A study of gene expression of Saccharomyces cerevisiae in oscillating continuous cultures using DNA microarray technology [Elektronische Ressource] / von Ahmed Abd Allah Khalil Ahmed

Ahmed Khalil

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• Gesundheit

Informations

• Publié par: gottfried_wilhelm_leibniz_universitat_hannover
• Publié le: 01 janvier 2008
• Nombre de lectures: 55
• Langue: English
• Poids de l'ouvrage: 3 Mo

Extrait

A Study of Gene Expression of Saccharomyces
cerevisiae in Oscillating Continuous Cultures
Using DNA Microarray Technology



Von der Naturwissenschaftlichen Fakultät
der Gottfried Wilhelm Leibniz Universität Hannover






zur Erlangung des Grades
Doktor der Naturwissenschaften
Dr. rer. nat


genehmigte Dissertation



von

M. Sc. in Biochemistry Ahmed Abd Allah Khalil Ahmed


geboren am 04.11.1973


Hannover 2008







































Referent: Prof. Dr. Thomas Scheper

Korreferent: Prof. Dr. Bernd Hitzmann

Tag der Promotion: 14-07-2008


Gedruckt mit Unterstützung des Deutschen Akademischen Austauschdienstes (DAAD)



































Erklärung

Ich versichere, dass ich diese Dissertation selbstständig und nur unter
Verwendung der angegebenen Hilfsmittel und Quellen durchgeführt habe. Diese
Arbeit wurde nicht als Diplomarbeit oder ähnliche Prüfungsarbeit verwendet.

Hannover, Juli 2008
Ahmed Abd Allah Khalil Ahmed







Dedication

I dedicate this work to my family:

My Lovely Mother
My Great Father
My Dear Brother
My Beloved Wife
&
My Beautiful Daughter.

I am always thankful to God for the presence of this family in
my life. They usually support me with endless love and moral
support.

Ahmed Abd Allah Khalil Ahmed



















Acknowledgements

I would like to express my deep thanks to my supervisor Prof. Dr. Thomas Scheper, who
suggested the topic of this thesis, for his continuous support, valuable advices and fatherly
attitude over the past 4 years of my Ph.D. study. Prof. Scheper is not only a great scientist but
also a very caring supervisor. Through these years, he helped me in so many ways to achieve
successfully what I need to accomplish in this thesis work. I feel very grateful to have the
opportunity to work in his research group. What he taught me will surely benefit me
throughout my life. My heartful gratitude is expressed to him.

My Sincere thanks are also for Prof. Dr. Bernd Hitzmann who very kindly agreed to be an
examiner for this work.

I am also very grateful to thank Dr. Frank Stahl for his valuable guidance in the steps of RNA
purification and DNA microarrays preparation, in addition to his reading of the whole work to
help me to be in the best form.

No words can express my deep thanks and appreciation to Diplom. Chem. Bastian Rode who
helped me a lot during all the cultivation steps of this work. He did a great contribution to
achieve a successful continuous cultivation processes.

At the time, I was working in RNA lab; Mr. Martin pähler provided me with valuable
guidance and great technical support to obtain very pure RNA and to understand the DNA
microarray technology. My sincere thanks is expressed to him

I would especially like to thank Dr. Christine Klockow and M.Sc. Cornelia Repenning for
their great contribution in data analysis of all DNA microarrays of this work.

A special thank you must be sent to Mrs. Martina Weiß who helped me easily with the GC
technique.

I am really indebted to all members of Institute of Technical Chemistry, with special thanks
and appreciation to M.Sc. Amer Hakki, M.Sc. Tarek Kandil, M.Sc. Rozan Fatteh and M.Sc.
Moftah Omer for their great help and recommendations especially during writing this work.

I will never forget throughout my life the memory of great men and women who paved the
way for my first steps in the scientific field like my M.Sc. supervisor Prof. Dr. Zeinab El
Dardiri who taught me the basics of biochemistry and scientific research, in addition to Prof.
Dr. Abd El-mouty Azzam who directed me to the Institute of Technical Chemistry, Hannover,
to carry out my Ph.D. research work.

