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  • 1
    ISSN: 1432-072X
    Keywords: Rhodospirillaceae ; Rhodopseudomonas globiformis ; Sulfate assimilation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Rhodopseudomonas globiformis is able to grow on sulfate as sole source of sulfur, but only at concentrations below 1 mM. Good growth was observed with thiosulfate, cysteine or methionine as sulfur sources. Tetrathionate supported slow growth. Sulfide and sulfite were growth inhibitory. Growth inhibition by higher sulfate concentrations was overcome by the addition of O-acetylserine, which is known as derepressor of sulfate-assimilating enzymes, and by reduced glutathione. All enzymes of the sulfate assimilation pathway. ATP-sulfurylase, adenylylphosphate-sulfotransferase, thiosulfonate reductase and O-acetylserine sulfhydrylase are present in R. globiformis. Sulfate was taken up by the cells and the sulfur incorporated into the amino acids cysteine, methionine and homocysteine. It is concluded, that the failure of R. globiformis to grow on higher concentrations of sulfate is caused by disregulation of the sulfate assimilation pathway. Some preliminary evidence for this view is given in comparing the activities of some of the involved enzymes after growth on different sulfur sources and by examining the effect of O-acetylserine on these activities.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-072X
    Keywords: Phototrophic purple bacteria ; Ectothiorhodospira ; Fatty acid composition ; Salt adaptation ; Membrane fluidity ; Bilayer stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Influences of the salt concentration on the fatty acid composition of Ectothiorhodospira species and other phototrophic purple bacteria have been analysed. Major fatty acids in bacteria of the genera Rhodobacter, Rhodopseudomonas, Chromatium, and Ectothiorhodospira were straight chain saturated and monounsaturated C-16 and C-18 fatty acids. Salt-dependent responses of all investigated bacteria revealed relations to their salt optima. Minimum values of C-16 and saturated fatty acids and maximum values of C-18 and unsaturated fatty acids were found at or close to the salt optima. Responses of Ectothiorhodospira mobilis upon changes in salinity were nearly identical, whether cells were grown in batch culture or in continuous culture with identical dilution rates at all salt concentrations. With increasing temperature, the fatty acid composition of Ectothiorhodospira mobilis and Ectothiorhodospira halophila strains showed decreasing portions of C-18 and of unsaturated fatty acids, while the contents of C-16 and saturated fatty acids increased. The results are discussed with respect to bilayer stabilisation and membrane fluidity.
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  • 3
    ISSN: 1432-072X
    Keywords: Ectothiorhodospira ; Phospholipids ; Salt adaptation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Major components of polar lipids of halophilic phototrophic Ectothiorhodospira species were PG, CL, PC and PE. PA was only present in minor amounts. According to 14C-incorporation, polar lipids approximated to 75%–93% of the total lipid carbon. With increasing salinity, a strong increase in the portion of PG and a decrease in that of PE (especially in Ectothiorhodospira mobilis BN 9903) and CL (especially in E. halophila strains) were observed. Moreover, there was a significant increase in the excess negative charges of phospholipids upon increasing medium salinity. This increase was most dramatic in the slightly halophilic E. mobilis BN 9903, but quantitatively less important in both strains of E. halophila which had, however, a higher percentage of negative charges of their lipids. During salt-shift experiments, E. halophila BN 9630 responded to suddenly increased salinity by promoting the biosynthesis of PG and decreasing that of PC, CL and PE. Upon dilution stress, responses were reversed and resulted in a strong increase in PE biosynthesis. The effects of lipid charges and bilayer forming forces in stabilizing the membranes of Ectothiorhodospira species during salt stress are discussed.
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  • 4
    Publication Date: 2019-02-01
    Description: Rhodopila globiformis: is the most acidophilic anaerobic anoxygenic phototrophic purple bacterium and was isolated from a warm acidic sulfur spring in Yellowstone Park. Its genome is larger than genomes of other phototrophic purple bacteria, containing 7248 Mb with a G + C content of 67.1% and 6749 protein coding and 53 RNA genes. The genome revealed some previously unknown properties such as the presence of two sets of structural genes pufLMC for the photosynthetic reaction center genes and two types of nitrogenases (Mo-Fe and V-Fe nitrogenase), capabilities of autotrophic carbon dioxide fixation and denitrification using nitrite. Rhodopila globiformis assimilates sulfate and utilizes the C1 carbon substrates CO and methanol and a number of organic compounds, in particular, sugars and aromatic compounds. It is among the few purple bacteria containing a large number of pyrroloquinoline quinone-dependent dehydrogenases. It has extended capacities to resist stress by heavy metals, demonstrates different resistance mechanisms to antibiotics, and employs several toxin/antitoxin systems.
