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  • 1
    Digitale Medien
    Digitale Medien
    Bacterial induction and inhibition of a fast mecrotic response in Gracilaria conferta (Rhodophyta) (1997)
    Springer
    Journal of applied phycology 9 (1997), S. 277-285 
    Details
    ISSN: 1573-5176
    Schlagwort(e): cefotaxim ; epiphytic bacteria ; Gracilaria ; seaweed-microbe interactions ; seaweed pathology ; Vancomycin
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Of 45 bacterial isolates from healthy tips of Gracilaria conferta (Schousboe ex Montagne) J. et G. Feldmann, 29% were identified as ‘conditional inducers’ of an apical necrosis. That is, the isolates induced necrotic tips in G. conferta within 16 h after elimination of most of the resident microflora from the alga. Several disinfectants and antibiotics were screened for their ability to induce algal susceptibility to the bacteria and to suppress uncontrolled appearance of tip necrosis. Treatment with 100 mg L-1 Cefotaxim + 100 mg L-1Vancomycin over three days was the least damaging and most efficient. Tip necrosis was related to isolates of the Corynebacterium-Arthrobacter-group and to the Flavobacterium-Cytophaga-group. The damaging effect occurred due to the bacterial excretion of active agents and was not correlated with acapability to degrade agar. The damaging influence of four Cytophaga-likestrains was inhibited by 20 of 40 isolates. This protective effect was caused by very different organisms. In five of six cases examined further, the effect was not cellbound, but due to the excretion of agents. These were not antimicrobially active, but inactivated necrosis-inducing excretions. These results indicate that epiphytic bacterial degradation or inactivation of damaging agents is a protecting factor in Gracilaria, which prevents the alga from being harmed by epiphytes.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1007990712925
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  • 2
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    Evidence for dependency of bacterial growth on enzymatic hydrolysis of particulate organic matter in the mesopelagic ocean (1993)
    Inter Research
    In:  Marine Ecology Progress Series, 93 . pp. 277-283.
    Details
    Publikationsdatum: 2018-03-05
    Beschreibung: Organic material entering the oceanic mesopelagic zone may either reenter the euphotic zone or settle into deeper waters. Therefore it is important to know about mechanisms and efficiency of substrate conversion in this water layer. Bacterial biomass, bacteria secondary production (BSP). extra­cellular peptidase activity (EPA) and particulate organic nitrogen (PON) were measured in vertical pro­files of the North Atlantic (46° N 18° W; 57° N 23° W) during the Joint Global Ocean Flux Study (JGOFS) cruise in May 1989. The magnitude of these parameters decreased differently with depth. The strong­est decreases were observed for bacterial production (3H-thymidine incorporation) and peptide turn­over (using the substrate analog leucine-methylcoumarinylamide). Bacterial biomass and peptidase potential activity were not reduced as much in the mesopelagic zone. Peptidase potential per unit cell biomass of mesopelagic bacteria was 2 to 3 times higher than that of bacteria in surface water. Nevertheless bacterial growth at depth was slow, due to slow actual hydrolysis. Values of theoretical PON hydrolysis were calculated from PON measurements and protein hydrolysis rates. These corre­sponded well to bacterial production rates, and the degree of correspondence increased from a factor of 0.63 (PON hydrolysis/ESP) in the mixed surface layer to 0.87 in the mesopelagic zone. Thus we hypothesized an effective coupling between particle hydrolysis and uptake of hydrolysate by bacteria, which depletes the deeper water of easily degradable substrates as hydrolysates usually are. The low enzymatic PON turnover rate of 0.04 d- 1 in the subeuphotic zone suggests that residence time of parti­cles within a depth stratum may be important for its contribution to export. storage and recycling of organic matter.
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  • 3
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    Bacterial induction and inhibition of a fast necrotic response in Gracilaria conferta (Rhodophyta) (1997)
    Springer
    In:  Journal of Applied Phycology, 9 (3). pp. 277-285.
