The response of anoxygenic photosynthetic bacteria to singlet oxygen
Final Report Abstract
Work in this project contributed to a substantial advance in our knowledge on the singlet oxygen response in phototrophic bacteria. Our global analyses revealed that singlet oxygen induces genes for diverse defense mechanisms: peroxide-, sufoxide-, and methylglyocal detoxification, protein quality control and turn-over, singlet oxygen quenching, transport systems (e.g. to remove toxic products), redox and iron homeostasis. Many defense mechanisms are glutathion-dependent and some of the newly identified sRNAs influence the glutathion metabolism. The alternative sigma factors RpoHI and RpoHII were identified as important protein regulators of the singlet oxygen response and RpoHII was shown to be activated by RpoE in a sigma factor cascade. Our work also revealed that RpoE is activated by proteolytic degradation of its anti-sigma factor ChrR. DegS and RseP homolgs were identified as proteases with a major role in ChrR degradation. In E. coli the anti-sigma factor RseA of RpoE is degraded by these two proteases. Despite these similarities there are however significant differences in the role of RpoE in E. coli and R. sphaeroides. RNAseq analyses identified several sRNAs, which are induced by singlet oxygen. Therefore it was not surprising that the RNA chaperone Hfq has an important role in the photooxidative stress response. Some of the singlet oxygen induced RNAs were studied in more detail. SurS is directly induced by RpoE and also encodes a small peptide. It influences expression of many genes with a role in sulfur-metabolism and affects the glutathion pool. SorY is induced by RpoHII and interacts with the mRNA for a metabolite transporter. We showed that SorY is involved in a metabolic shift which leads to increased production of NADPH and reduced production of NADH. As electron donor in the respiratory chain NADH contributes to the production of reactive oxygen species, while NADPH is required in the oxidative stress response (e.g. glutathion and thioredoxin production). This finding assigned a new function for an sRNA. Despite the significant advance in the project, there are several interesting open questions: The role of the sRNAs Rss2461 and Rss6082 is still not understood. Our data suggest that some of the sRNAs influence the levels of other sRNAs which are induced by singlet oxygen but the underlying mechanisms are still obscure. Likewise the function of the OmpR homolog and of RSP_1409, two proteins which are strongly induced by singlet oxygen is still obscure.
Publications
- (2009) Photooxidative stress induced and abundant small RNAs in Rhodobacter sphaeroides. Mol. Microbiol. 74: 1497-1512
Berghoff, B. A., Glaeser, J., Sharma, C., Vogel, J., Klug G.
- (2009) RpoHII activates oxidative stress defence systems and is controlled by RpoE in the singlet oxygen dependent response in Rhodobacter sphaeroides. J. Bacteriol. 191:220-230
Nuss, A.M. Glaeser, J., Klug, G.
- (2010) Overlapping alternative sigma factor regulons in the response to singlet oxygen in Rhodobacter sphaeroides. J. Bacteriol. 192: 2613-2623
Nuss, A.M., Glaeser, J., Berghoff, B.A., Klug, G.
- (2011) Aerobic photosynthesis and photooxidative stress: A particular challenge for Roseobacter. Environm. Microbiol. 13: 775-792
Berghoff, B.A., Glaeser, J., Nuss, A.N., Zobawa, M., Lottspeich, F., Klug, G.
- (2011) Contribution of Hfq to photooxidative stress resistance and global regulation in Rhodobacter sphaeroides. Mol. Microbiol. 80: 1479-1495
Berghoff, B.A., Glaeser, J., Sharma, C.M., Zobawa, M., Lottspeich, F., Vogel, J., Klug, G.
- (2011) Singlet oxygen stress in microorganisms. In R. Poole, R.K. (ed): Adv. in Microb. Physiol. Vol. 58 (Amsterdam), pp. 141-173
Glaeser, J., Nuss, A.M., Berghoff, B.A., Klug, G.
- (2011) Small RNAs with a role in the oxidative stress response in bacteria. In: Marchfelder, A., Hess, W. eds.: Regulatory RNAs in prokaryotes. Springer Verlag
Berghoff, B. A., Klug, G.
- (2013) DegS and RseP homologous proteases are involved in singlet oxygen dependent activation of RpoE in Rhodobacter sphaeroides. PLoS ONE 8: e79520
Nuss, A.M., Adnan, F., Weber, L., Berghoff, B.A., Glaeser, J., Klug, G.
(See online at https://doi.org/10.1371/journal.pone.0079520) - (2013) Integrative "Omics"-approach discovers dynamic and regulatory features of bacterial stress responses. PLoS Genetics 9: e 1003576
Berghoff, B.A., Konzer, A., Mank, N.N., Looso, M., Rische, T., Förstner, K.U., Krüger, M., Klug, G.
(See online at https://doi.org/10.1371/journal.pgen.1003576) - (2014) Riboregulators and the role of Hfq in photosynthetic bacteria. RNA Biology 11: 413-426
Hess, W., Berghoff, B., Wilde, A., Steglich, C., Klug, G.
(See online at https://doi.org/10.4161/rna.28035) - (2015) The sRNA SorY confers resistance during photooxidative stress by affecting a metabolite transporter in Rhodobacter sphaeroides. RNA Biology, Volume 12, 2015 - Issue 5, 569-577
Adnan F, Weber L, Klug G
(See online at https://doi.org/10.1080/15476286.2015.1031948)
