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  • Bacterial utilization  (1)
  • Diversity  (1)
  • Light  (1)
  • 1
    ISSN: 1573-5052
    Keywords: Bacterial utilization ; Bacterioplankton ; Dissolved organic matter (DOM) ; Radiation ; Ultraviolet-B (UV-B)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Attenuation of ultraviolet (UV)-radiation into the water column is highly correlated with the concentration of the dissolved organic matter (DOM). Thus UV penetrates deeper into marine waters than into freshwater systems. DOM is efficiently cleaved by solar surface radiation levels consuming more oxygen than bacterial metabolism. This photolytically cleaved DOM exhibits higher absorbance ratios (250/365 nm) than untreated DOM. Natural bacterioplankton reach higher abundance if inoculated in previously solar-exposed DOM than in untreated DOM; during bacterial growth the absorbance ratio declines steadily indicating the utilization of the photolytically cleaved DOM. On the other hand, bacterioplankton are greatly reduced in their activity if exposed to surface solar radiation levels. Photoenzymatic repair of DNA induced by UV-A radiation, however, leads to an efficient recovery of bacterial activity once the UV-B stress is released. Turbulent mixing of the upper layers of the water column leads to a continuous alteration of the UV exposure regime. Close to the surface, bacteria and DOM are exposed to high levels of UV-B leading to a reduction in bacterial activity and to photolysis of DOM. Once mixed into deeper layers where UV-B is attenuated, but sufficient UV-A is remaining to allow photoenzymatic repair, the photolytically cleaved DOM is efficiently taken up by bacterioplankton leading to even higher bacterial activity than prior to the exposure. Thus, the overall effect of UV on bacterioplankton is actually an enhancement of bacterial activity despite their lack of protective pigments.
    Type of Medium: Electronic Resource
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  • 2
    Publication Date: 2022-05-25
    Description: Author Posting. © Inter-Research, 2008. This article is posted here by permission of Inter-Research for personal use, not for redistribution. The definitive version was published in Aquatic Microbial Ecology 53 (2008): 21-38, doi:10.3354/ame01230.
    Description: We now have a relatively good idea of how bulk microbial processes shape the cycling of organic matter and nutrients in the sea. The advent of the molecular biology era in microbial ecology has resulted in advanced knowledge about the diversity of marine microorganisms, suggesting that we might have reached a high level of understanding of carbon fluxes in the oceans. However, it is becoming increasingly clear that there are large gaps in the understanding of the role of bacteria in regulating carbon fluxes. These gaps may result from methodological as well as conceptual limitations. For example, should bacterial production be measured in the light? Can bacterial production conversion factors be predicted, and how are they affected by loss of tracers through respiration? Is it true that respiration is relatively constant compared to production? How can accurate measures of bacterial growth efficiency be obtained? In this paper, we discuss whether such questions could (or should) be addressed. Ongoing genome analyses are rapidly widening our understanding of possible metabolic pathways and cellular adaptations used by marine bacteria in their quest for resources and struggle for survival (e.g. utilization of light, acquisition of nutrients, predator avoidance, etc.). Further, analyses of the identity of bacteria using molecular markers (e.g. subgroups of Bacteria and Archaea) combined with activity tracers might bring knowledge to a higher level. Since bacterial growth (and thereby consumption of DOC and inorganic nutrients) is likely regulated differently in different bacteria, it will be critical to learn about the life strategies of the key bacterial species to achieve a comprehensive understanding of bacterial regulation of C fluxes. Finally, some processes known to occur in the microbial food web are hardly ever characterized and are not represented in current food web models. We discuss these issues and offer specific comments and advice for future research agendas.
    Description: Our work was supported by the following grants: NSF grant 0217282 (H.D.), Spanish MEC grant MODIVUS (J.M.G.), the Swedish Science Council (J.P.), the IEO time-series RADIALES programme (X.A.G.M.), the Earth and Life Science Division of the Dutch Science Foundation, ARCHIMEDES project, #835.20.023 (G.J.H.).
    Keywords: Carbon flux ; Microbial ecology ; Ocean ; Bacteria ; Protists ; Light ; Genomics ; Chemoautotrophy ; Models
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Format: application/pdf
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  • 3
    Publication Date: 2022-05-26
    Description: Author Posting. © Inter-Research, 2009. This article is posted here by permission of Inter-Research for personal use, not for redistribution. The definitive version was published in Aquatic Microbial Ecology 55 (2009): 189-201, doi:10.3354/ame01294.
    Description: Pelagic archaeal phylogenetic diversity and the potential for crenarchaeotal nitrification of Group 1.1a were determined in the rivers Rhine and Têt by 16S rRNA sequencing, catalyzed reported deposition-fluorescence in situ hybridization (CARD–FISH) and quantification of 16S rRNA and functional genes. Euryarchaeota were, for the first time, detected in temperate river water even though a net predominance of crenarchaeotal phylotypes was found. Differences in phylogenic distribution were observed between rivers and seasons. Our data suggest that a few archaeal phylotypes (Euryarchaeota Groups RC-V and LDS, Crenarchaeota Group 1.1a) are widely distributed in pelagic riverine environments whilst others (Euryarchaeota Cluster Sagma-1) may only occur seasonally in river water. Crenarchaeota Group 1.1a has recently been identified as a major nitrifier in the marine environment and phylotypes of this group were also present in both rivers, where they represented 0.3% of the total pelagic microbial community. Interestingly, a generally higher abundance of Crenarchaeota Group 1.1a was found in the Rhine than in the Têt, and crenarchaeotal ammonia monooxygenase gene (amoA) was also detected in the Rhine, with higher amoA copy numbers measured in February than in September. This suggests that some of the Crenarchaeota present in river waters have the ability to oxidize ammonia and that riverine crenarchaeotal nitrification of Group 1.1a may vary seasonally.
    Description: The present study is part of the Land–Ocean Interactions in the Coastal Zone (LOICZ) project supported by the Research Council for Earth and Life Science (ALW), with financial aid from the Netherlands Organisation for Scientific Research (NWO) (grant no. 014.27.003 to J.S.S.D.).
    Keywords: Archaea ; River ; Diversity ; Nitrification
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Format: application/pdf
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