    Details
    Publikationsdatum: 2018-06-01
    Beschreibung: Of 45 bacterial isolates from healthy tips of Gracilaria conferta (Schousboe ex Montagne) J. et G. Feldmann, 29% were identified as 'conditional inducers' of an apical necrosis. That is, the isolates induced necrotic tips in G. conferta within 16 h after elimination of most of the resident microflora from the alga. Several disinfectants and antibiotics were screened for their ability to induce algal susceptibility to the bacteria and to suppress uncontrolled appearance of tip necrosis. Treatment with 100 mg L-1 Cefotaxim + 100 mg L-1 Vancomycin over three days was the least damaging and most efficient. Tip necrosis was related to isolates of the Corynebacterium-Arthrobacter-group and to the Flavobacterium-Cytophaga-group. The damaging effect occurred due to the bacterial excretion of active agents and was not correlated with a capability to degrade agar. The damaging influence of four Cytophaga-like strains was inhibited by 20 of 40 isolates. This protective effect was caused by very different organisms. In five of six cases examined further, the effect was not cellbound, but due to the excretion of agents. These were not antimicrobially active, but inactivated necrosis-inducing excretions. These results indicate that epiphytic bacterial degradation or inactivation of damaging agents is a protecting factor in Gracilaria, which prevents the alga from being harmed by epiphytes.
    Materialart: Article , PeerReviewed
    Format: text
    DOI: 10.1023/A:1007990712925
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  • 4
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    Changing bacterioplankton growth characteristics on a large spatial scale: oligotroph versus mesotrophic ocean (2006)
    Inter Research
    In:  Marine Ecology Progress Series, 323 . pp. 21-33.
    Details
    Publikationsdatum: 2018-06-01
    Beschreibung: This study deals with large spatial scale differences in the ratios between bacterial leucine incorporation (TLi: protein synthesis) and thymidine incorporation (TTi: DNA synthesis) in oligotrophic offshore and comparatively more mesotrophic inshore (sub)tropical regions of the Atlantic Ocean. Observations were derived from 2 RV ‘Polarstern’ cruises, one of which traversed a meridional mid-ocean transect while the other followed the African coast line. Average values (from 42°N to 35°S) of TLi, TTi and chlorophyll a (chl a) concentration were 40.3 pmol leucine l–1 h–1, 1.32 pmol thymidine l–1 h–1 and 0.18 µg chl a l–1 along the offshore transect, compared to 51.8 pmol leucine l–1 h–1, 2.72 pmol thymidine l–1 h–1 and 0.29 µg chl a l–1 along the inshore transect. Mean values of the TLi:TTi ratio (which defines bacterial growth characteristics) were 32.4 in offshore waters and 20.5 in inshore waters. Offshore ratios of TLi:chl a or TTi:chl a (proxy for bacterial substrate) were 274.1 and 8.5, compared to inshore ratios of 198.7 and 10.0, respectively. This means that, per unit of chl a, considerably higher bacterial protein synthesis was supported in water farther from the coast than near the coast, whereas bacterial DNA synthesis per unit chl a was slightly higher in the latter. Because temperature variability along the cruise tracts was rather similar (except in the Benguela upwelling region), we assume that substrate supply was mainly responsible for the observed significant differences in bacterial growth characteristics. In addition, the potential different contributions of picocyanobacteria to leucine uptake (TLi) must be considered. We conclude that the different TLi:TTi ratios in (sub)tropical offshore and inshore waters reflect reactions of the relevant bacterial communities to prevailing environmental conditions. Therefore, we did not interpret our results in the context of the currently used terms ‘balanced’ or ‘unbalanced’ growth. Bacterial community growth may be balanced in both regions of study, but at different levels of the TLi:TTi ratio.
    Materialart: Article , PeerReviewed
    Format: text
    DOI: 10.3354/meps323021
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  • 5
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    Is the CTC dye technique an adequate approach for estimating active bacterial cells? (1999)
    Inter Research
    In:  Aquatic Microbial Ecology, 17 (2). pp. 207-209.
    Details
    Publikationsdatum: 2016-05-26
    Materialart: Article , PeerReviewed
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  • 6
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    Response of aquatic bacterial populations to substrate enrichment (1994)
    Inter Research
    In:  Marine Ecology Progress Series, 104 . pp. 173-184.
