Biopolymer hydrolysis and bacterial production under ambient hydrostatic pressure through a 2000m water column in the NW Mediterranean

Tamburini, Christian; Garcin, Jean; Ragot, Michel; Bianchi, Armand

doi:10.1016/s0967-0645(02)00030-9

Cited by 99 publications

(88 citation statements)

References 45 publications

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“…6A-D) are in the same range as those obtained in a previous Atlantic study (Baltar et al 2009a), which is the only other study where kinetic parameters have been determined throughout the whole oceanic water column. As in the present study, Baltar et al (2009a) reported a decrease in the V max of LAPase (~12 to 3 nmol l -1 h -1 ) and APase (~0.3 to 0.1 nmol l -1 h -1 ) and an increase in the K m of LAPase (~400 to 1200 µM) and APase (~2 to 23 µM) with depth down to 4500 m. Tamburini et al (2002) obtained lower K m values (ranging between 0.4 and 1.1 µM) for LAPase in the Mediterranean deep-waters (down to 2000 m depth) than in the present study. However, the APase K m values (0.05 to 1.2 µM) reported by Tamburini et al (2002) are in the same range as the APase K m we obtained.…”

Section: Discussionsupporting

confidence: 83%

High dissolved extracellular enzymatic activity in the deep central Atlantic Ocean

Baltar¹,

Arı́stegui²,

Gasol³

et al. 2010

Aquat. Microb. Ecol.

107

120

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The distribution of prokaryotic abundance (PA), prokaryotic heterotrophic production (PHP), and suspended particulate organic material (POM), as well as total and dissolved (operationally defined as passing through 0.2 µm pore size filters) potential extracellular enzymatic activities (EEA; α-and β-glucosidase [AGase and BGase], leucine aminopeptidase [LAPase], and alkaline phosphatase [APase]) were determined in the meso-and bathypelagic waters of the (sub)tropical Atlantic along an eastern zonal transatlantic transect and a western N-S transect. Significant differences between both transects were found for POM concentration but not for PA, PHP (except in the subsurface and oxygen minimum layer), and dissolved and total EEA. PHP decreased by 3 orders of magnitude from the lower euphotic zone to bathypelagic waters, while PA and cell-specific PHP decreased only by 1 and 2 orders of magnitude, respectively. The proportion of the dissolved to the total EEA was high in the dark ocean for all the enzymes, ranging from 54 to 100, 56 to 100, 65 to 100 and 57 to 97% for AGase, BGase, LAPase and APase, respectively. The kinetic parameters (V max and K m ) of both the dissolved and total fractions of LAPase and APase were very similar throughout the water column, suggesting a similar origin for both dissolved and particulate EEA. Significant correlations of both dissolved and total EEA were found with prokaryotic metabolism and the POM pool. Based on the previous notion that the fraction of dissolved EEA is higher in particle-attached than in free-living microbes, our results suggest that microbial activity in the dark ocean occurs mainly on colloidal and particulate material. This is in agreement with recent genomic evidence. However, these colloidal and particulate materials are prone to disruption during the sampling process. Hence, more selective sampling techniques are needed to specifically collect these deep-water aggregates that probably represent hotspots of microbial activity in the deep ocean.

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Section: Discussionsupporting

confidence: 83%

High dissolved extracellular enzymatic activity in the deep central Atlantic Ocean

Baltar¹,

Arı́stegui²,

Gasol³

et al. 2010

Aquat. Microb. Ecol.

107

120

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“…Compared to previous studies at the same JGOFS-DYFAMED station, total bacterial abundance and production values measured during the sampling period (0.53 to 1.83×10 5 cells ml −1 and 0.07 to 8.10 ng C l −1 h −1 for total bacterial abundance and production, respectively; Fig. 4) are comparable to the previous studies driven in the mesopelagic layers of the NW Mediterranean Sea (Turley and Stutt, 2000;Harris et al, 2001;Tamburini et al, 2002;Tanaka and Rassoulzadegan, 2004). The magnitude of depth-dependent decrease of total bacterial abundance was relatively constant for our study period.…”

Section: Temporal Evolution Of High Nucleic Acid Content Cells In Thesupporting

confidence: 83%

Seasonal to hour variation scales in abundance and production of total and particle-attached bacteria in the open NW Mediterranean Sea (0–1000 m)

et al. 2008

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Abstract. We present the vertical and temporal dynamics of total vs. particle-attached bacterial abundance and activity over a 5 week period under summer to autumn transition in NW Mediterranean Sea. At a weekly time scale, total bacterial biomass and production in the euphotic layers was significantly correlated with phytoplanktonic biomass. At an hourly time scale, total bacterial biomass responded very rapidly to chlorophyll a fluctuations, suggesting a tight coupling between phytoplankton and bacteria for resource partitioning during the summer-autumn transition. In contrast, no influence of diel changes on bacterial parameters was detected. Episodic events such as coastal water intrusions had a significant positive effect on total bacterial abundance and production, whereas we could not detect any influence of short wind events whatever the magnitude. Finally, we show that particle-attached bacteria can represent a large proportion (up to 49%) of the total bacterial activity in the euphotic layer but display rapid and sporadic changes at hourly time scales. In the mesopelagic layers, bacterial abundance and production linearly decreased with depth, except some production peaks at 400-750 m. This study underlines the value of large datasets covering different temporal scales to clarify the biogeochemical role of bacteria in the cycling of organic matter in open seawater.

