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Oxidative stress and starvation in Dinoroseobacter shibae: the role of extrachromosomal elements.

Soora M, Tomasch J, Wang H, Michael V, Petersen J, Engelen B, Wagner-Döbler I, Cypionka H - Front Microbiol (2015)

Bottom Line: However, light exposure results in the production of cytotoxic reactive oxygen species in AAPs.The observed decrease of gene expression was not due to plasmid loss, as all five ECRs were maintained in the cells.Interestingly, the genes on the 72-kb chromid were the least downregulated, and one region with genes of the oxygen stress response and a light-dependent protochlorophyllide reductase of cyanobacterial origin was strongly activated under the light/dark cycle.

View Article: PubMed Central - PubMed

Affiliation: Institute for Chemistry and Biology of the Marine Environment (ICBM), Carl-von-Ossietzky University of Oldenburg Oldenburg, Germany.

ABSTRACT
Aerobic anoxygenic phototrophic bacteria (AAP) are abundant in the photic zone of the marine environment. Dinoroseobacter shibae, a representative of the Roseobacter group, converts light into additional energy that enhances its survival especially under starvation. However, light exposure results in the production of cytotoxic reactive oxygen species in AAPs. Here we investigated the response of D. shibae to starvation and oxidative stress, focusing on the role of extrachromosomal elements (ECRs). D. shibae possessing five ECRs (three plasmids and two chromids) was starved for 4 weeks either in the dark or under light/dark cycles and the survival was monitored. Transcriptomics showed that on the chromosome genes with a role in oxidative stress response and photosynthesis were differentially expressed during the light period. Most extrachromosomal genes in contrast showed a general loss of transcriptional activity, especially in dark-starved cells. The observed decrease of gene expression was not due to plasmid loss, as all five ECRs were maintained in the cells. Interestingly, the genes on the 72-kb chromid were the least downregulated, and one region with genes of the oxygen stress response and a light-dependent protochlorophyllide reductase of cyanobacterial origin was strongly activated under the light/dark cycle. A Δ72-kb curing mutant lost the ability to survive under starvation in a light/dark cycle demonstrating the essential role of this chromid for adaptation to starvation and oxidative stress. Our data moreover suggest that the other four ECRs of D. shibae have no vital function under the investigated conditions and therefore were transcriptionally silenced.

No MeSH data available.


Related in: MedlinePlus

Expression of the regulated locus on the 72-kb chromid. The upper bar chart illustrates the differential expression of the regulated locus on the 72-kb chromid (Dshi_4160-4172). In the lower panel, the light dependent chlorophyllide reductase (LPOR) and genes that have been found to be part of the oxidative stress response (Tomasch et al., 2011) are highlighted in green and red colors respectively.
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Figure 4: Expression of the regulated locus on the 72-kb chromid. The upper bar chart illustrates the differential expression of the regulated locus on the 72-kb chromid (Dshi_4160-4172). In the lower panel, the light dependent chlorophyllide reductase (LPOR) and genes that have been found to be part of the oxidative stress response (Tomasch et al., 2011) are highlighted in green and red colors respectively.

Mentions: The observed bias was least pronounced for the 72-kb chromid with log2-fold changes not exceeding -1 under both conditions. The upregulated genes on this chromid (see above) were located in one particular region (Dshi_4160–Dshi_4172, Figure 4). Interestingly one gene coding for a light-dependent protochlorophyllide reductase (Dshi_4160; EC 1.3.1.33), providing an alternative for catalyzing the second to last step of chlorophyll a biosynthesis, is also part of this region that might play an important role during adaptation to light stress under starvation.


Oxidative stress and starvation in Dinoroseobacter shibae: the role of extrachromosomal elements.

Soora M, Tomasch J, Wang H, Michael V, Petersen J, Engelen B, Wagner-Döbler I, Cypionka H - Front Microbiol (2015)

Expression of the regulated locus on the 72-kb chromid. The upper bar chart illustrates the differential expression of the regulated locus on the 72-kb chromid (Dshi_4160-4172). In the lower panel, the light dependent chlorophyllide reductase (LPOR) and genes that have been found to be part of the oxidative stress response (Tomasch et al., 2011) are highlighted in green and red colors respectively.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4373377&req=5

Figure 4: Expression of the regulated locus on the 72-kb chromid. The upper bar chart illustrates the differential expression of the regulated locus on the 72-kb chromid (Dshi_4160-4172). In the lower panel, the light dependent chlorophyllide reductase (LPOR) and genes that have been found to be part of the oxidative stress response (Tomasch et al., 2011) are highlighted in green and red colors respectively.
Mentions: The observed bias was least pronounced for the 72-kb chromid with log2-fold changes not exceeding -1 under both conditions. The upregulated genes on this chromid (see above) were located in one particular region (Dshi_4160–Dshi_4172, Figure 4). Interestingly one gene coding for a light-dependent protochlorophyllide reductase (Dshi_4160; EC 1.3.1.33), providing an alternative for catalyzing the second to last step of chlorophyll a biosynthesis, is also part of this region that might play an important role during adaptation to light stress under starvation.

Bottom Line: However, light exposure results in the production of cytotoxic reactive oxygen species in AAPs.The observed decrease of gene expression was not due to plasmid loss, as all five ECRs were maintained in the cells.Interestingly, the genes on the 72-kb chromid were the least downregulated, and one region with genes of the oxygen stress response and a light-dependent protochlorophyllide reductase of cyanobacterial origin was strongly activated under the light/dark cycle.

View Article: PubMed Central - PubMed

Affiliation: Institute for Chemistry and Biology of the Marine Environment (ICBM), Carl-von-Ossietzky University of Oldenburg Oldenburg, Germany.

ABSTRACT
Aerobic anoxygenic phototrophic bacteria (AAP) are abundant in the photic zone of the marine environment. Dinoroseobacter shibae, a representative of the Roseobacter group, converts light into additional energy that enhances its survival especially under starvation. However, light exposure results in the production of cytotoxic reactive oxygen species in AAPs. Here we investigated the response of D. shibae to starvation and oxidative stress, focusing on the role of extrachromosomal elements (ECRs). D. shibae possessing five ECRs (three plasmids and two chromids) was starved for 4 weeks either in the dark or under light/dark cycles and the survival was monitored. Transcriptomics showed that on the chromosome genes with a role in oxidative stress response and photosynthesis were differentially expressed during the light period. Most extrachromosomal genes in contrast showed a general loss of transcriptional activity, especially in dark-starved cells. The observed decrease of gene expression was not due to plasmid loss, as all five ECRs were maintained in the cells. Interestingly, the genes on the 72-kb chromid were the least downregulated, and one region with genes of the oxygen stress response and a light-dependent protochlorophyllide reductase of cyanobacterial origin was strongly activated under the light/dark cycle. A Δ72-kb curing mutant lost the ability to survive under starvation in a light/dark cycle demonstrating the essential role of this chromid for adaptation to starvation and oxidative stress. Our data moreover suggest that the other four ECRs of D. shibae have no vital function under the investigated conditions and therefore were transcriptionally silenced.

No MeSH data available.


Related in: MedlinePlus