GLORIA

GEOMAR Library Ocean Research Information Access

X

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • Proceedings of the National Academy of Sciences  (10)
  • 1
    Online Resource
    Online Resource
    Wet phases in the Sahara/Sahel region and human migration patterns in North Africa
    Proceedings of the National Academy of Sciences ; 2009
    In:  Proceedings of the National Academy of Sciences Vol. 106, No. 48 ( 2009-12), p. 20159-20163
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 106, No. 48 ( 2009-12), p. 20159-20163
    Abstract: The carbon isotopic composition of individual plant leaf waxes (a proxy for C 3 vs. C 4 vegetation) in a marine sediment core collected from beneath the plume of Sahara-derived dust in northwest Africa reveals three periods during the past 192,000 years when the central Sahara/Sahel contained C 3 plants (likely trees), indicating substantially wetter conditions than at present. Our data suggest that variability in the strength of Atlantic meridional overturning circulation (AMOC) is a main control on vegetation distribution in central North Africa, and we note expansions of C 3 vegetation during the African Humid Period (early Holocene) and within Marine Isotope Stage (MIS) 3 (≈50–45 ka) and MIS 5 (≈120–110 ka). The wet periods within MIS 3 and 5 coincide with major human migration events out of sub-Saharan Africa. Our results thus suggest that changes in AMOC influenced North African climate and, at times, contributed to amenable conditions in the central Sahara/Sahel, allowing humans to cross this otherwise inhospitable region.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.0905771106
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2009
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
    SSG: 11
    SSG: 12
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
  • 2
    Online Resource
    Online Resource
    Redox-dependent niche differentiation provides evidence for multiple bacterial sources of glycerol tetraether lipids in lakes
    Proceedings of the National Academy of Sciences ; 2018
    In:  Proceedings of the National Academy of Sciences Vol. 115, No. 43 ( 2018-10-23), p. 10926-10931
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 115, No. 43 ( 2018-10-23), p. 10926-10931
    Abstract: Terrestrial paleoclimate archives such as lake sediments are essential for our understanding of the continental climate system and for the modeling of future climate scenarios. However, quantitative proxies for the determination of paleotemperatures are sparse. The relative abundances of certain bacterial lipids, i.e., branched glycerol dialkyl glycerol tetraethers (brGDGTs), respond to changes in environmental temperature, and thus have great potential for climate reconstruction. Their application to lake deposits, however, is hampered by the lack of fundamental knowledge on the ecology of brGDGT-producing microbes in lakes. Here, we show that brGDGTs are synthesized by multiple groups of bacteria thriving under contrasting redox regimes in a deep meromictic Swiss lake (Lake Lugano). This niche partitioning is evidenced by highly distinct brGDGT inventories in oxic vs. anoxic water masses, and corresponding vertical patterns in bacterial 16S rRNA gene abundances, implying that sedimentary brGDGT records are affected by temperature-independent changes in the community composition of their microbial producers. Furthermore, the stable carbon isotope composition (δ 13 C) of brGDGTs in Lake Lugano and 34 other (peri-)Alpine lakes attests to the widespread heterotrophic incorporation of 13 C-depleted, methane-derived biomass at the redox transition zone of mesotrophic to eutrophic lake systems. The brGDGTs produced under such hypoxic/methanotrophic conditions reflect near-bottom water temperatures, and are characterized by comparatively low δ 13 C values. Depending on climate zone and water depth, lake sediment archives predominated by deeper water/low- 13 C brGDGTs may provide more reliable records of climate variability than those where brGDGTs derive from terrestrial and/or aquatic sources with distinct temperature imprints.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.1805186115
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2018
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