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“…Bacterial communities from deep layers are more likely to colonize these particles than communities from upper layers. Surface bacteria attached to particles are grazed by heterotrophic flagellates during sinking throughout the mesopelagic layer (Tanaka and Rassoulzadegan 2004), whereas bathypelagic bacteria are well adapted to pressure conditions at deep depth (Tholosan et al 1999;Tamburini et al 2002). In these particles however, a few individual biomarkers exhibited significant apparent degradation rate constants (data not shown), suggesting that some molecules carried by the faster settling particles were accessible inside or outside of aggregates to bacterial attack during transport from surface to depth.…”

Section: Biodegradability Of the Different Settling Velocity Classes-mentioning

confidence: 99%

“…At the same time, OM can protect minerals from dissolution at cellular and particulate scales. Bacterial activity enhanced diatom frustule dissolution through ectoenzymatic hydrolysis of the protein membrane surrounding the diatom frustule (Bidle andAzam 1999, 2001); however, in the bathypelagic layers, hydrostatic pressure slows down this process through inhibition of bacterial ectohydrolase (Tamburini et al 2006). At the scale of the particle, when diatoms are embedded inside aggregates in a matrix of degraded OM, dissolution of biogenic silica (BSiO 2 ) decreases (Moriceau et al 2007).…”

mentioning

confidence: 99%

Composition and degradation of marine particles with different settling velocities in the northwestern Mediterranean Sea

Goutx¹,

Wakeham

Lee

et al. 2007

Limnology & Oceanography

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Settling particles were collected from the Ligurian Sea in the northwestern Mediterranean Sea in May 2003 and separated by elutriation into different settling velocity classes (.230, 115-230, 58-115, and ,58 m d 21 ). Particles of the different classes were incubated for 5 d to study their biodegradability. Particulate opal content and organic compound composition (amino acids, pigments, lipids, and carbohydrates) were analyzed initially and at regular time intervals during the incubation period. Most particles (48-67% of total mass) sank at greater than 230 m d 21 and were dominated by large diatom-derived aggregates produced during the spring bloom period. The initial organic composition and the biological lability of these particles varied with settling velocity. The strong phytoplankton signal was visible in all settling velocity classes, while slower settling particles carried with them a greater zooplankton and bacterial signature. As the different class particles decomposed, their compositions changed and became more similar with time, with a dominance of compounds that suggests a more degraded state: the amino acids c-aminobutyric acid and b-alanine, the pigments pyropheophorbide and pheophytin, the deoxysugars fucose and rhamnose, and lipid metabolites (diglycerides and monoglycerides, alcohols, and free fatty acids). Biogenic opal in the particles dissolved faster in more degraded particles than in fresher particles, suggesting that loss of organic matter may expose opal to dissolution. The coupling of settling velocity and decomposition rate measurements shows quantitatively that slower settling particles are quickly degraded and AcknowledgmentsThis research was part of the MedFlux and PECHE (Production and Export of Carbon: Control by Heterotrophs at small temporal scale) programs and was supported by the U.S. National Science Foundation Chemical Oceanography Program (OCE-0136370, OCE-0136318, and OCE-0113687) and the French CNRS (Centre National de la Recherche Scientifique), respectively. Participation of B.M. was funded by ORFOIS (Origin and Fate of Biogetic Particle Fluxes in the ocean) (EVK2-CT2001-00100). We thank Michael Peterson, Lynn Abramson, Jenni Szlosek, Meaghan Askea, and Isabell Putnam for shipboard and laboratory help; David Hirschberg and Michael Peterson for CHN analysis; Claude Mante for help with statistical data treatment; and the captain and crew of the RV Seward Johnson II. We wish to acknowledge the associate editor and two anonymous reviewers for very helpful comments and suggestions on the manuscript. This is MedFlux contribution 7 and MSRC contribution 1318.

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Biopolymer hydrolysis and bacterial production under ambient hydrostatic pressure through a 2000m water column in the NW Mediterranean

Cited by 99 publications

References 45 publications

High dissolved extracellular enzymatic activity in the deep central Atlantic Ocean

High dissolved extracellular enzymatic activity in the deep central Atlantic Ocean

Seasonal to hour variation scales in abundance and production of total and particle-attached bacteria in the open NW Mediterranean Sea (0–1000 m)

Composition and degradation of marine particles with different settling velocities in the northwestern Mediterranean Sea

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