Kooperativer Bibliotheksverbund

Berlin Brandenburg

and
and

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
Language
Year
  • 1
    Language: English
    In: Microbiology (Reading, England), June 2005, Vol.151(Pt 6), pp.1927-38
    Description: In Rhodobacter sphaeroides, carotenoids are essential constituents of the photosynthetic apparatus and are assumed to prevent the formation of singlet oxygen by quenching of triplet bacteriochlorophyll a (BChl a) in vivo. It was shown that small amounts of singlet oxygen are generated in vivo by incubation of R. sphaeroides under high light conditions. However, growth and survival rates were not affected. Higher amounts of singlet oxygen were generated by BChl a in a carotenoid-deficient strain and led to a decrease in growth and survival rates. The data support earlier results on the pivotal role of carotenoids in the defence against stress caused by singlet oxygen. Results obtained under photo-oxidative stress conditions with strains impaired in carotenoid synthesis suggest that sphaeroidene and neurosporene provide less protection against methylene-blue-generated singlet oxygen than sphaeroidenone in vivo. Despite their protective function against singlet oxygen, relative amounts of carotenoids did not accumulate in R. sphaeroides wild-type cultures under photo-oxidative stress, and relative mRNA levels of phytoene dehydrogenase and sphaeroidene monooxygenase did not increase. In contrast, singlet oxygen specifically induced the expression of glutathione peroxidase and a putative Zn-dependent hydrolase, but mRNA levels of hydrogen-peroxide-degrading catalase E were not significantly affected by photo-oxidative stress. Based on these results, it is suggested that singlet oxygen acts as a specific signal for gene expression in R. sphaeroides. Presumably transcriptional regulators exist to specifically induce the expression of genes involved in the response to stress caused by singlet oxygen.
    Keywords: Adaptation, Physiological ; Gene Expression Regulation, Bacterial ; Oxidative Stress ; Carotenoids -- Physiology ; Rhodobacter Sphaeroides -- Physiology
    ISSN: 1350-0872
    E-ISSN: 14652080
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 2
    Language: English
    In: Journal of Bacteriology, May, 2010, Vol.192(9-10), p.2613(11)
    Description: Organisms performing photosynthesis in the presence of oxygen have to cope with the formation of highly reactive singlet oxygen ([sup.1][O.sub.2]) and need to mount an adaptive response to photooxidative stress. Here we show that the alternative sigma factors [RpoH.sub.I] and [RpoH.sub.II] are both involved in the [sup.1][O.sub.2] response and in the heat stress response in Rhodobacter sphaeroides. We propose [RpoH.sub.II] to be the major player in the [sup.1][O.sub.2] response, whereas [RpoH.sub.I] is more important for the heat stress response. Mapping of the 5' ends of [RpoH.sub.II]- and also [RpoH.sub.I]/[RpoH.sub.II]-dependent transcripts revealed clear differences in the -10 regions of the putative promoter sequences. By using bioinformatic tools, we extended the [RpoH.sub.II] regulon, which includes genes induced by [sup.1][O.sub.2] exposure. These genes encode proteins which are, e.g., involved in methionine sulfoxide reduction and in maintaining the quinone pool. Furthermore, we identified small RNAs which depend on [RpoH.sub.I] and [RpoH.sub.II] and are likely to contribute to the defense against photooxidative stress and heat stress. doi: 10.1128/JB.01605-09
    Keywords: Active Oxygen -- Physiological Aspects ; Promoters (Genetics) -- Physiological Aspects ; Proteobacteria -- Genetic Aspects ; Proteobacteria -- Physiological Aspects
    ISSN: 0021-9193
    Source: Cengage Learning, Inc.
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 3
    Language: English
    In: Molecular microbiology, June 2011, Vol.80(6), pp.1479-95
    Description: The photosynthetic alphaproteobacterium Rhodobacter sphaeroides has to cope with photooxidative stress that is caused by the bacteriochlorophyll a-mediated formation of singlet oxygen ((1)O(2)). Exposure to (1)O(2) induces the alternative sigma factors RpoE and RpoH(II) which then promote transcription of photooxidative stress-related genes, including small RNAs (sRNAs). The ubiquitous RNA chaperone Hfq is well established to interact with and facilitate the base-pairing of sRNAs and target mRNAs to influence mRNA stability and/or translation. Here we report on the pleiotropic phenotype of a Δhfq mutant of R. sphaeroides, which is less pigmented, produces minicells and is more sensitive to (1)O(2). The higher (1)O(2) sensitivity of the Δhfq mutant is paralleled by a reduced RpoE activity and a disordered induction of RpoH(II)-dependent genes. We used co-immunoprecipitation of FLAG-tagged Hfq combined with RNA-seq to identify association of at least 25 sRNAs and of mRNAs encoding cell division proteins and ribosomal proteins with Hfq. Remarkably, 〉 70% of the Hfq-bound sRNAs are (1)O(2)-affected. Proteomics analysis of the Hfq-deficient strain revealed an impact of Hfq on amino acid transport and metabolic functions. Our data demonstrate for the first time an involvement of Hfq in regulation of photosynthesis genes and in the photooxidative stress response.
