From April 2012 to January 2013 (over four seasons), in situ microcosm experiments were conducted in Lake Taihu, perturbed over a range of pCO sub(2) scenarios (270, 380, and 750 mu atm; 1 atm = ...101.325 kPa). The influence of CO sub(2) level on microcosms was greatest during the spring because of the high growth rate of phytoplankton. In this season, rising CO sub(2) levels caused a pH reduction, and the maximum reduction was 0.6 units when CO sub(2) level was enhanced from the present level to 750 mu atm. The doubling of CO sub(2) level could increase the net primary production (NPP) by 65% during spring when the concentrations of other nutrients were maintained. The rise of NPP could cause a decline of dissolved inorganic carbon (DIC) concentration, and CO sub(2) enrichment might mitigate the extent of this decline. Meanwhile, higher CO sub(2) may slow or prevent a loss of diversity of phytoplankton in microcosms in this season. During the other three seasons, Microcystis predominated, and the percentage of cyanobacteria did not alter with the change of CO sub(2). We did not observe a significant increase in the abundance of any taxa with the rise of CO sub(2) during the in situ microcosm experiments.Original Abstract: D'avril 2012 a janvier 2013 (quatre saisons), des experiences en microcosmes in situ ont ete menees dans le lac Taihu, les microcosmes etant perturbes de maniere a couvrir une fourchette de scenarios de pCO sub(2) (270, 380 et 750 mu atm; 1 atm = 101.325 kPa). L'influence des niveaux de CO sub(2) sur les microcosmes etait la plus grande au printemps en raison du taux de croissance eleve du phytoplancton. Durant cette saison, l'augmentation des concentrations de CO sub(2) causait une reduction du pH, la reduction maximum etant de 0,6 unite quand la concentration de CO sub(2) etait rehaussee a 750 mu atm. Le fait de doubler la concentration de CO sub(2) pouvait se traduire par une augmentation de 65 % de la production primaire nette (PPN) au printemps, quand les concentrations d'autres nutriments etaient maintenues constantes. L'augmentation de la PPN pouvait causer une diminution de la concentration de carbone inorganique dissous (CID) dans l'eau et l'augmentation du CO sub(2) pouvait attenuer l'ampleur de cette diminution. Par ailleurs, des teneurs en CO sub(2) plus elevees pouvaient ralentir ou empecher une baisse de diversite du phytoplancton dans les microcosmes durant cette saison. Durant les trois autres saisons, Microcystis predominait, et le pourcentage de cyanobacteries ne variait pas en fonction de la concentration de CO sub(2). Aucune augmentation significative de l'abondance d'un taxon associee a l'augmentation du CO sub(2) durant les experiences en microcosmes in situ n'a ete observee. Traduit par la Redaction
In order to understand the lighting quality effects on the light-adaptive growth of cyanobacteria which does not express phycoerythrin, the thermophilic cyanobacteria PCC6715 in logarithmic growth ...phase was cultured by using white light (control), red light, and blue light with photosynthetically effective photon quantum density (PAR) of 100 pmol/(m2-s). Compared with the growth characteristics of PCC6715 under white light conditions, the changes in the measured and analyzed values of PCC6715 under other light qualities were as follows: the dry weight of PCC6715 significantly increased under blue light and significantly reduced under red light; the red and blue light have different effects on the start time and duration of the photosynthetic pigment synthesis of PCC6715; the maximum light energy conversion efficiency (Fv/Fm) of PCC6715 significantly increased under blue light and decreased significantly under red light; after 6 days of culture, the Fv/Fm of PCC6715 under red and blue light conditions tends to
Toxins produced by cyanobacteria in freshwater ecosystems constitute a serious health risk worldwide for humans that may use the affected water bodies for recreation, drinking water, and/or ...irrigation. Cyanotoxins have also been deemed responsible for loss of animal life in many places around the world. This paper explores the effect of H sub(2)O sub(2) treatments on cyanobacteria and microcystins in natural samples from a hypertrophic reservoir in microcosm experiments. According to the results, cyanobacteria were more easily affected by H sub(2)O sub(2) than by other phytoplanktonic groups. This was shown by the increase in the fractions of chlorophyll-a (a proxy for phytoplankton) and chlorophyll-b (a proxy for green algae) over total phytoplankton pigments and the decrease in the fraction of phycocyanin (a proxy for cyanobacteria) over total phytoplankton pigments. Thus, while an overall increase in phytoplankton occurred, a preferential decrease in cyanobacteria was observed with H sub(2)O sub(2) treatments over a few hours. Moreover, significant degradation of total microcystins was observed under H sub(2)O sub(2) treatments, while more microcystins were degraded when UV radiation was used in combination with H sub(2)O sub(2). The combination of H sub(2)O sub(2) and ultraviolet (UV) treatment in natural samples resulted in total microcystin concentrations that were below the World Health Organization limit for safe consumption of drinking water of 1 mu g/L. Although further investigation into the effects of H sub(2)O sub(2) addition on ecosystem function must be performed, our results show that the application of H sub(2)O sub(2) could be a promising method for the degradation of microcystins in reservoirs and the reduction of public health risks related to the occurrence of harmful algal blooms.
