Ultrastructure of bacteria and the proportion of Gram-negative bacteria in marine sediments

Moriarty, David; Hayward, A. C.

doi:10.1007/bf02011456

Cited by 85 publications

(48 citation statements)

References 24 publications

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“…Previous work suggests that G+ bacteria are more prominent in deeper (anaerobic) sediments (Moriarty & Hayward 1982, Gontang et al 2007. Since the present study used sandy photic sediments, we assumed that the contribution from G+ bacteria was negligible.…”

Section: Methodsmentioning

confidence: 97%

Fate of macroalgae in benthic systems: carbon and nitrogen cycling within the microbial community

Hardison

Canuel

Anderson

et al. 2010

Mar. Ecol. Prog. Ser.

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High nutrient loading to coastal bays is often accompanied by the presence of bloomforming macroalgae, which take up and sequester large amounts of C and N while growing. This pool is temporary, however, as nuisance macroalgae exhibit a bloom and die-off cycle, influencing the biogeochemical functioning of these systems in unknown ways. The objective of this study was to trace the C and N from senescing macroalgae into relevant sediment pools. A macroalgal die-off event was simulated by the addition of freeze-dried macroalgae (Gracilaria spp.), pre-labeled with stable isotopes ( 13 C and 15 N), to sediment mesocosms. The isotopes were traced into bulk sediments and partitioned into benthic microalgal (BMA) and bacterial biomass using microbial biomarkers to quantify the uptake and retention of macroalgal C and N. Bulk sediments took up label immediately following the die-off, and macroalgal C and N were retained in the sediments for at least 2 wk. Approximately 6 to 50% and 2 to 9% of macroalgal N and C, respectively, were incorporated into the sediments. Label from the macroalgae appeared in both bacterial and BMA biomarkers, suggesting that efficient shuttling of macroalgal C and N between these communities may serve as a mechanism for retention of macroalgal nutrients within the sediments. KEY WORDS: Stable isotopes · Macroalgae · Benthic microalgae · Bacteria · Biomarker · Coastal eutrophication Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 414: [41][42][43][44][45][46][47][48][49][50][51][52][53][54][55] 2010 Studies of macroalgal bloom decay have demonstrated rapid breakdown of biomass, resulting in release of both inorganic and organic nutrients to the water column (Buchsbaum et al. 1991, Castaldelli et al. 2003, García-Robledo et al. 2008, supporting phytoplankton and bacterial metabolism , Nedergaard et al. 2002. Fewer studies have focused on macroalgal decay within the sediments (Nedergaard et al. 2002, Lomstein et al. 2006, Rossi 2007, García-Robledo et al. 2008, where heterotrophic bacterial densities are significantly higher than in the water column (Deming & Baross 1993, Schmidt et al. 1998, Ducklow 2000. In addition, most of the sediment studies have been conducted in low or no light environments, even though light is typically available to shallow sediments where macroalgal die-offs occur and sediment biogeochemistry is largely affected by benthic microalgal (BMA) activity (Underwood & Kromkamp 1999). While nutrients associated with senescent macroalgal blooms are recycled and can have a positive feedback on phytoplankton production in the water column, nutrients released during macroalgal decay in the sediments may support BMA and bacterial production, which could intercept the return of nutrients to the overlying water column. Thus if shallow-water sediments behave as a nutrient filter, the response by phytoplankton may be reduced, and benthic production could effectively buffer the system from further eutrophication. In order to be...

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Section: Methodsmentioning

confidence: 97%

Fate of macroalgae in benthic systems: carbon and nitrogen cycling within the microbial community

Hardison

Canuel

Anderson

et al. 2010

Mar. Ecol. Prog. Ser.

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“…7A). However, because bacterial populations in anoxic sediments are dominated by G Ϫ bacteria (Moriarty and Hayward 1982), the content of THAA pep based on the calculation with the G ϩ bacterium S. aureus probably is biased.…”

Section: Content Of Poc Pon Thaa Dcaa and Dfaa-mentioning

confidence: 99%

“…In addition to L-amino acids, the peptide interbridges may include Damino acids other than D-Ala and D-Glu (e.g., D-aspartate [D-Asp] and D-leucine; Brückner et al 1994). Bacterial populations in marine environments typically have a dominance of G Ϫ to G ϩ bacteria at both oxic (Hagström et al 2000) and anoxic conditions (Moriarty and Hayward 1982). This means that most D-amino acids in marine environments probably are derived from G Ϫ cell walls; thus, the ability of G Ϫ peptidoglycan to degrade is of major importance to the preservation of D-amino acids in these environments.…”

