Funktionelle Genomanalyse des Purinverwerters Clostridium acidurici 9a

Functional genome analysis of the purine-utilizing bacterium Clostridium acidurici 9a

by Katrin Hartwich
Doctoral thesis
Date of Examination:2012-12-05
Date of issue:2013-02-20
Advisor:Prof. Dr. Rolf Daniel
Referee:Prof. Dr. Rolf Daniel
Referee:Prof. Dr. Gerhard Gottschalk
Persistent Address: http://dx.doi.org/10.53846/goediss-3739

 

 

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Abstract

English

Clostridium acidurici is an anaerobic, homoacetogenic bacterium, which is able to use purines such as uric acid as sole carbon, nitrogen, and energy source. Together with the two other known purinolytic clostridia C. cylindrosporum and C. purinilyticum, it served as a model organism to investigate the fermentation of purines. Here, the first complete sequence and analysis of a genome derived from a purinolytic Clostridium is presented. The genome of C. acidurici 9a consists of one chromosome (3,105,335 bp) and one small circular plasmid (2,913 bp). The lack of candidate genes encoding glycine reductase, the key enzyme of the glycine reductase pathway of purine-utilizing clostridia, indicates that C. acidurici 9a uses the energetically less favorable glycine-serine-pyruvate pathway for glycine degradation. In accordance with the specialized lifestyle and the corresponding narrow substrate spectrum of C. acidurici 9a, the number of genes involved in carbohydrate transport and metabolism is significantly lower than in other clostridia such as C. acetobutylicum, C. saccharolyticum, and C. beijerinckii. Besides purines, the only other substrate that can be degraded by C. acidurici is glycine, but growth on this amino acid only occurs in the presence of a fermentable purine. Nevertheless, the addition of glycine resulted in increased transcription levels of genes encoding enzymes involved in the glycine-serine-pyruvate pathway such as serine hydroxymethyl transferase and acetate kinase, whereas the transcription levels of formate dehydrogenase-encoding genes decreased. Sugars could not be utilized by C. acidurici but the full genetic repertoire for glycolysis was detected. Additionally, genes encoding enzymes that mediate resistance against several antimicrobials and metals were identified in the genome sequence and a high resistance of C. acidurici 9a towards bacitracin, acriflavine and azaleucine was experimentally confirmed.
Keywords: Clostridium acidurici; glycine reductase; genome sequence; purine degradation; uric acid fermentation; antibiotic resistance; copper homeostasis; cop operon
Schlagwörter: Clostridium acidurici; Glycin-Reduktase; Genomsequenz; Purinabbau; Harnsäure-Fermentation; Antibiotika-Resistenz; Kupfer-Homeostase; cop-Operon
 
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