Diurnal variations of dissolved and colloidal organic carbon and trace metals in a boreal lake during summer bloom

Pokrovsky, Oleg S.; Shirokova, Liudmila S.

doi:10.1016/j.watres.2012.11.017

Cited by 53 publications

(36 citation statements)

References 83 publications

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“…Relative to the other clock proteins, CikA is poorly conserved across, and absent from, many cyanobacteria (21). Admittedly, circadian rhythms have not been characterized in most of these species, although diel behaviors are widespread (22)(23)(24)(25). A reduced network that lacks kaiA and cikA has been shown to produce strong diel rhythms in the cyanobacteria Prochlorococcus marinus MED4, suggesting that CikA is indeed not necessary for daily timing (21,26).…”

Section: Discussionmentioning

confidence: 99%

Single mutations in sasA enable a simpler Δ cikA gene network architecture with equivalent circadian properties

Shultzaberger

Boyd

Katsuki

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

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The circadian input kinase of the cyanobacterium Synechococcus elongatus PCC 7942 (CikA) is important both for synchronizing circadian rhythms with external environmental cycles and for transferring temporal information between the oscillator and the global transcriptional regulator RpaA (regulator of phycobilisome-associated A). KOs of cikA result in one of the most severely altered but still rhythmic circadian phenotypes observed. We chemically mutagenized a cikA-null S. elongatus strain and screened for second-site suppressor mutations that could restore normal circadian rhythms. We identified two independent mutations in the Synechococcus adaptive sensor A (sasA) gene that produce nearly WT rhythms of gene expression, likely because they compensate for the loss of CikA on the temporal phosphorylation of RpaA. Additionally, these mutations restore the ability to reset the clock after a short dark pulse through an output-independent pathway, suggesting that SasA can influence entrainment through direct interactions with KaiC, a property previously unattributed to it. These experiments question the evolutionary advantage of integrating CikA into the cyanobacterial clock, challenge the conventional construct of separable input and output pathways, and show how easily the cell can adapt to restore phenotype in a severely compromised genetic network.gene network | cyanobacteria | evolution S econd-site suppressor mutagenesis screens have been useful in untangling the genetic components and pathways that underlie complex cellular phenotypes (1). By understanding how mutations in one gene can compensate for changes in another, we can infer how those genes interact with each other and with their encompassing genetic network. We used this approach to better understand the genetic determination of circadian rhythms in the cyanobacterium Synechococcus elongatus PCC 7942. Because the core clock genes in this species exist as single copies, suppressing mutations are not buffered by paralogs, making S. elongatus ideal for this type of mutagenic assay. Approximately 15 genes have been identified that influence the circadian phenotype to various degrees, the most important of which are the kai genes: kaiA, kaiB, and kaiC. In cyanobacteria, time is kept through the central oscillator protein KaiC, whose phosphorylation state, conformation, and ATPase activity, which are mediated by interactions with KaiA and KaiB, cycle within a 24-h period (2-4). The temporal phosphorylation of KaiC can be reconstituted in vitro by simply combining the three Kai proteins and ATP, suggesting that time is kept primarily through a posttranslational mechanism (5). Although the Kai oscillator functions relatively robustly in isolation, additional proteins are necessary to synchronize the oscillations with the environment (entrainment) through the detection of cellular and environmental cues (input pathway) and to transfer temporal information from the oscillator to circadian-dependent transcriptional regulators (output pathway). One of these prot...

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Section: Discussionmentioning

confidence: 99%

Single mutations in sasA enable a simpler Δ cikA gene network architecture with equivalent circadian properties

Shultzaberger

Boyd

Katsuki

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

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“…The international geostandards SLRS-4 and SLRS-5 (Riverine Water Reference Material for Trace Metals certified by the National Research Council of Canada) were used to check the validity and reproducibility of each analysis (see refs. [10][11][12] for analytical pH was measured in the field using a combined electrode calibrated against NIST (National Institute of Standards and Technology, Gaithersburg, MD, USA) buffer solutions (pH = 4.00 and 6.86 at 25˝C). The accuracy of pH measurements was˘0.02 pH units.…”

