Theoretical and empirical conversion factors for determining bacterial production in freshwater sediments via leucine incorporation

Buesing, Nanna; Marxsen, Jürgen

doi:10.4319/lom.2005.3.101

Cited by 45 publications

(33 citation statements)

References 29 publications

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“…It has been reported that differences in leucinebased estimates of BP may be driven in part by variation in the in the efficiency with which leucine is converted into bacterial biomass and that the use of a constant leucine-to-CCF may inaccurately represent in situ rates of BP and BGE (Kirchman, 1993;Buesing and Marxsen, 2005;Alonso-Sáez et al, 2007). Although the influence of variability in CCF may be most pronounced in oligotrophic waters (Alonso-Sáez et al, 2007), this phenomenon may be applicable to any range of systems differing in productivity or degree of resource enrichment.…”

Section: Discussionmentioning

confidence: 99%

Organic substrate quality as the link between bacterioplankton carbon demand and growth efficiency in a temperate salt-marsh estuary

Apple

Giorgio

2007

ISME J

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Bacterioplankton communities play a key role in aquatic carbon cycling, specifically with respect to the magnitude of organic carbon processed and partitioning of this carbon into biomass and respiratory losses. Studies of bacterioplankton carbon demand (BCD) and growth efficiency (BGE) frequently report higher values in more productive systems, suggesting these aspects of carbon metabolism may be positively coupled. However, the existence of such a relationship in natural aquatic systems has yet to be identified. Using a comprehensive 2-year study of bacterioplankton carbon metabolism in a temperate estuary, we investigated BCD and BGE and explored factors that may modulate their magnitude and coherence, including nutrient concentrations, dissolved nutrient uptake and source and quality of dissolved organic carbon (DOC). During the course of our study, BCD ranged from 0.4 to 15.9 lg l À1 h -1, with an overall mean of 3.8 lg l À1 h -1. Mean BGE was similar to that reported for other estuarine systems (0.32) and of comparable range (that is, 0.06-0.68). Initial analyses identified a negative correlation between BCD and BGE, yet removal of the effect of temperature revealed an underlying positive coupling that was also correlated with long-term DOC lability. Whereas BCD was weakly related to ambient DOC concentrations, neither BCD nor BGE showed any relationship with ambient nutrient concentrations or nutrient uptake stoichiometries. We conclude that in this carbon-rich estuary, organic matter source and quality play an important role in regulating the magnitude of carbon metabolism and may be more important than nutrient availability alone in the regulation of BGE.

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Section: Discussionmentioning

confidence: 99%

Organic substrate quality as the link between bacterioplankton carbon demand and growth efficiency in a temperate salt-marsh estuary

Apple

Giorgio

2007

ISME J

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“…Cell production, in turn, was calculated from biomass production of prokaryotes (i.e., [ 3 H]leucine incorporation), assuming that 1 m 3 of prokaryotic biomass equaled 7.8 fg of C and that the volume of the average cell in water samples was 0.02 m 3 (8). Biomass production was calculated from leucine incorporation rates using a conversion factor established for freshwater sediment bacteria (12). Isotope dilution has been found to be minor (1.17) (10) and was therefore not taken into account.…”