    Type: Article , PeerReviewed
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  • 5
    Publication Date: 2019-02-01
    Description: A new cyclic hexapeptide, cyclo-(Gly-Leu-Val-IIe-Ala-Phe), named bacicyclin (1), was isolated from a marine Bacillus sp. strain associated with Mytilus edulis. The sequences of the amino acid building blocks of the cyclic peptide and its structure were determined by 1D- and 2D-NMR techniques. Marfey's analysis showed that the amino acid building blocks had L-configuration in all cases except for alanine and phenylalanine, which had D-configuration. Bacicyclin (1) exhibited antibacterial activity against the clinically relevant strains Enterococcus faecalis and Staphylococcus aureus with minimal inhibitory concentration values of 8 and 12 μM, respectively. These results demonstrate the potential of marine bacteria as a promising source for the discovery of new antibiotics.
    Type: Article , PeerReviewed
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  • 6
    Publication Date: 2019-02-01
    Description: Pseudovibrio is a marine bacterial genus members of which are predominantly isolated from sessile marine animals, and particularly sponges. It has been hypothesized that Pseudovibrio spp. form mutualistic relationships with their hosts. Here, we studied Pseudovibrio phylogeny and genetic adaptations that may play a role in host colonization by comparative genomics of 31 Pseudovibrio strains, including 25 sponge isolates. All genomes were highly similar in terms of encoded core metabolic pathways, albeit with substantial differences in overall gene content. Based on gene composition, Pseudovibrio spp. clustered by geographic region, indicating geographic speciation. Furthermore, the fact that isolates from the Mediterranean Sea clustered by sponge species suggested host-specific adaptation or colonization. Genome analyses suggest that Pseudovibrio hongkongensis UST20140214-015BT is only distantly related to other Pseudovibrio spp., thereby challenging its status as typical Pseudovibrio member. All Pseudovibrio genomes were found to encode numerous proteins with SEL1 and tetratricopeptide repeats, which have been suggested to play a role in host colonization. For evasion of the host immune system, Pseudovibrio spp. may depend on type III, IV, and VI secretion systems that can inject effector molecules into eukaryotic cells. Furthermore, Pseudovibrio genomes carry on average seven secondary metabolite biosynthesis clusters, reinforcing the role of Pseudovibrio spp. as potential producers of novel bioactive compounds. Tropodithietic acid, bacteriocin, and terpene biosynthesis clusters were highly conserved within the genus, suggesting an essential role in survival, for example through growth inhibition of bacterial competitors. Taken together, these results support the hypothesis that Pseudovibrio spp. have mutualistic relations with sponges.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
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    Format: archive
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  • 7
    Publication Date: 2019-02-01
    Description: The structural repertoire of bioactive naphthacene quinones is expanded by engineering Streptomyces albus to express the lysolipin minimal polyketide synthase II (PKS II) genes from Streptomyces tendae Tü 4042 (llpD-F) with the corresponding cyclase genes llpCI-CIII. Fermentation of the recombinant strain revealed the two new polyaromatic tridecaketides lysoquinone-TH1 (7, identified) and TH2 (8, postulated structure) as engineered congeners of the dodecaketide lysolipin (1). The chemical structure of 7, a benzo[a]naphthacene-8,13-dione, was elucidated by NMR and HR-MS and confirmed by feeding experiments with [1,2-13C2]-labeled acetate. Lysoquinone-TH1 (7) is a pentangular polyphenol and one example of such rare extended polyaromatic systems of the benz[a]napthacene quinone type produced by the expression of a minimal PKS II in combination with cyclases in an artificial system. While the natural product lysolipin (1) has antimicrobial activity in nM-range, lysoquinone-TH1 (7) showed only minor potency as inhibitor of Gram-positive microorganisms. The bioactivity profiling of lysoquinone-TH1 (7) revealed inhibitory activity towards phosphodiesterase 4 (PDE4), an important target for the treatment in human health like asthma or chronic obstructive pulmonary disease (COPD). These results underline the availability of pentangular polyphenolic structural skeletons from biosynthetic engineering in the search of new chemical entities in drug discovery
    Type: Article , PeerReviewed
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  • 8
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    IFM-GEOMAR
    In:  In: IFM-GEOMAR [Annual] Report 2002-2004 From the Seafloor to the Atmosphere - Marine Sciences at IFM-GEOMAR Kiel -. , ed. by Villwock, A. IFM-GEOMAR, Kiel, Germany, pp. 44-46.
    Publication Date: 2019-03-08
    Type: Book chapter , NonPeerReviewed
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  • 9
    Publication Date: 2019-04-17
    Description: Isolierung, Charakterisierung und Produktion antimikrobieller Peptide (AMPs) aus marinen Mikroorganismen
    Type: Report , NonPeerReviewed
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  • 10
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    Institut für Meereskunde an der Universität Kiel
    In:  Institut für Meereskunde an der Universität Kiel, Kiel, Germany, 16 pp.
    Publication Date: 2019-04-18
    Type: Report , NonPeerReviewed
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