Trebouxia crenulata, which is the photobiont of Ramalina capitata lichen species.
The algal strain that was isolated from the lichen thallus, showed an unexpected
mutualistic interaction with a potentially photosynthetic bacterial strain, as derived
from the spectral characterization of its pigments. The populations of the two
interacting microorganisms coexisted and although each population outnumbered the
other under different circumstances, both of them remained viable and robust. A rise
in the bacterial population was able to accelerate the otherwise low growth rate of the
algae. In order to elucidate whether the observed interaction affects the
extremotolerance of the algae in a positive or negative fashion, we comparatively
investigated the response of this mutualistic scheme to extreme salinity, low
temperature and dessication, in contrast to the response of each partner separately.
Interestingly, the mutualistic scheme exhibited remarkable tolerance to salinity up to
50‰, since, after 66 hours of incubation in the respective medium, the photosynthetic
apparatus of the algae remained completely functional, while the bacteria showed
normal growth on petri dishes. Extreme low temperature (-196 oC/ 77K) and
dessication had the same effect on both microorganisms, indicating compatibility in
their extremotolerance ranges. The bacterial strain belongs to the genus
Methylobacterium, according to its 16S rRNA sequenced region, while its species
specific rpoΒ region sequence shows 94% similarity with the respective region of
Methylobacterium populi. This particular species has been described to promote plant
growth through producing IAA and detoxifying its environment. In the repetition of
the above abiotic stress experiments on axenic cultures of T. crenulata (after
successfully isolating the strain), the algae failed to cope with the extreme conditions
adequately to the mutualistic scheme. As is evident from the overall results, the
studied bacterial-algal interaction has a positive impact on the extremotolerance of T.
crenulata. Moreover, the mutualistic scheme as well as the axenic algal culture failed
to produce hydrogen (H2) in anaerobic conditions. This is in accordance with previous
results from our lab, which indicate that lichen species of the genus Ramalina tested
for hydrogen production, were the only ones that failed to exhibit considerable
amounts of hydrogen. In order to propose a specific mechanism of the above
mutualism, in addition to elucidating the possibility of the two microorganisms
coexisting in lichen microecosystems, thorough molecular and biochemical analysis is
to be performed.
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| Language |
Greek |
| Subject |
Extremotolerance |
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Ακραιοφιλία |
| Issue date |
2018-11-23 |
| Collection
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School/Department--School of Sciences and Engineering--Department of Biology--Post-graduate theses
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Type of Work--Post-graduate theses
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| Permanent Link |
https://elocus.lib.uoc.gr//dlib/d/f/7/metadata-dlib-1540193791-777003-15135.tkl
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| Views |
271 |
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