Five-Gene Cluster in Clostridium thermoaceticum Consisting of Two Divergent Operons Encoding Rubredoxin Oxidoreductase, Rubredoxin and

Rubrerythrin-Type A Flavoprotein- High-Molecular-Weight Rubredoxin

Das, Amaresh, Eric D. Coulter, Donald M. Kurtz Jr., and Lars G. Ljungdahl (Mar. 2001) Journal of Bacteriology

183, 1560-1567

Background Info

• Anaerobic and microaerophilic bacteria’s O2 toleration.

• Presence of SOD and catalase in aerobes.

• Absence of SOD and catalase in anaerobes.

• Rbr and Rbo indicated in oxidative stress protection.

• Clostridium thermoaceticum is an obligately anaerobic bacteria containing genes that code for Rbr and Rbo.

Why?

• Clostridium thermoaceticum is an obligately anaerobic bacteria containing genes that code for Rbr and Rbo.

• Also codes for Rub, Hrb, and FprA.• Previously Rub, Rbr, Rbo, and FprA

have been implicated in oxidative stress protection occurring in tandem pairs not a whole cluster.

• None of theses genes except Rub have previously been found in acetogenic bacteria.

Experimental Techniques• SDS-PAGE • Northern and

Western blots• Fast protein liquid

chromatography filtration

Results

• SDS-PAGE of the purified recombinant proteins.

Results

Northern blots of all RNA that was isolated from the C. thermoaceticum and E. coli after hybridization.

Conclusions• Successful characterization of a five gene

cluster containing two divergent operons.

• First evidence for the presence of Rbr, Rbo, and FprA in acetogenic bacterium.

• Expression of Rbr, Rbo, and FprA are coregulated and suggest a cooperative role in oxidative stress protection.

Conclusions

• C. thermoaceticum lacks SOD or catalase, yet is capable of growth in trace amounts of O2 without the presence of a reducing agent.

• This oxygen toleration seems to result from the expression of the five gene cluster which was characterized here.

Questions?