    SSG: 11
    SSG: 12
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
  • 3
    Online Resource
    Online Resource
    Fossilized glycolipids reveal past oceanic N 2 fixation by heterocystous cyanobacteria
    Proceedings of the National Academy of Sciences ; 2010
    In:  Proceedings of the National Academy of Sciences Vol. 107, No. 45 ( 2010-11-09), p. 19190-19194
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 107, No. 45 ( 2010-11-09), p. 19190-19194
    Abstract: N 2 -fixing cyanobacteria play an essential role in sustaining primary productivity in contemporary oceans and freshwater systems. However, the significance of N 2 -fixing cyanobacteria in past nitrogen cycling is difficult to establish as their preservation potential is relatively poor and specific biological markers are presently lacking. Heterocystous N 2 -fixing cyanobacteria synthesize unique long-chain glycolipids in the cell envelope covering the heterocyst cell to protect the oxygen-sensitive nitrogenase enzyme. We found that these heterocyst glycolipids are remarkably well preserved in (ancient) lacustrine and marine sediments, unambiguously indicating the (past) presence of N 2 -fixing heterocystous cyanobacteria. Analysis of Pleistocene sediments of the eastern Mediterranean Sea showed that heterocystous cyanobacteria, likely as epiphytes in symbiosis with planktonic diatoms, were particularly abundant during deposition of sapropels. Eocene Arctic Ocean sediments deposited at a time of large Azolla blooms contained glycolipids typical for heterocystous cyanobacteria presently living in symbiosis with the freshwater fern Azolla , indicating that this symbiosis already existed in that time. Our study thus suggests that heterocystous cyanobacteria played a major role in adding “new” fixed nitrogen to surface waters in past stratified oceans.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.1007526107
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2010
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
    SSG: 11
    SSG: 12
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
  • 4
    Online Resource
    Online Resource
    Thaumarchaeotes abundant in refinery nitrifying sludges express amoA but are not obligate autotrophic ammonia oxidizers
    Proceedings of the National Academy of Sciences ; 2011
    In:  Proceedings of the National Academy of Sciences Vol. 108, No. 40 ( 2011-10-04), p. 16771-16776
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 108, No. 40 ( 2011-10-04), p. 16771-16776
    Abstract: Nitrification is a core process in the global nitrogen cycle that is essential for the functioning of many ecosystems. The discovery of autotrophic ammonia-oxidizing archaea (AOA) within the phylum Thaumarchaeota has changed our perception of the microbiology of nitrification, in particular since their numerical dominance over ammonia-oxidizing bacteria (AOB) in many environments has been revealed. These and other data have led to a widely held assumption that all amoA -encoding members of the Thaumarchaeota (AEA) are autotrophic nitrifiers. In this study, 52 municipal and industrial wastewater treatment plants were screened for the presence of AEA and AOB. Thaumarchaeota carrying amoA were detected in high abundance only in four industrial plants. In one plant, thaumarchaeotes closely related to soil group I.1b outnumbered AOB up to 10,000-fold, and their numbers, which can only be explained by active growth in this continuous culture system, were two to three orders of magnitude higher than could be sustained by autotrophic ammonia oxidation. Consistently, 14 CO 2 fixation could only be detected in AOB but not in AEA in actively nitrifying sludge from this plant via FISH combined with microautoradiography. Furthermore, in situ transcription of archaeal amoA , and very weak in situ labeling of crenarchaeol after addition of 13 CO 2 , was independent of the addition of ammonium. These data demonstrate that some amoA -carrying group I.1b Thaumarchaeota are not obligate chemolithoautotrophs.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.1106427108
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2011
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
    SSG: 11
    SSG: 12
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