    Details
    Publikationsdatum: 2019-03-15
    Beschreibung: The responses of natural bacterial populations in the waters of the Kiel Fjord, Germany, and in Lake Kinneret, Israel, to additions of organic substrates were followed by determining changes over 24 h either in direct cell counts or in 3H-thymidine incorporation, and in the Kiel Fjord additionally in 3H-leucine incorporation. In parallel, 1 ym filtered water samples were stored for 3 or 4 d in order to starve the indigenous bacterial populations prior to repeating the substrate addition experiments. Generally, upon substrate addition, relatively higher incorporation of radiotracers was noted in the preincubated samples. Growth response to substrate addition even in starved populations was only significant after 24 h. Incorporation rates of 3H-thymidine and 3H-leucine were more sensitive indicators of bacterial response to substrate additions than cell counts. Continued cell replication in unsupplemented controls, and insignificant increase over time of radiotracer incorporation in most of the fresh samples with added supplements, indicated that the indigenous bacterial populations in Kiel Fjord and Kinneret were apparently not substrate limited. Comparison of actual bacterial production after 24 h (direct counts) to that predicted by 3H-thymidine incorporation after 1 h showed that although reasonably good predictions of daily production were obtained in the unsupplemented samples, this was usually not the case when substrates were added.
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  • 7
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    Species-Specific Bacterial Communities in the Phycosphere of Microalgae? (2007)
    Springer
    In:  Microbial Ecology, 53 (4). pp. 683-699.
    Details
    Publikationsdatum: 2017-03-22
    Beschreibung: Specific associations of bacteria with phytoplankton have recently been reported in the literature. In our study, we analyzed bacterial communities of microalgal cultures related to algal growth phases. Seven freshly isolated key diatom and dinoflagellate species from Helgoland Roads, North Sea, were investigated. The community composition of associated bacteria as well as the cell numbers, the photosynthetic efficiency of the algae, and the depletion of inorganic nutrients in the medium were recorded over a period of 8 weeks in batch cultures. Diversity and succession of bacterial communities was analyzed by ribosomal intergenic spacer analysis. Phylogenetic analysis of bacterial populations was performed by denaturing gradient gel electrophoresis of 16S rRNA genes followed by DNA sequence analysis. Members of Alphaproteobacteria and Gammaproteobacteria and the Flavobacteria–Sphingobacteria group within the Bacteroidetes phylum predominated in the cultures. Differences in free-living and attached bacterial populations were observed between the phylogenetic groups. Shifts in the bacterial communities could not be correlated to changes of nutrient levels or algal growth phases. Regarding our results, it should not be generalized that the compositions of the bacterial communities are strictly species specific for microalgae. The importance of factors like the composition of exudates is apparent.
    Materialart: Article , PeerReviewed
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    DOI: 10.1007/s00248-006-9162-5
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  • 8
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    Phosphatase activity in the sea (2003)
    Springer
    In:  Hydrobiologia, 493 . pp. 187-200.
    Details
    Publikationsdatum: 2018-07-02
    Beschreibung: Phosphatase is a key-enzyme in the marine environment, although life in the sea is normally not P limited. Expression of phosphatase in algae is generally regulated by the prevailing external concentration of inorganic phosphate, but the internal N:P ratio may also play a role. For bacteria, additional mechanisms like their C and N demands may be important. This is suggested by high phosphatase activities occasionally measured in eutrophic or deep water in the presence of relatively high phosphate concentrations. The distribution of phosphatase activity among the particulate and the dissolved fractions is highly variable. In particular, the dissolved fraction can contribute considerably to the total phosphatase activity (up to 70%), which differs from the pattern of other hydrolytic ectoenzymes. Parts of this fraction may originate from marine protozoa. The contribution of bacteria and phytoplankton to the particle-associated fraction of phosphatase is extremely variable, depending on P-availability, the dominant organisms, water depth and environmental factors. Community analysis revealed that bacteria attached to marine snow and N2-fixing cyanobacteria were frequently strong producers of phosphatase. Field studies carried out on a great variety of marine regions suggest that phosphatase activity is generally a good indicator of the P status of phytoplankton. Several heat-stable or heat-labile phosphatases, isolated from marine organisms living in extreme or other environments have been recommended for biotechnological applications.
