Bacterial Colonization and Ectoenzymatic Activity in Phytoplankton-Derived Model Particles: Cleavage of Peptides and Uptake of Amino Acids

Unanue, Marian; Azúa, Iñigo; Arrieta, Jesús M.; Labirua-Iturburu, A.; Egea, L.; Iriberri, Juan

doi:10.1007/s002489900068

Cited by 45 publications

(42 citation statements)

References 39 publications

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“…The release of DOC may have boosted the growth rates of free-living bacteria, as previously reported for particular aggregates (Unanue et al 1998). We recovered 25% of the organic carbon released from the diatom and cryptophyte pellets in the non-pellet POC fraction, which includes free-living bacteria, and correlations showed that 50% of the variations in the production of free-living bacteria could be explained by variations in incorporation of carbon into the POC fraction.…”

Section: Discussionsupporting

confidence: 60%

“…Since the average production rates of attached bacteria were 5 orders of magnitude higher than the production rates of free-living bacteria in a similar volume of water, it would appear that cope-286 Thor et al: Carbon release from copepod fecal pellets pod fecal pellets -at least on the basis of productionare microbial hot spots. Nevertheless, this high production may have been due solely to higher bacterial abundance, and we did not record growth rates for bacteria that were confidently higher than those reported for free-living bacteria by Unanue et al (1998). It thus appears that the high ectoenzymatic activity associated with the fecal pellets enhanced release of DOC rather than growth of attached bacteria, similar to the situation for amorphous aggregates (Smith et al 1992).…”

Section: Discussionmentioning

confidence: 62%

Section: Discussionmentioning

confidence: 99%

“…It thus appears that the high ectoenzymatic activity associated with the fecal pellets enhanced release of DOC rather than growth of attached bacteria, similar to the situation for amorphous aggregates (Smith et al 1992). This appears to be a general trait of attached bacteria in the pelagic environment, leading to release of DOM from sinking particles (Cho & Azam 1988, Karner & Herndl 1992, Unanue et al 1998.The activity of glucosaminidase, which catalyzes the hydrolysis of chitin, increased manyfold, reaching a maximum at 48 h on all 3 diets and was, in contrast to the activity of all other enzymes tested, fairly well coupled to the production of attached bacteria. A host of different chitin-hydrolyzing bacteria is present in the marine environment (Osawa & Koga 1995, Kirchman & White 1999.…”

mentioning

confidence: 96%

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Fate of organic carbon released from decomposing copepod fecal pellets in relation to bacterial production and ectoenzymatic activity

Thor

Dam²,

Rogers³

2003

Aquat. Microb. Ecol.

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Fecal pellets were produced by Acartia tonsa fed 14 C-labeled diatom, cryptophyte, and dinoflagellate diets, and were incubated in 1.2 µm-filtered Long Island Sound seawater. Based on the 14 C label, the decrease in fpOC (fecal pellet organic carbon), the release and fate of dissolved organic carbon (DOC) and particulate organic carbon (POC), as well as bacterial production and enzymatic activity, were followed over a 96 h period. fpOC decreased by 9, 14, and 19% d -1 in diatom, cryptophyte, and dinoflagellate pellets, respectively. There was a fast, possibly passive, leakage of DOC from pellets from all 3 diets within a few hours after egestion, which may not have been utilized by attached bacteria. Bacterial production rates were 17, 12, and 31 pg C pellet -1 h -1, on diatom, cryptophyte, and dinoflagellate pellets, respectively. These were 5 orders of magnitude higher than production rates of free-living bacteria, indicating that copepod fecal pellets are hot spots of pelagic microbial production. The high production was caused primarily by high initial bacterial abundances. Accordingly, production and growth were entirely uncoupled in diatom pellets. There were no increases in abundance of attached bacteria on any of the 3 diets, indicating that the produced bacterial cells were released from the fecal pellets. Attached bacteria had a higher ectoenzymatic activity than free-living bacteria, but their production and ectoenzymatic activity were uncoupled and they only assimilated a minor fraction of the released DOC. DOC was therefore released favoring free-living microbes. The chitinase activity, which increased several-fold, was coupled to the production of attached bacteria; thus, chitin may play an important role in bacterial production on copepod fecal pellets.KEY WORDS: Copepod fecal pellets · Fecal pellet decomposition · Pelagic DOC flux · Pelagic POC flux · Attached bacterial production · Ectoenzymatic activity Resale or republication not permitted without written consent of the publisherAquat Microb Ecol 33: [279][280][281][282][283][284][285][286][287][288] 2003 cycled (Wotton & Malmqvist 2001, Turner 2002 and that most carbon originating from these fecal pellets remains part of the long-lived organic carbon in the epipelagic (Legendre & Michaud 1998). Hence, the role of fecal pellets from small copepods is that of supplying nutrients to the epipelagic planktonic microbial community rather than maintaining the vertical flux of organic matter.Copepod fecal pellets host an extensive flora of attached bacteria (Gowing & Silver 1983, Bianchi et al. 1992, Delille & Razouls 1994, Hansen & Bech 1996. Breakdown of the fecal pellets is in part governed by microbial decomposition driven by the hydrolytic activity of these bacteria. The potential hydrolytic activity is generally high in pelagic aggregates of organic matter (Karner & Herndl 1992, Smith et al. 1992, and if this potential is fully exploited in fecal pellets, then decomposition and hence recycling of organic matter may occur rapidly....