  • 5
    Online Resource
    Online Resource
    A Nitrospira metagenome illuminates the physiology and evolution of globally important nitrite-oxidizing bacteria
    Proceedings of the National Academy of Sciences ; 2010
    In:  Proceedings of the National Academy of Sciences Vol. 107, No. 30 ( 2010-07-27), p. 13479-13484
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 107, No. 30 ( 2010-07-27), p. 13479-13484
    Abstract: Nitrospira are barely studied and mostly uncultured nitrite-oxidizing bacteria, which are, according to molecular data, among the most diverse and widespread nitrifiers in natural ecosystems and biological wastewater treatment. Here, environmental genomics was used to reconstruct the complete genome of “ Candidatus Nitrospira defluvii” from an activated sludge enrichment culture. On the basis of this first-deciphered Nitrospira genome and of experimental data, we show that Ca . N. defluvii differs dramatically from other known nitrite oxidizers in the key enzyme nitrite oxidoreductase (NXR), in the composition of the respiratory chain, and in the pathway used for autotrophic carbon fixation, suggesting multiple independent evolution of chemolithoautotrophic nitrite oxidation. Adaptations of Ca . N. defluvii to substrate-limited conditions include an unusual periplasmic NXR, which is constitutively expressed, and pathways for the transport, oxidation, and assimilation of simple organic compounds that allow a mixotrophic lifestyle. The reverse tricarboxylic acid cycle as the pathway for CO 2 fixation and the lack of most classical defense mechanisms against oxidative stress suggest that Nitrospira evolved from microaerophilic or even anaerobic ancestors. Unexpectedly, comparative genomic analyses indicate functionally significant lateral gene-transfer events between the genus Nitrospira and anaerobic ammonium-oxidizing planctomycetes, which share highly similar forms of NXR and other proteins reflecting that two key processes of the nitrogen cycle are evolutionarily connected.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.1003860107
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2010
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
    SSG: 11
    SSG: 12
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
  • 6
    Online Resource
    Online Resource
    Archaeal nitrification in the ocean
    Proceedings of the National Academy of Sciences ; 2006
    In:  Proceedings of the National Academy of Sciences Vol. 103, No. 33 ( 2006-08-15), p. 12317-12322
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 103, No. 33 ( 2006-08-15), p. 12317-12322
    Abstract: Marine Crenarchaeota are the most abundant single group of prokaryotes in the ocean, but their physiology and role in marine biogeochemical cycles are unknown. Recently, a member of this clade was isolated from a sea aquarium and shown to be capable of nitrification, tentatively suggesting that Crenarchaeota may play a role in the oceanic nitrogen cycle. We enriched a crenarchaeote from North Sea water and showed that its abundance, and not that of bacteria, correlates with ammonium oxidation to nitrite. A time series study in the North Sea revealed that the abundance of the gene encoding for the archaeal ammonia monooxygenase alfa subunit ( amoA ) is correlated with a decline in ammonium concentrations and with the abundance of Crenarchaeota. Remarkably, the archaeal amoA abundance was 1–2 orders of magnitude higher than those of bacterial nitrifiers, which are commonly thought to mediate the oxidation of ammonium to nitrite in marine environments. Analysis of Atlantic waters of the upper 1,000 m, where most of the ammonium regeneration and oxidation takes place, showed that crenarchaeotal amoA copy numbers are also 1–3 orders of magnitude higher than those of bacterial amoA . Our data thus suggest a major role for Archaea in oceanic nitrification.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.0600756103
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2006
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
    SSG: 11
    SSG: 12
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
  • 7
    Online Resource
    Online Resource
    Are Marine Group II Euryarchaeota significant contributors to tetraether lipids in the ocean?
