74 research outputs found
Microcystin aids in cold temperature acclimation: Differences between a toxic Microcystis wildtype and non-toxic mutant
For Microcystis aeruginosa PCC 7806, temperature decreases from 26 °C to 19 °C double the microcystin quota per cell during growth in continuous culture. Here we tested whether this increase in microcystin provided M. aeruginosa PCC 7806 with a fitness advantage during colder-temperature growth by comparing cell concentration, cellular physiology, reactive oxygen species damage, and the transcriptomics-inferred metabolism to a non-toxigenic mutant strain M. aeruginosa PCC 7806 ÎmcyB. Photo-physiological data combined with transcriptomic data revealed metabolic changes in the mutant strain during growth at 19 °C, which included increased electron sinks and non-photochemical quenching. Increased gene expression was observed for a glutathione-dependent peroxiredoxin during cold treatment, suggesting compensatory mechanisms to defend against reactive oxygen species are employed in the absence of microcystin in the mutant. Our observations highlight the potential selective advantages of a longer-term defensive strategy in management of oxidative stress (i.e., making microcystin) vs the shorter-term proactive strategy of producing cellular components to actively dissipate or degrade oxidative stress agents
Towards a Processual Microbial Ontology
types: ArticleStandard microbial evolutionary ontology is organized according to a
nested hierarchy of entities at various levels of biological organization. It typically
detects and defines these entities in relation to the most stable aspects of evolutionary
processes, by identifying lineages evolving by a process of vertical inheritance
from an ancestral entity. However, recent advances in microbiology indicate
that such an ontology has important limitations. The various dynamics detected
within microbiological systems reveal that a focus on the most stable entities (or
features of entities) over time inevitably underestimates the extent and nature of
microbial diversity. These dynamics are not the outcome of the process of vertical
descent alone. Other processes, often involving causal interactions between entities
from distinct levels of biological organisation, or operating at different time scales,
are responsible not only for the destabilisation of pre-existing entities, but also for
the emergence and stabilisation of novel entities in the microbial world. In this
article we consider microbial entities as more or less stabilised functional wholes,
and sketch a network-based ontology that can represent a diverse set of processes
including, for example, as well as phylogenetic relations, interactions that stabilise
or destabilise the interacting entities, spatial relations, ecological connections, and
genetic exchanges. We use this pluralistic framework for evaluating (i) the existing
ontological assumptions in evolution (e.g. whether currently recognized entities are
adequate for understanding the causes of change and stabilisation in the microbial
world), and (ii) for identifying hidden ontological kinds, essentially invisible from
within a more limited perspective. We propose to recognize additional classes of
entities that provide new insights into the structure of the microbial world, namely ââprocessually equivalentââ entities, ââprocessually versatileââ entities, and ââstabilizedââ
entities.Economic and Social Research Council, U
A review on substances and processes relevant for optical remote sensing of extremely turbid marine areas, with a focus on the Wadden Sea
The interpretation of optical remote sensing data of estuaries and tidal flat areas is hampered by optical complexity and often extreme turbidity. Extremely high concentrations of suspended matter, chlorophyll and dissolved organic matter, local differences, seasonal and tidal variations and resuspension are important factors influencing the optical properties in such areas. This review gives an overview of the processes in estuaries and tidal flat areas and the implications of these for remote sensing in such areas, using the Wadden Sea as a case study area. Results show that remote sensing research in extremely turbid estuaries and tidal areas is possible. However, this requires sensors with a large ground resolution, algorithms tuned for high concentrations of various substances and the local specific optical properties of these substances, a simultaneous detection of water colour and land-water boundaries, a very short time lag between acquisition of remote sensing and in situ data used for validation and sufficient geophysical and ecological knowledge of the area. © 2010 The Author(s)
Southward displacement of the North Atlantic Subtropical Gyre circulation system during North Atlantic cold spells
Key Points:
- Rapid subsurface oceanographic change in the tropical W Atlantic reflect shifting Subtropical Gyre
- Subsurface warming responds to deglacial AMOC perturbations (Heinrich Stadials 2, 1, and the Younger Dryas)
- Southward propagation of Salinity Maximum Water during Northern Hemisphere cold spells shift the mixing zone of tropical and subtropical waters
During times of deglacial Atlantic Meridional Overturning Circulation (AMOC) perturbations, the tropical Atlantic experienced considerable warming at subsurface levels. Coupled oceanâatmosphere simulations corroborate the tight teleconnection between the tropical Atlantic and climate change at high northern latitudes, but still underestimate the relevance of the subsurface N Atlantic Subtropical Gyre (STG) for heat and salt storage and its sensitivity to rapid climatic change.