    Keywords: Gene Expression Regulation, Bacterial ; Oxidative Stress ; Protein Binding ; Bacterial Proteins -- Metabolism ; Host Factor 1 Protein -- Metabolism ; Rhodobacter Sphaeroides -- Metabolism
    ISSN: 0950382X
    E-ISSN: 1365-2958
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 4
    In: The Journal of Bacteriology, 2010, Vol. 192(10), p.2613
    Description: Organisms performing photosynthesis in the presence of oxygen have to cope with the formation of highly reactive singlet oxygen (...) and need to mount an adaptive response to photooxidative stress. Here we show that the alternative sigma factors RpoH... and RpoH... are both involved in the... response and in the heat stress response in Rhodobacter sphaeroides. We propose RpoH...I to be the major player in the ... response, whereas RpoH... is more important for the heat stress response. Mapping of the 5' ends of RpoH...- and also RpoH.../RpoH...-dependent transcripts revealed clear differences in the -10 regions of the putative promoter sequences. By using bioinformatic tools, we extended the RpoH... regulon, which includes genes induced by ... exposure. These genes encode proteins which are, e.g., involved in methionine sulfoxide reduction and in maintaining the quinone pool. Furthermore, we identified small RNAs which depend on RpoH... and RpoH... and are likely to contribute to the defense against photooxidative stress and heat stress. (ProQuest: ... denotes formulae/symbols omitted.)
    Keywords: Bacteria ; Oxygen ; Photosynthesis ; Gene Expression ; Proteins ; Ribonucleic Acid–RNA ; Bacteriology;
    ISSN: 0021-9193
    ISSN: 00219193
    E-ISSN: 10985530
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 5
    Language: English
    In: PLoS ONE, 2014, Vol. 9(3), p. e92518
    Description: Light excitation of humic matter generates reactive oxygen species (ROS) in surface waters of aquatic ecosystems. Abundant ROS generated in humic matter rich lakes include singlet oxygen (O-1(2)) and hydrogen peroxide (H2O2). Because these ROS differ in half-life time and toxicity, we compared their effects on microbial activity (C-14-Leucine incorporation) and bacterial community composition (BCC) in surface waters of humic Lake Grosse Fuchskuhle (North-eastern Germany). For this purpose, experiments with water samples collected from the lake were conducted in July 2006, September 2008 and August 2009. Artificially increased O-1(2) and H2O2 concentrations inhibited microbial activity in water samples to a similar extent, but the effect of the respective ROS on BCC varied strongly. BCC analysis by 16S rRNA gene clone libraries and RT-PCR DGGE revealed ROS specific changes in relative abundance and activity of major bacterial groups and composition of dominating phylotypes. These changes were consistent in the three experiments performed in different years. The relative abundance of Polynucleobacter necessarius, Limnohabitans-related phylotypes (Betaproteobacteria), and Novosphingobium acidiphilum (Alphaproteobacteria) increased or was not affected by photo-sensitized O-1(2) exposure, but decreased after H2O2 exposure. The opposite pattern was found for Actinobacteria of the freshwater AcI-B cluster which were highly sensitive to O-1(2) but not to H2O2 exposure. Furthermore, group-specific RT-PCR DGGE analysis revealed that particle-attached P. necessarius and Limnohabitans-related phylotypes exhibit higher resistance to O-1(2) exposure compared to free-living populations. These results imply that O-1(2) acts as a factor in niche separation of closely affiliated Polynucleobacter and Limnohabitans-related phylotypes. Consequently, oxidative stress caused by photochemical ROS generation should be regarded as an environmental variable determining abundance, activity, and phylotype composition of environmentally relevant bacterial groups, in particular in illuminated and humic matter rich waters.
    Keywords: Natural Sciences ; Biological Sciences ; Naturvetenskap ; Biologiska Vetenskaper
    ISSN: 1932-6203
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 6
    Language: English
    In: Microbiology (Reading, England), December 2011, Vol.157(Pt 12), pp.3306-13
    Description: Metal homeostasis is important in all living cells in order to provide sufficient amounts of metal ions for biological processes but to prevent toxic effects by excess amounts. Here we show that the gene product of RSP_2889 of the facultatively photosynthetic bacterium Rhodobacter sphaeroides is homologous to CueR, a regulator of copper metabolism in Escherichia coli and other bacteria. CueR binds to the promoter regions of genes for a copper-translocating ATPase and for a copper chaperone and is responsible for their high expression when cells are exposed to elevated levels of copper ions. While deletion of RSP_2889 has no significant effect on copper resistance, expression from a low-copy-number plasmid mediates increased sensitivity to copper.