Without love and patience, no work can be performed; I got the real love and the strongest
support to carry out this work from my family; my lovely mother Aisha Ahmed, my great
father Abd Allah Khalil, my dear brother Amged Khalil, my beloved wife Shaimaa Hussein
and my small baby Shahd. They were usually beside me in good times as well as hard times.




Abstract
The yeast Saccharomyces cerevisiae is often considered the most ideal eukaryotic
microorganism for biological studies. The ease of genetic manipulation and cultivation of
yeast allows its use for conveniently analyzing and functionally dissecting gene products from
other eukaryotes. The present study aimed to develop different types of microarrays for the
whole genome expression and specific low denisty oligonucleotides microarrays to follow up
the differential gene expression and regulation for chemostat-cultivated S. cerevisiae (H620)
cells during especially G1 and S-phase events. The cells were cultivated for this aim
continuously on the level of 2L bioreactor and the whole proces was optimized successfully to
the level of 10L. The cells exhibited autonomous oscillations with periodic oxido-reductive
metabolism, when grown aerobically in the continuous culture using glucose as the main
carbon and energy source. The total RNA was isolated from the cells to be used as a starting
material in the cDNA hybridization protocol of the microarrays. RNA was purified using hot
phenol technique and enzymatic lysis method of RNeasy Midi Kit. Both methods were fast,
suitable and reproducible, but the Midi kit was the protcol of choice in further preparations of
the required RNA for the microarray hybridizations because of the higher yield and purity of
its product. The relationship between total RNA inside the cells and the corresponding cell
cycle phases was studied. During the 2L cultivation, the highest yield of RNA was in the
mean time of S-phase (9.4 µg/µl), whereas the lowest value (3.4 µg/µl) during G2/M. During
the 10L cultivation, RNA concentrations were also at their maximum levels at S-phase peaks;
moreover, a doubling in RNA concentration had seen once from 5.5µg/µl during G1 to
10.5µg/µl during the same cycle. A prescreeing step was of great important for the whole
gene expression during G1 and S-phase using the commerial yeast whole genome chip
(MWG PAN yeast arrayII). The results of this screeing showed 532 reproducible genes, of
which 130 genes were up regulated and 402 genes were down regulated. 90 genes, concerned
with essential regulatory events during S. cerevisiae cell cycle, were selected among these
reproducible genes to be used in further production of specific low denisity oligonucleotides
microarrays. Another 50 genes, chosen by department of microbiology, Helmholtz center,
Lepizig, concerned mainly with glucose metabolism, were added to the cell cycle regulatory
genes to sum up 140 genes. This catalog of genes was used successfully to monitor the gene
expression and regulation of 3 sequential cycles of cells collected from 10 L bioreactor. The
cellular regulatory functions of yeast like that of cell wall biogensis, DNA and RNA
synthesis, spindle pole body duplication and protein kinases were monitored easily in
correlation with the metaolic status of cells inside the reactor using this catalog of genes.
i


Zusammenfassung

Die Bäckerhefe S. cerevisiae hat als Modellorganismus für Genexpressionsanalysen mit
DNA-Chips mehrere Vorteile: Sie verbindet als einzelliger Eukaryont eine hohe Ähnlichkeit zu
Säugerzellen mit prokaryontischer Handlichkeit: Hefen besitzen eine kurze Generationszeit (90
min auf Vollmedien mit Glukose als Energiequelle), sind ungiftig und auf preiswerten Medien
auch in großen Mengen (kg-Maßstab) mit geringem apparativem Aufwand leicht anziehbar.
In der vorliegenden Arbeit soll ausgehend von Genexpressionsanalysen synchroner
Hefekulturen auf kommerziellen whole genome arrays ein zellzyklusspezifischer low density
Hefechip entwickelt werden. Hierzu wurden die Hefezellen zunächst kontinuierlich in einem 2 L
Bioreaktor kultiviert. Der vollständige Prozess wurde anschließend erfolgreich auf ein 10 L
Niveau upgescalt. Die Synchronisation von Hefezellen im Bi