Section: Methodsmentioning

confidence: 99%

Infection Paradox: High Abundance but Low Impact of Freshwater Benthic Viruses

Filippini

Buesing

Bettarel

et al. 2006

Appl Environ Microbiol

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104

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The discovery of an abundant and diverse virus community in oceans and lakes has profoundly reshaped ideas about global carbon and nutrient fluxes, food web dynamics, and maintenance of microbial biodiversity. These roles are exerted through massive viral impact on the population dynamics of heterotrophic bacterioplankton and primary producers. We took advantage of a shallow wetland system with contrasting microhabitats in close proximity to demonstrate that in marked contrast to pelagic systems, viral infection, determined directly by transmission electron microscopy, and consequently mortality of prokaryotes were surprisingly low in benthic habitats in all seasons. This was true even though free viruses were abundant throughout the year and bacterial infection and mortality rates were high in surrounding water. The habitats in which we found this pattern include sediment, decomposing plant litter, and biofilms on aquatic vegetation. Overall, we detected viruses in only 4 of a total of ϳ15,000 bacterial cells inspected in these three habitats; for comparison, nearly 300 of ϳ5,000 cells suspended in the water column were infected. The strikingly low incidence of impact of phages in the benthos may have important implications, since a major portion of microbial biodiversity and global carbon and nutrient turnover are associated with surfaces. Therefore, if failure to infect benthic bacteria is a widespread phenomenon, then the global role of viruses in controlling microbial diversity, food web dynamics, and biogeochemical cycles would be greatly diminished compared to predictions based on data from planktonic environments.

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“…Fungal biomass, growth rate, and production were estimated by determining ergosterol concentrations and rates of [ 14 C]acetate incorporation into ergosterol (28). Samples were incubated for 5 h at ambient lake temperatures in 4 ml of filtered lake water containing sodium [ 14 C]acetate (Amersham, Little Chalfont, Buckinghamshire, United Kingdom); the specific activity of added acetate was 3.7 10 7 Bq mmol Ϫ1 (27). The total added acetate concentration was 5 mM.…”

Section: Vol 72 2006 Benthic Microbial Productivity 597mentioning

confidence: 99%

Benthic Bacterial and Fungal Productivity and Carbon Turnover in a Freshwater Marsh

Buesing

Gessner

2006

Appl Environ Microbiol

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109

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Heterotrophic bacteria and fungi are widely recognized as crucial mediators of carbon, nutrient, and energy flow in ecosystems, yet information on their total annual production in benthic habitats is lacking. To assess the significance of annual microbial production in a structurally complex system, we measured production rates of bacteria and fungi over an annual cycle in four aerobic habitats of a littoral freshwater marsh. Production rates of fungi in plant litter were substantial (0.2 to 2.4 mg C g ؊1 C) but were clearly outweighed by those of bacteria (2.6 to 18.8 mg C g ؊1 C) throughout the year. This indicates that bacteria represent the most actively growing microorganisms on marsh plant litter in submerged conditions, a finding that contrasts strikingly with results from both standing dead shoots of marsh plants and submerged plant litter decaying in streams. Concomitant measurements of microbial respiration (1.5 to 15.3 mg C-CO 2 g ؊1 of plant litter C day ؊1 ) point to high microbial growth efficiencies on the plant litter, averaging 45.5%. The submerged plant litter layer together with the thin aerobic sediment layer underneath (average depth of 5 mm) contributed the bulk of microbial production per square meter of marsh surface (99%), whereas bacterial production in the marsh water column and epiphytic biofilms was negligible. The magnitude of the combined production in these compartments (ϳ1,490 g C m ؊2 year ؊1 ) highlights the importance of carbon flows through microbial biomass, to the extent that even massive primary productivity of the marsh plants (603 g C m ؊2 year ؊1 ) and subsidiary carbon sources (ϳ330 g C m ؊2 year ؊1 ) were insufficient to meet the microbial carbon demand. These findings suggest that littoral freshwater marshes are genuine hot spots of aerobic microbial carbon transformations, which may act as net organic carbon importers from adjacent systems and, in turn, emit large amounts of CO 2 (here, ϳ870 g C m ؊2 year ؊1 ) into the atmosphere.

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Theoretical and empirical conversion factors for determining bacterial production in freshwater sediments via leucine incorporation

Cited by 45 publications

References 29 publications

Organic substrate quality as the link between bacterioplankton carbon demand and growth efficiency in a temperate salt-marsh estuary

Organic substrate quality as the link between bacterioplankton carbon demand and growth efficiency in a temperate salt-marsh estuary

Infection Paradox: High Abundance but Low Impact of Freshwater Benthic Viruses

Benthic Bacterial and Fungal Productivity and Carbon Turnover in a Freshwater Marsh

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