Section: Study Site Description Sampling Methods and Analysismentioning

confidence: 99%

“…The international geostandards SLRS-4 and SLRS-5 (Riverine Water Reference Material for Trace Metals certified by the National Research Council of Canada) were used to check the validity and reproducibility of each analysis (see refs. [10][11][12] for analytical details). There was good agreement between our replicated measurements of SLRS-5 and the certified values (relative difference <15%).…”

Section: Study Site Description Sampling Methods and Analysismentioning

confidence: 99%

“…In particular, we demonstrated the impact of the anomalously hot summer in 2010 on the increase of low molecular weight (potentially bioavailable) forms of dissolved organic carbon (DOC) and metals, primarily linked to enhanced photo-and bio-degradation of large size allochthonous soil dissolved organic matter (DOM) coupled with production of phytoplankton exometabolites [10]. In addition, observations of the diel photosynthetic cycle of the shallow zone of this lake during the hot summer's cyanobacterial bloom revealed the existence of coupled DOC-Fe-Mn speciation cycle in the surface water layer linked to alternative photosynthetic activity and heterotrophic aerobic plankton respiration [11]. In contrast to rather detailed understanding of lake water hydrochemistry and mechanisms regulating the biogeochemical cycle of organic carbon during recent years, the evolution of the lake ecosystem over past decades remains poorly known.…”

Section: Introductionmentioning

confidence: 99%

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Small Boreal Lake Ecosystem Evolution under the Influence of Natural and Anthropogenic Factors: Results of Multidisciplinary Long-Term Study

Shirokova

Vorobieva

Zabelina

et al. 2016

Water

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Small aquatic ecosystems of the boreal zone are known to be most sensitive indicators of on-going environmental change as well as local anthropogenic pressure, while being highly vulnerable to external impacts. Compared to rather detailed knowledge of the evolution of large and small lakes in Scandinavia and Canada, and large lakes in Eurasia, highly abundant small boreal lakes of northwest Russia have received very little attention, although they may become important centers of attraction of growing rural population in the near future. Here we present the results of a multidisciplinary, multi-annual study of a small boreal humic lake of NW Russia. A shallow (3 m) and a deep (16 m) site of this lake were regularly sampled for a range of chemical and biological parameters. Average multi-daily, summer-time values of the epilimnion (upper oxygenated) layer of the lake provided indications of possible trends in temperature, nutrients, and bacterio-plankton concentration that revealed the local pollution impact in the shallow zone and overall environmental trend in the deep sampling point of the lake. Organic phosphorus, nitrate, and lead were found to be most efficient tracers of local anthropogenic pollution, especially visible in the surface layer of the shallow site of the lake. Cycling of trace elements between the epilimnion and hypolimnion is tightly linked to dissolved organic matter speciation and size fractionation due to the dominance of organic and organo-ferric colloids. The capacity of lake self-purification depends on the ratio of primary productivity to mineralization of organic matter. This ratio remained >1 both during winter and summer periods, which suggests a high potential of lake recovery from the input of allochthonous dissolved organic matter and local anthropogenic pollution.

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“…and Gloeocapsa sp. cyanobacteria were produced on EDTA-free BG-11 media at pH=8.0-8.2 and T=28-30ºC as described previously (Martinez et al 2008(Martinez et al , 2010Mavromatis et al, 2012;Shirokova et al, 2013;Bundeleva et al, 2014). The growth phase was characterized by measuring optical density and cell biomass versus time.…”

Section: Adsorption Experimentsmentioning

confidence: 99%

Iron isotope fractionation during Fe(II) and Fe(III) adsorption on cyanobacteria

et al. 2015

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Diurnal variations of dissolved and colloidal organic carbon and trace metals in a boreal lake during summer bloom

Cited by 53 publications

References 83 publications

Single mutations in sasA enable a simpler Δ cikA gene network architecture with equivalent circadian properties

Single mutations in sasA enable a simpler Δ cikA gene network architecture with equivalent circadian properties

Small Boreal Lake Ecosystem Evolution under the Influence of Natural and Anthropogenic Factors: Results of Multidisciplinary Long-Term Study

Iron isotope fractionation during Fe(II) and Fe(III) adsorption on cyanobacteria

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