scholarly journals Microbial Growth and Organic Matter Cycling in the Pacific Ocean Along a Latitudinal Transect Between Subarctic and Subantarctic Waters

2021 ◽  
Vol 8 ◽  
Author(s):  
Helge-Ansgar Giebel ◽  
Carol Arnosti ◽  
Thomas H. Badewien ◽  
Insa Bakenhus ◽  
John Paul Balmonte ◽  
...  

The Pacific Ocean constitutes about half of the global oceans and thus microbial processes in this ocean have a large impact on global elemental cycles. Despite several intensely studied regions large areas are still greatly understudied regarding microbial activities, organic matter cycling and biogeography. Refined information about these features is most important to better understand the significance of this ocean for global biogeochemical and elemental cycles. Therefore we investigated a suite of microbial and geochemical variables along a transect from the subantarctic to the subarctic Pacific in the upper 200 m of the water column. The aim was to quantify rates of organic matter processing, identify potential controlling factors and prokaryotic key players. The assessed variables included abundance of heterotrophic prokaryotes and cyanobacteria, heterotrophic prokaryotic production (HPP), turnover rate constants of amino acids, glucose, and acetate, leucine aminopeptidase and β-glucosidase activities, and the composition of the bacterial community by fluorescence in situ hybridization (FISH). The additional quantification of nitrate, dissolved amino acids and carbohydrates, chlorophyll a, particulate organic carbon and nitrogen (POC, PON) provided a rich environmental context. The oligotrophic gyres exhibited the lowest prokaryotic abundances, rates of HPP and substrate turnover. Low nucleic acid prokaryotes dominated in these gyres, whereas in temperate and subpolar regions further north and south, high nucleic acid prokaryotes dominated. Turnover rate constants of glucose and acetate, as well as leucine aminopeptidase activity, increased from (sub)tropical toward the subpolar regions. In contrast, HPP and bulk growth rates were highest near the equatorial upwelling and lowest in the central gyres and subpolar regions. The SAR11 clade, the Roseobacter group and Flavobacteria constituted the majority of the prokaryotic communities. Vertical profiles of the biogeochemical and microbial variables markedly differed among the different regions and showed close covariations of the microbial variables and chlorophyll a, POC and PON. The results show that hydrographic, microbial, and biogeochemical properties exhibited distinct patterns reflecting the biogeographic provinces along the transect. The microbial variables assessed contribute to a better and refined understanding of the scales of microbial organic matter processing in large areas of the epipelagic Pacific beyond its well-studied regions.

2000 ◽  
Vol 66 (11) ◽  
pp. 4829-4833 ◽  
Author(s):  
Cleber C. Ouverney ◽  
Jed A. Fuhrman

ABSTRACT Archaea are traditionally thought of as “extremophiles,” but recent studies have shown that marine planktonic Archaea make up a surprisingly large percentage of ocean midwater microbial communities, up to 60% of the total prokaryotes. However, the basic physiology and contribution of Archaea to community microbial activity remain unknown. We have studied Archaea from 200-m depths of the northwest Mediterranean Sea and the Pacific Ocean near California, measuring the archaeal activity under simulated natural conditions (8 to 17°C, dark and anaerobic) by means of a method called substrate tracking autoradiography fluorescence in situ hybridization (STARFISH) that simultaneously detects specific cell types by 16S rRNA probe binding and activity by microautoradiography. In the 200-m-deep Mediterranean and Pacific samples, cells binding the archaeal probes made up about 43 and 14% of the total countable cells, respectively. Our results showed that the Archaea are active in the uptake of dissolved amino acids from natural concentrations (nanomolar) with about 60% of the individuals in the archaeal communities showing measurable uptake. Bacteria showed a similar proportion of active cells. We concluded that a portion of these Archaea is heterotrophic and also appears to coexist successfully with Bacteria in the same water.


1989 ◽  
Vol 16 (9) ◽  
pp. 991-994 ◽  
Author(s):  
Ellen R. M. Druffel ◽  
Peter M. Williams ◽  
Yoshimi Suzuki

1970 ◽  
Vol 50 (2) ◽  
pp. 233-241 ◽  
Author(s):  
F. J. SOWDEN

The amino acids set free by proteolytic enzymes were determined with an amino acid analyzer. Soil and enzyme blanks were subtracted. Pronase released 2 to 10% of the aspartic acid + asparagine, threonine, serine, glutamic acid + glutamine, glycine, lysine and histidine in some fractions of soil organic matter along with 15–35% of the alanine, valine, isoleucine, leucine, tyrosine, phenylalanine and arginine. There was no release of proline, ornithine or ammonia. When the pronase hydrolysate was treated with leucine amino-peptidase, 15% of the proline was released, the yield of glycine was raised from 2 to 14% and the amount of the acidic amino acids was also higher. Acid hydrolysis of the pronase hydrolysate also released more amino acid material but the blanks were much higher than with leucine aminopeptidase. The results suggested that more than half of the aspartic and glutamic acids found on acid hydrolysis were present in the soil organic matter fractions as asparagine and glutamine. The action of pronase on the organic matter of the intact soil was slight, even in the presence of a complexing agent. Papain released very little amino acid material from organic matter fractions, but leucine aminopeptidase or HCl hydrolysis of the papain hydrolysate released about 10% of the amino acid of the fraction, indicating that significant amounts of peptides were formed on papain treatment.


2021 ◽  
Author(s):  
Birgit Gaye ◽  
Niko Lahajnar ◽  
Natalie Harms ◽  
Sophie Anna Luise Paul ◽  
Tim Rixen ◽  
...  

Abstract. Amino acids (AA) mainly bound in proteins are major constituents of living biomass and non-living organic material in the oceanic particulate and dissolved organic matter pool. Uptake and cycling by heterotrophic organisms lead to characteristic changes in AA composition so that AA based biogeochemical indicators are often used to elucidate processes of organic matter cycling and degradation. We analyzed particulate AA in a large sample set collected in various oceanic regions covering sinking and suspended particles in the water column, sediment samples as well as dissolved AA from water column and pore water samples. The aim of this study was to test and improve the use of AA derived biogeochemical indicators as proxies for organic matter sources and degradation, and to better understand particle dynamics and interaction between the dissolved and particulate organic matter pools. A principal component analysis (PCA) of all data delineates diverging AA compositions of sinking and suspended particles with increasing water depth. A new sinking particle and sediment degradation indicator (SDI) allows a fine-tuned classification of sinking particles and sediments with respect to the intensity of degradation, which is associated with changes of bulk δ15N ratios. This new indicator furthermore is sensitive to sedimentary redox conditions and can be used to detect past anoxic early diagenesis. A second indicator emerges from the AA spectra of suspended particulate matter (SPM) in the epipelagic and that of the meso- and bathypelagic ocean and is a residence time indicator (RTI). The characteristic changes in AA patterns from shallow to deep SPM are recapitulated in the AA spectra of the dissolved organic matter (DOM) pool, so that deep SPM is more similar to DOM than to any of the other organic matter pools. This implies that there is equilibration between finely dispersed SPM and DOM in the deep sea, which may be driven by microbial activity combined with annealing and fragmentation of gels. As these processes strongly depend on physico-chemical conditions in the deep ocean, changes in quality and degradability of DOM may strongly affect the relatively large pool of suspended and dissolved AA in the ocean that amounts to 15 Pg amino acid carbon (AAC) and 89 ± 29 Pg AAC, respectively.  


2021 ◽  
Author(s):  
Birgit Gaye ◽  
Niko Lahajnar ◽  
Natalie Harms ◽  
Sophie Anna Luise Paul ◽  
Tim Rixen ◽  
...  

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