Up and down go the cyanobacteria Ash, C.
Science (American Association for the Advancement of Science),
07/2014, Letnik:
345, Številka:
6193
Journal Article
(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image).Cyanobacteria have evolved a carbon-concentrating mechanism (CCM) which has enabled them to inhabit diverse environments ...encompassing a range of inorganic carbon (C sub(i): ... and CO sub(2)) concentrations. Several uptake systems facilitate inorganic carbon accumulation in the cell, which can in turn be fixed by ribulose 1,5-bisphosphate carboxylase/oxygenase. Here we survey the distribution of genes encoding known C sub(i) uptake systems in cyanobacterial genomes and, using a pfam- and gene context-based approach, identify in the marine (alpha) cyanobacteria a heretofore unrecognized number of putative counterparts to the well-known C sub(i) transporters of beta cyanobacteria. In addition, our analysis shows that there is a huge repertoire of transport systems in cyanobacteria of unknown function, many with homology to characterized C sub(i) transporters. These can be viewed as prospective targets for conversion into ancillary C sub(i) transporters through bioengineering. Increasing intracellular C sub(i) concentration coupled with efforts to increase carbon fixation will be beneficial for the downstream conversion of fixed carbon into value-added products including biofuels. In addition to CCM transporter homologs, we also survey the occurrence of rhodopsin homologs in cyanobacteria, including bacteriorhodopsin, a class of retinal-binding, light-activated proton pumps. Because they are light driven and because of the apparent ease of altering their ion selectivity, we use this as an example of re-purposing an endogenous transporter for the augmentation of C sub(i) uptake by cyanobacteria and potentially chloroplasts.
The search for the ultimate carbon-free fuel has intensified in recent years, with a major focus on photoproduction of H sub(2). Biological sources of H sub(2) include oxygenic photosynthetic green ...algae and cyanobacteria, both of which contain hydrogenase enzymes. Although algal and cyanobacterial hydrogenases perform the same enzymatic reaction through metallo-clusters, their hydrogenases have evolved separately, are expressed differently (transcription of algal hydrogenases is anaerobically induced, while bacterial hydrogenases are constitutively expressed), and display different sensitivity to O sub(2) inactivation. Among various physiological factors, the sensitivity of hydrogenases to O sub(2) has been one of the major factors preventing implementation of biological systems for commercial production of renewable H sub(2). This review addresses recent strategies aimed at engineering increased O sub(2) tolerance into hydrogenases (as of now mainly unsuccessful), as well as towards the development of methods to bypass the O sub(2) sensitivity of hydrogenases (successful but still yielding low solar conversion efficiencies). The author concludes with a description of current approaches from various laboratories to incorporate multiple genetic traits into either algae or cyanobacteria to jointly address limiting factors other than the hydrogenase O sub(2) sensitivity and achieve more sustained H sub(2) photoproduction activity.
Biological soil crusts (BSCs) are small-scale communities of lichens, mosses, algae, and cyanobacteria that cover much of the surface area in regions where vascular plant growth is restricted due to ...harsh environmental conditions, such as perpetually ice-free areas in terrestrial Antarctic environments and alpine areas above the tree line. To our knowledge, none of the available studies provides a direct Antarctic-alpine comparison of BSC activity periods and the water use, both key traits to understand their physiological behavior and therefore related growth and fitness. Here, activity patterns and water relations were studied at two sites, one in continental Antarctica (Garwood Valley 78°S) and one in the High Alps of Austria (Hochtor, Großglockner 2350m). BSCs in continental Antarctica were only rarely active, and if so, then during melt after snowfalls and by fog. In the Austrian Alps, BSCs were continuously active and additionally activated by rainfall, fog, and dew. Consequently, high alpine BSCs can be expected to have much higher photosynthetic productivity supporting higher growth rates than the same functional vegetation unit has in continental Antarctica.
Cyanobacteria possess unique and exciting features among photosynthetic microorganisms for energy conversion applications. This study focuses on production of direct electricity using a ...cyanobacterium called Nostocsp. (NOS) as a photo-biocatalyst immobilized on carbon nanotubes on the anode of photo-bioelectrochemical cells. By illuminating with light (intensity 76 mW cm super(-2)) the NOS immobilized on a carbon nanotube (CNT) modified electrode generated a photocurrent density of 30 mA m super(-2) at 0.2 V (vs.Ag/AgCl). The contribution of different photosynthetic pigments in NOS to the light capture was analyzed and chlorophyll-awas found to be the major contributor to light capture followed by phycocyanin. Further investigation using a set of inhibitors revealed that the electrons were redirected predominantly from PSII to the CNT through the plastoquinone pool and quinol oxidase. A rudimentary design photosynthetic electrochemical cell has been constructed using NOS/CNT on the anode and laccase/CNT on the cathode as catalysts. The cell generated a maximum current density of 250 mA m super(-2) and a peak power density of 35 mW m super(-2) without any mediator. By the addition of 1,4-benzoquinone as a redox mediator, the electricity generation capability was significantly enhanced with a current density of 2300 mA m super(-2) and a power density of 100 mW m super(-2). The power densities achieved in this work are the highest among 'non-engineered' cyanobacteria based electrochemical systems reported to date.
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