    Proceedings of the National Academy of Sciences ; 2014
    In:  Proceedings of the National Academy of Sciences Vol. 111, No. 41 ( 2014-10-14)
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 111, No. 41 ( 2014-10-14)
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.1416176111
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2014
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
    SSG: 11
    SSG: 12
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
  • 8
    Online Resource
    Online Resource
    Rapid short-term cooling following the Chicxulub impact at the Cretaceous–Paleogene boundary
    Proceedings of the National Academy of Sciences ; 2014
    In:  Proceedings of the National Academy of Sciences Vol. 111, No. 21 ( 2014-05-27), p. 7537-7541
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 111, No. 21 ( 2014-05-27), p. 7537-7541
    Abstract: The mass extinction at the Cretaceous–Paleogene boundary, ∼66 Ma, is thought to be caused by the impact of an asteroid at Chicxulub, present-day Mexico. Although the precise mechanisms that led to this mass extinction remain enigmatic, most postulated scenarios involve a short-lived global cooling, a so-called “impact winter” phase. Here we document a major decline in sea surface temperature during the first months to decades following the impact event, using TEX 86 paleothermometry of sediments from the Brazos River section, Texas. We interpret this cold spell to reflect, to our knowledge, the first direct evidence for the effects of the formation of dust and aerosols by the impact and their injection in the stratosphere, blocking incoming solar radiation. This impact winter was likely a major driver of mass extinction because of the resulting global decimation of marine and continental photosynthesis.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.1319253111
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2014
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
    SSG: 11
    SSG: 12
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
  • 9
    Online Resource
    Online Resource
    Hydrogen peroxide detoxification is a key mechanism for growth of ammonia-oxidizing archaea
    Proceedings of the National Academy of Sciences ; 2016
    In:  Proceedings of the National Academy of Sciences Vol. 113, No. 28 ( 2016-07-12), p. 7888-7893
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 113, No. 28 ( 2016-07-12), p. 7888-7893
    Abstract: Ammonia-oxidizing archaea (AOA), that is, members of the Thaumarchaeota phylum, occur ubiquitously in the environment and are of major significance for global nitrogen cycling. However, controls on cell growth and organic carbon assimilation by AOA are poorly understood. We isolated an ammonia-oxidizing archaeon (designated strain DDS1) from seawater and used this organism to study the physiology of ammonia oxidation. These findings were confirmed using four additional Thaumarchaeota strains from both marine and terrestrial habitats. Ammonia oxidation by strain DDS1 was enhanced in coculture with other bacteria, as well as in artificial seawater media supplemented with α-keto acids (e.g., pyruvate, oxaloacetate). α-Keto acid-enhanced activity of AOA has previously been interpreted as evidence of mixotrophy. However, assays for heterotrophic growth indicated that incorporation of pyruvate into archaeal membrane lipids was negligible. Lipid carbon atoms were, instead, derived from dissolved inorganic carbon, indicating strict autotrophic growth. α-Keto acids spontaneously detoxify H 2 O 2 via a nonenzymatic decarboxylation reaction, suggesting a role of α-keto acids as H 2 O 2 scavengers. Indeed, agents that also scavenge H 2 O 2 , such as dimethylthiourea and catalase, replaced the α-keto acid requirement, enhancing growth of strain DDS1. In fact, in the absence of α-keto acids, strain DDS1 and other AOA isolates were shown to endogenously produce H 2 O 2 (up to ∼4.5 μM), which was inhibitory to growth. Genomic analyses indicated catalase genes are largely absent in the AOA. Our results indicate that AOA broadly feature strict autotrophic nutrition and implicate H 2 O 2 as an important factor determining the activity, evolution, and community ecology of AOA ecotypes.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.1605501113
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2016
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
    SSG: 11
    SSG: 12
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
  • 10
    Online Resource
    Online Resource
    Widespread occurrence of structurally diverse tetraether membrane lipids: Evidence for the ubiquitous presence of low-temperature relatives of hyperthermophiles
    Proceedings of the National Academy of Sciences ; 2000
    In:  Proceedings of the National Academy of Sciences Vol. 97, No. 26 ( 2000-12-19), p. 14421-14426
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 97, No. 26 ( 2000-12-19), p. 14421-14426
    Abstract: Isoprenoid glycerol dialkyl glycerol tetraethers (GDGTs) and branched glycerol dialkyl diethers are main membrane constituents of cultured hyperthermophilic archaea and eubacteria, respectively, and are found in environments with temperatures 〉 60°C. Recently, we developed a new technique for the analysis of intact core tetraether lipids in cell material and sediments. The application of this technique to recent sediments shows that known and newly identified isoprenoid and branched GDGTs are widespread in low-temperature environments ( 〈 20°C) and are structurally far more diverse than previously thought. Their distribution indicates the ubiquitous environmental presence of as yet uncultivated, nonthermophilic organisms that may have independently evolved from hyperthermophilic archaea and eubacteria. The structures of some of the new GDGTs point to the hybridization of both typical archaeal and eubacterial biosynthetic pathways in single organisms.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.97.26.14421
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2000
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
    SSG: 11
    SSG: 12
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...