Bioassay experiments were performed two times (with 2years in between) in order to investigate if nitrogen (N, ammonium), phosphorus (P, phosphate) and carbon (C, glucose) additions would stimulate ...the growth of bacteria and phytoplankton differently in three different tropical aquatic environments. The water and their indigenous microbial communities were taken from a freshwater coastal lake (Cabiunas), a coastal (Anjos), and an offshore marine station (Sonar) in the Atlantic outside Cabo Frio, Rio de Janeiro State, Brazil. Ammonium, phosphate and glucose were added alone or in combination to triplicate bottles. In the lake, P seemed to be the primary limiting factor during the first experiment, since both bacterial production and phytoplankton growth was stimulated by the P addition. Two years later, however, addition of P inhibited phytoplankton growth. During both years, C was closely co-limiting for bacteria since CP additions increased the response considerably. For both the coastal and offshore seawater stations, phytoplankton growth was clearly stimulated by N addition in both years and the bacteria responded either to the P, N or C additions (alone or in combination). To conclude, the results from these tropical aquatic systems show that it is possible that phytoplankton and bacteria may compete for a common resource (P) in lakes, but can be limited by different inorganic nutrients in marine waters as well as lakes, suggesting that phytoplankton and bacteria do not necessarily compete for the same growth limiting nutrient in these environments.
► Phytoplankton and bacterial nutrient limitation was investigated in tropical waters. ► Phytoplankton and bacteria may compete for a common resource (P) in a tropical lake. ► Phytoplankton and bacteria can be limited by different nutrients in marine waters. ► Phytoplankton and bacteria do not necessarily compete for the same nutrient.
The aim of this work was to develop the composition of a medium for the cultivation of six microbial strains forming a deodorizing consortium: Pseudomonas fluorescens, Enterococcus faecium, Bacillus ...subtilis, Bacillus megaterium, Leuconostoc mesenteroides and Lactobacillus plantarum. The study focused on the optimization of a highly efficient culture medium composed of readily available components of plant origin to maximize microbial biomass yields, and to create a less expensive alternative to the commercial Tryptic Soy Broth medium (TSB). After preliminary efficiency screening of all tested media components, we selected four substrates for further optimization-soy protein concentrate (SPC), glucose or sucrose, and phosphate salts. The final concentrations of all components were fine-tuned using the Taguchi design for experiments according to an L9 array. Taguchi optimization led to formulation of a culture medium, which was approximately 5 times cheaper than TSB (depending on the components used). Consequently, microbial biomass yields were improved by up to 15-fold (1564%), depending on the strain. The results obtained in the laboratory experiments were then confirmed in pilot- (42 L) and industrial- (300 L) scale fermentation. Our results show that this method of using a parallel culture microbioreactor with the Taguchi approach can be recommended for optimization of culture media based on substrates of plant origin.
The Baltic Sea is prone to oxygen deficiency due to the restricted water exchange with the North Sea in coincidence with a high biological oxygen demand. The partitioning of organic carbon between ...respiration, accumulation and export is co-determined by phytoplankton primary production and its subsequent bacterial remineralization. Here, we investigated net phytoplankton primary production, heterotrophic bacterial biomass production and dark CO2 fixation by on-board incubations with radiolabeled tracers in the Baltic Proper and in the Gulf of Riga after the main spring bloom. Results show that low phytoplankton standing stocks of ≤1.6 µg chlorphyll a L-1 sustained net primary production of 161-724 mg C m-2 d-1 under nitrogen limitation. Estimates of bacterial carbon remineralization suggest that freshly produced organic carbon was supplied to the aphotic zone at all stations. In the southern Baltic Proper, net primary production exceeded the bacterial carbon demand in the upper mixed layer, suggesting that organic matter derived from nutrient-limited primary production was available for export to bacterial communities below the oxycline. On average, 46% of heterotrophic bacterial production was mediated in oxygen minimum zones, revealing the high importance of organic matter recycling under hypoxic and anoxic conditions for the carbon budget. Dark CO2 fixation of up to 4.33 µg C L-1 d-1 in sulfide-free waters equaled 9-54% of the co-inciding heterotrophic bacterial carbon demand and may have provided another organic carbon source for heterotrophic activity. Substantially higher dark CO2 fixation up to 25.46 µg C L-1 d-1 was determined in sulfidic waters. Since our study was conducted five months after the major Baltic inflow event in winter 2014/2015, potential effects of deep water ventilation could be investigated. In the Gotland Basin, heterotrophic bacterial production in renewed oxygen-rich bottom water was similar to that in the uplifted oxygen-deficient former bottom water, while it was significantly reduced in sulfidic waters. Hence, our results suggest that the removal of hydrogen sufide by inflow events has a high potential to increase bacterial carbon remineralization.