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Bacterial influence on amino acid enantiomerization in a coastal marine sediment

Pedersen

Thomsen

Lomstein

et al. 2001

Limnology & Oceanography

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The contribution of D-isomers of aspartate (Asp), glutamate (Glu), alanine (Ala), and serine (Ser) to the total concentrations of dissolved free amino acids (DFAA), dissolved combined amino acids (DCAA), and total hydrolyzable amino acids (THAA) was studied in a Ͻ2,300-yr-old coastal sediment. Concentrations of the different amino acid pools were typically 5 (DFAA), 100 (DCAA), and 20,000 nmol cm Ϫ3 (THAA), but variable amounts occurred, especially in the surface layer. D-amino acids were identified in all three amino acid fractions. The highest concentration of D-isomers occurred in the THAA fraction at a depth of 10 cm, where the maximum bacterial density has been observed (Jørgensen et al. 1990; Mar. Ecol. Prog. Ser. 59: 39-54). This coincidence suggests that the D-amino acids originated in peptidoglycan of bacterial cell walls. The proportion of D-Asp, D-Glu, D-Ala, and D-Ser increased through the pools of DFAA and DCAA to THAA, suggesting a selective removal of L-amino acids to D-amino acids. The percentage of the four D-amino acids in the THAA pool increased with sediment depth to at least 4.3 m (ϳ2,150 yr). This most likely indicated that peptidoglycan THAA were retained for a longer period of time in a particulate form compared to other proteinaceous material. The contribution of THAA from peptidoglycan to the THAA pool was estimated to range from Ͼ9% at the surface to at least 18% at 4.3 m deep, depending on the assumptions used in the calculation. The distribution of amino acid isomers in Aarhus Bay sediment demonstrated that bacterial peptidoglycan contributed to the pool of organic nitrogen (the four analyzed D-amino acids made up about 3% of particulate organic nitrogen [PON]). Although the peptidoglycan concentration increased with sediment depth, our observations do not indicate a long-term accumulation of peptidoglycan-derived amino acids.

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“…If we assume that the observed D-amino acid profiles (Fig. 2) reflect living bacteria only, published D/L ratios from bacterial cultures (Pedersen et al 2001) (D/L LB ) can be used to estimate the contribution of amino acids from living bacteria (AA LB ) to the measured THAA as ⌺ (D ϫ (1 ϩ (D/L) )), by taking into account Ϫ1 LB that gram-negatives make up ϳ90% of the total bacterial community in aerobic surface sediments and ϳ70% in anaerobic, deeper sediment layers (Moriarty and Hayward 1982). The weighed average D/L ratio for aspartic acid, glutamic acid, serine, and alanine was, respectively 0.064, 0.103, 0.005, and 0.062.…”

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confidence: 99%

Preservation of amino acids from in situ‐produced bacterial cell wall peptidoglycans in northeastern Atlantic continental margin sediments

Grutters

Raaphorst

Epping

et al. 2002

Limnology & Oceanography

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In this study we present the results of total hydrolysable amino acids (THAA) and amino acid D/L‐enantiomers in northeastern Atlantic continental margin sediments. There is increasing evidence that intrinsically labile amino acids are present in old marine sediments as part of a refractory network of peptide‐like material. We used amino acid enantiomers to identify the contribution of amino acids from bacterial cell walls to THAA in organic matter ranging from relatively young to 18,000 yr old. The ratio of D/L‐amino acids increased with depth in the sediment mixed layer. Application of a transport‐racemization‐degradation model excludes a significant production of D‐amino acids by racemization and implies in situ bacterial production as the main source. Amino acids associated with a refractory pool of bacterial cell walls could account for approximately one third of the THAA deeper in the sediments. We propose that in situ bacterial production and the primary flux of labile organic matter from the water column result in a small but highly reactive pool of amino acids in the surface mixed sediment only, whereas amino acids associated with refractory cell walls persist in marine sediments.

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Ultrastructure of bacteria and the proportion of Gram-negative bacteria in marine sediments

Cited by 85 publications

References 24 publications

Fate of macroalgae in benthic systems: carbon and nitrogen cycling within the microbial community

Fate of macroalgae in benthic systems: carbon and nitrogen cycling within the microbial community

Bacterial influence on amino acid enantiomerization in a coastal marine sediment

Preservation of amino acids from in situ‐produced bacterial cell wall peptidoglycans in northeastern Atlantic continental margin sediments

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