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Section: Discussionsupporting

confidence: 60%

Section: Discussionmentioning

confidence: 62%

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 96%

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Fate of organic carbon released from decomposing copepod fecal pellets in relation to bacterial production and ectoenzymatic activity

Thor

Dam²,

Rogers³

2003

Aquat. Microb. Ecol.

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“…The final mode of zooplankton DOC release, from fecal pellets, has been proposed as an important source (Jumars et al 1989, Lampitt et al 1990, Nagata 2000, with as much as 50% of C in pellets being rapidly solubilized (Urban-Rich 1999). Particle-attached bacteria exhibit high hydrolytic activities but are inefficient at utilizing the resulting products, which can lead to large-scale release of organic matter from sinking particles to the dissolved phase (Smith et al 1992, Unanue et al 1998). In common with other models (e.g.…”

Section: Model Descriptionmentioning

confidence: 99%

Microbial loop carbon cycling in ocean environments studied using a simple steady-state model

Anderson¹,

Ducklow²

2001

Aquat. Microb. Ecol.

108

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A simple steady-state model is used to examine the microbial loop as a pathway for organic C in marine systems, constrained by observed estimates of bacterial to primary production ratio (BP:PP) and bacterial growth efficiency (BGE). Carbon sources (primary production including extracellular release of dissolved organic carbon, DOC), cycling via zooplankton grazing and viral lysis, and sinks (bacterial and zooplankton respiration) are represented. Model solutions indicate that, at least under near steady-state conditions, recent estimates of BP:PP of about 0.1 to 0.15 are consistent with reasonable scenarios of C cycling (low BGE and phytoplankton extracellular release) at open ocean sites such as the Sargasso Sea and subarctic North Pacific. The finding that bacteria are a major (50%) sink for primary production is shown to be consistent with the best estimates of BGE and dissolved organic matter (DOM) production by zooplankton and phytoplankton. Zooplankton-related processes are predicted to provide the greatest supply of DOC for bacterial consumption. The bacterial contribution to C flow in the microbial loop, via bacterivory and viral lysis, is generally low, as a consequence of low BGE. Both BP and BGE are hard to quantify accurately. By indicating acceptable combinations of parameter values for given BP:PP, the model provides a simple tool for examining the reliability of BP and BGE estimates. KEY WORDS: Microbial loop · Bacterial production · BGE · Models · DOC · Extracellular release Resale or republication not permitted without written consent of the publisherAquat Microb Ecol 26: [37][38][39][40][41][42][43][44][45][46][47][48][49] 2001 However a recent literature review of BGE in open ocean areas by del Giorgio & Cole (2000) indicates a mean value of 0.15. Replacing the BGE of 0.45 with a BGE of 0.15 in the above calculation gives a BCD:PP of 1.33, which at face value would suggest that in excess of 100% of PP passes through the microbial loop.A number of factors should be taken into consideration when analyzing C flows in this way. Firstly, BP, and hence also BCD, are not constrained by PP, because each C atom can be cycled any number of times around the microbial loop before being respired. Indeed it is possible to construct food-web scenarios in which BP exceeds the input of organic C if growth efficiencies of bacteria and zooplankton are sufficiently high (Strayer 1988). In contrast bacterial respiration (BR), in conjunction with zooplankton respiration (ZR), cannot exceed the supply of organic C. Secondly, alternate sources of organic C should be considered. Most routine 14 C-primary production measurements do not include estimates of the extracellular production of organic carbon (EOC) by exudation or leakage (Bjørnsen 1988), which is an additional source of C for bacteria. There is little consensus on the magnitude and factors controlling EOC in aquatic systems. Expressed as a percentage of extracellular release (PER), this source of DOC typically accounts for about 10% of total pr...

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Enzymatic Activities and Carbon Flux through the Microbial Compartment in the Adriatic Sea

Ferla

Zaccone

Caruso

et al. 2001

Mediterranean Ecosystems

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Bacterial Colonization and Ectoenzymatic Activity in Phytoplankton-Derived Model Particles: Cleavage of Peptides and Uptake of Amino Acids

Cited by 45 publications

References 39 publications

Fate of organic carbon released from decomposing copepod fecal pellets in relation to bacterial production and ectoenzymatic activity

Fate of organic carbon released from decomposing copepod fecal pellets in relation to bacterial production and ectoenzymatic activity

Microbial loop carbon cycling in ocean environments studied using a simple steady-state model

Enzymatic Activities and Carbon Flux through the Microbial Compartment in the Adriatic Sea

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