Bacterial abundance and assimilation of 3H-leucine were examined using a combination of microautoradiography and fluorescent in situ hybridization (Micro-FISH) to determine the bacterioplankton ...community structure and estimate the contribution of major bacterial groups to total bacterial biomass production (leucine incorporation) from the Pearl River mouth to the open water area in the South China Sea. Alpha-, beta-, gamma-proteobacteria and the Cytophaga- Flavobacterium cluster differed substantially in their relative abundance and contribution to leucine assimilation along the salinity gradient. The contribution of major bacterial groups to leucine assimilation was closely associated with their relative abundance in the communities. Alpha- proteobacteria were the dominant group in the high-salinity water in terms of abundance and 3H-leucine assimilation, whereas beta-proteobacteria were more important in fresh water. At all stations, gamma-proteobacteria were a minor component, but the Cytophaga-Flavobacterium cluster was always a significant component in both marine and freshwater systems. The relative abundance of bacterial groups explained the variation in 3H-leucine assimilation by the major bacterial groups to a great extent. At the singlebacterial group level, a statistically significant correlation between abundance and leucine- uptake activity was observed for beta-proteobacteria, suggesting that the relative abundance of betaproteobacteria in bacterioplankton communities was controlled by growth-related processes. In general, the numerical dominance of the major phylogenetic groups and their contribution to total bacterial biomass production varied consistently along the salinity gradient in the South China Sea.
This study investigates the turnover of polysaccharides by heterotrophic bacterioplankton in the northern Bay of Biscay, a productive marine system on the continental margin of the temperate Atlantic ...Ocean. Bacterial biomass production (BBP) near the surface ranged from 0.5 to 25.7 nmol C L−1 h−1 during small phytoplankton blooms in May and June that occurred after the main spring bloom. A direct relationship between BBP and total polysaccharides strongly suggests the dependence of bacterial growth on the availability of semi-labile organic matter. Concentrations of combined glucose as well as rate constants of extracellular glucosidase activity and glucose uptake were determined to estimate the actual carbon fluxes from bacterial polysaccharide turnover. Results reveal that the degradation of polysaccharides in the upper 100 m of the water column sustained a glucose flux of 15.2-32.3 mg C m−2 d−1 that was available for bacterial consumption. The mean turnover time for polysaccharides was 170 and 165 days for α- and β-glycosidic linked polymers, respectively. Incorporation of free glucose supported 0.4-19.6% of BBP. The availability of nitrate plus nitrite (NO
x
) was identified as one factor increasing bacterial incorporation of glucose in most samples. Our results demonstrate that the bacterial recycling of polysaccharides generated a significant flux of organic carbon in microbial food-webs and biogeochemical processes.
In this project we studied the microbiological quality of soft pipeline deposits removed from drinking water distribution networks during mechanical cleaning. Drinking water and deposit samples were ...collected from 16 drinking water distribution networks located at eight towns in different parts of Finland. Soft pipeline deposits were found to be the key site for microbial growth in the distribution networks. The microbial numbers in the soft deposits were significantly higher than numbers in running water. The highest microbial numbers were detected in the main deposit pushed ahead by the first swab. The deposits contained high numbers of heterotrophic bacteria, actinomycetes and fungi. Also coliform bacteria were often isolated from deposit samples. Manganese and copper in the deposits correlated negatively with the numbers of heterotrophic bacteria. After a year, the viable microbial numbers in the new deposits were almost as high as in the old deposits before the first mechanical cleaning. The bacterial biomass production was higher in the new than in the old deposits.
Bacterial abundance and assimilation of H-3-leucine were examined using a combination of microautoradiography and fluorescent in situ hybridization (Micro-FISH) to determine the bacterioplankton ...community structure and estimate the contribution of major bacterial groups to total bacterial biomass production (leucine incorporation) from the Pearl River mouth to the open water area in the South China Sea. Alpha-, beta-, gamma-proteobacteria and the Cytophaga-Flavobacterium cluster differed substantially in their relative abundance and contribution to leucine assimilation along the salinity gradient. The contribution of major bacterial groups to leucine assimilation was closely associated with their relative abundance in the communities. Alpha-proteobacteria were the dominant group in the high-salinity water in terms of abundance and H-3-leucine assimilation, whereas beta-proteobacteria were more important in fresh water. At all stations, gamma-proteobacteria were a minor component, but the Cytophaga-Flavobacterium cluster was always a significant component in both marine and freshwater systems. The relative abundance of bacterial groups explained the variation in 3H-leucine assimilation by the major bacterial groups to a great extent. At the singlebacterial group level, a statistically significant correlation between abundance and leucine-uptake activity was observed for beta-proteobacteria, suggesting that the relative abundance of betaproteobacteria in bacterioplankton communities was controlled by growth-related processes. In general, the numerical dominance of the major phylogenetic groups and their contribution to total bacterial biomass production varied consistently along the salinity gradient in the South China Sea.
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