We here reconstruct vertical and lateral temperature and salinity gradients in the tropical W Atlantic and the Caribbean over the last 30 kyrs, based on planktic deep and shallow dwelling foraminiferal Mg/Ca and ÎŽ18Oârecords. The rapid and large amplitude subsurface changes illustrate a dynamic STG associated with abrupt shifts of North Atlantic hydrographic and atmospheric regimes. During full glacial conditions, the STG has been shifted southward while intensified Ekmanâdownwelling associated to strengthened trade winds fostered the formation of warm and saline Salinity Maximum Water (SMW). The southward propagation of SMW was facilitated by the glacially eastward deflected North Brazil Current. During periods of significant AMOC perturbations (Heinrich Stadials 1, and the Younger Dryas), extreme subsurface warming by ~6°C led to diminished lateral subsurface temperature gradients. Coevally, a deep thermocline suggests that SMW fully occupied the subsurface tropical W Atlantic and that the STG reached its southernmost position. During the Holocene, modernâlike conditions gradually developed with the northward retreat of SMW and the development of a strong thermocline ridge between the Subtropical Gyre and the tropical W Atlantic
Harmful Elements in Estuarine and Coastal Systems
Estuaries and coastal zones are dynamic transitional systems which provide many economic and ecological benefits to humans, but also are an ideal habitat for other organisms as well. These areas are becoming contaminated by various anthropogenic activities due to a quick economic growth and urbanization. This chapter explores the sources, chemical speciation, sediment accumulation and removal mechanisms of the harmful elements in estuarine and coastal seawaters. It also describes the effects of toxic elements on aquatic flora and fauna. Finally, the toxic element pollution of the Venice Lagoon, a transitional water body located in the northeastern part of Italy, is discussed as a case study, by presenting the procedures adopted to measure the extent of the pollution, the impacts on organisms and the restoration activities
Effects of arsenate (As5+) on growth and production of glutathione (GSH) and phytochelatins (PCs) in Chlorella vulgaris
The effect of arsenate (As5+) on growth and chlorophyll a production in Chlorella vulgaris, its removal by C. vulgaris and the role of glutathione (GSH) and phytochelatins (PCs) were investigated.C. vulgaris was tolerant to As5+ at up to 200 mg/L and was capable of consistently removing around 70% of the As5+ present in growth media over a wide range of exposure concentrations. Spectral analysis revealed that PCs and their arsenic-combined complexes were absent indicating that the high bioaccumulation and tolerance to arsenic observed was not due to intracellular chelation. In contrast, GSH was found in all samples ranging from 0.8 mg/L in the control to 6.5mg/L in media containing 200 mg/L As5+ suggesting that GSH plays a more prominent role in the detoxification of As5+ in C. vulgaris than PC. At concentrations below 100 mg/L cell surface binding and other mechanisms may play the primary role in As5+ detoxification, whereas above this concentration As5+ begins to accumulate inside the algal cells and activates a number of intracellular cell defence mechanisms, such as increased production of GSH. The overall findings complement field studies which suggest C. vulgaris as an increasingly promising low cost As phytoremediation method for developing countries
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