    Keywords: Gene Expression Regulation, Bacterial ; Bacterial Proteins -- Genetics ; Copper -- Metabolism ; DNA-Binding Proteins -- Genetics ; Rhodobacter Sphaeroides -- Genetics
    ISSN: 13500872
    E-ISSN: 1465-2080
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 7
    Language: English
    In: PLoS ONE, 2013, Vol.8(11), pp.e79520
    Description: Singlet oxygen (O-1(2)) is the main agent of photooxidative stress and is generated by photosensitizers as (bacterio) chlorophylls. It leads to the damage of cellular macromolecules and therefore photosynthetic organisms have to mount an adaptive response to O-1(2) formation. A major player of the photooxidative...
    Keywords: Natural Sciences ; Naturvetenskap
    ISSN: 1932-6203
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 8
    In: Applied and Environmental Microbiology, 2004, Vol. 70(8), p.4821
    ISSN: 0099-2240
    ISSN: 00992240
    Source: American Society of Microbiology
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 9
    Language: English
    In: Journal of Bacteriology, Jan, 2009, Vol.191(1-2), p.220(11)
    Description: Photosynthetic organisms need defense systems against photooxidative stress caused by the generation of highly reactive singlet oxygen ([sup.1][O.sub.2]). Here we show that the alternative sigma factor Rpo[H.sub.II] is required for the expression of important defense factors and that deletion of rpo[H.sub.II] leads to increased sensitivity against exposure to [.sup.1][O.sub.2] and methylglyoxal in Rhodobacter sphaeroides. The gene encoding Rpo[H.sub.II] is controlled by RpoE, and thereby a sigma factor cascade is constituted. We provide the first in vivo study that identifies genes controlled by an Rpo[H.sub.II]-type sigma factor, which is widely distributed in the Alphaproteobacteria. Rpo[H.sub.II]-dependent genes encode oxidative-stress defense systems, including proteins for the degradation of methylglyoxal, detoxification of peroxides, [sup.1][O.sub.2] scavenging, and redox and iron homeostasis. Our experiments indicate that glutathione (GSH)-dependent mechanisms are involved in the defense against photooxidative stress in photosynthetic bacteria. Therefore, we conclude that systems pivotal for the organism's defense against photooxidative stress are strongly dependent on GSH and are specifically recognized by Rpo[H.sub.II] in R. sphaeroides.
    Keywords: Photosynthetic Bacteria -- Physiological Aspects ; Oxidative Stress -- Research
    ISSN: 0021-9193
    Source: Cengage Learning, Inc.
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 10
    Language: English
    In: Applied and environmental microbiology, August 2004, Vol.70(8), pp.4821-30
    Description: Motile phototrophic consortia are highly regular associations in which numerous cells of green sulfur bacteria surround a flagellated colorless beta-proteobacterium in the center. To date, seven different morphological types of such consortia have been described. In addition, two immotile associations involving green sulfur bacteria are known. By employing a culture-independent approach, different types of phototrophic consortia were mechanically isolated by micromanipulation from 14 freshwater environments, and partial 16S rRNA gene sequences of the green sulfur bacterial epibionts were determined. In the majority of the lakes investigated, different types of phototrophic consortia were found to co-occur. In all cases, phototrophic consortia with the same morphology from the same habitat contained only a single epibiont phylotype. However, morphologically indistinguishable phototrophic consortia collected from different lakes contained different epibionts. Overall, 19 different types of epibionts were detected in the present study. Whereas the epibionts within one geographic region were very similar (Dice coefficient, 0.582), only two types of epibionts were found to occur on both the European and North American continents (Dice coefficient, 0.190). None of the epibiont 16S rRNA gene sequences have been detected so far in free-living green sulfur bacteria, suggesting that the interaction between epibionts and chemotrophic bacteria in the phototrophic consortia is an obligate interaction. Based on our phylogenetic analysis, the epibiont sequences are not monophyletic. Thus, the ability to form symbiotic associations either arose independently from different ancestors or was present in a common ancestor prior to the radiation of green sulfur bacteria and the transition to the free-living state in independent lineages. The present study thus demonstrates that there is great diversity and nonrandom geographical distribution of phototrophic consortia in the natural environment.
    Keywords: Ecosystem ; Evolution, Molecular ; Genetic Variation ; Symbiosis ; Betaproteobacteria -- Classification ; Chlorobi -- Classification ; Fresh Water -- Microbiology
    ISSN: 0099-2240
    E-ISSN: 10985336
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. Further information can be found on the KOBV privacy pages