    Materialart: Article , PeerReviewed
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    DOI: 10.1023/A:1025453918247
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  • 9
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    Profiles of ectoenzymes in the Indian Ocean: Phenomena of phosphatase activity in the mesopelagic zone (1999)
    Inter Research
    In:  Aquatic Microbial Ecology, 19 . pp. 139-148.
    Details
    Publikationsdatum: 2016-05-26
    Beschreibung: Phosphatase (P-ase) activity was determined together with other extracellular enzyme activities, bacterial abundance and production rates during the 2 SW Monsoon process studies of the German JGOFS Arabian Sea Program. Water samples were collected along the cruise tracks from the equator to the upwelling region at the shelf edge off Oman. Depth profiles of P-ase activity were strikingly different from those of the other enzymes. While values of aminopeptidase and β-glucosidase generally decreased below the euphotic zone, P-ase increased by factors of 1 to 7. The relation between peptidase- and P-ase activity was from 4 to 21 at the surface and from 3 to 5 at 800 m depth. Because P-ase production (dissolved and cell-bound) in deep waters is mainly dependent on bacteria, P-ase activities per bacterial cell were calculated: these were, on average, 37 times higher at 800 m than at the surface. We also observed a positive correlation of P-ase activity with phosphate concentrations in the depth profiles below the euphotic zone, while this relationship was much more variable in the mixed surface layer. These observations suggest that C-limited bacteria in the deep strata did not primarily focus on the phosphate generated by their P-ase activity but on the organic C compounds which were simultaneously produced and which could probably not be taken up prior to the hydrolytic detachment of phosphate. It is hypothesised that a considerable part of the measured P-ase activity was dissolved (though it might have originated from bacteria). These enzymes may be important for the slow, but steady regeneration of phosphate and organic C in mesopelagic waters.
    Materialart: Article , PeerReviewed
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    DOI: 10.3354/ame019139
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  • 10
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    Climate warming in winter affects the coupling between phytoplankton and bacteria during the spring bloom: a mesocosm study (2008)
    Inter Research
    In:  Aquatic Microbial Ecology, 51 . pp. 105-115.
    Details
    Publikationsdatum: 2019-09-23
    Beschreibung: The response of the phytoplankton and bacterial spring succession to the predicted warming of sea surface temperature in temperate climate zones during winter was studied using an indoor-mesocosm approach. The mesocosms were filled with winter water from the Kiel Fjord, Baltic Sea. Two of them were started at ~2°C and the temperature was subsequently increased according to the decadal temperature profile of the fjord (ΔT 0°C, baseline treatment). The other mesocosms were run at 3 elevated temperatures with differences of ΔT +2, +4 and +6°C. All mesocosms were exposed to the same light conditions. Timing of peak phytoplankton primary production (PP) during the experimental spring bloom was not significantly influenced by increasing temperatures, whereas the peak of bacterial secondary production (BSP) was accelerated by about 2 d per °C. This suggests that, in case of warming, the spring peak of bacterial degradation of organic matter (in terms of BSP) would occur earlier in the year. Furthermore, the lag time between the peaks of PP and BSP (about 16 d for ΔT 0°C) would diminish progressively at elevated temperatures. The average ratio between BSP and PP increased significantly from 0.37 in the coldest mesocosms to 0.63 in the warmest ones. Community respiration and the contribution of picoplankton (〈3 µm fraction) to this also increased at elevated temperatures. Our results lead to the prediction that climate warming during the winter/ early spring in temperate climate zones will favor bacterial degradation of organic matter by tightening the coupling between phytoplankton and bacteria. However, if PP is reduced by warming, as in our experiments, this will not necessarily lead to increased recycling of organic matter (and CO2).
    Materialart: Article , PeerReviewed
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    DOI: 10.3354/ame01198
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