INVESTIGATIONS OF THE ROLE OF IRON IN CHLOROPHYLL METABOLISM

Logo of plntphys Plant Physiol. 1963 Nov; 38(6): 632–638. PMCID: PMC549987 Investigations of the Role of Iron in Chlorophyll Metabolism I. Effect of Iron Deficiency on Chlorophyll and Heme Content and on the Activities of Certain Enzymes in Leaves 1,2 H. V. Marsh, Jr.,3 H. J. Evans,4 and G. Matrone Author information ► Copyright and License information ► This article has been cited by other articles in PMC. Full text Full text is available as a scanned copy of the original print version. Get a printable copy (PDF file) of the complete article (1.1M), or click on a page image below to browse page by page. Links to PubMed are also available for Selected References.

BANDEIRA DE PAZ

Logo lhe haviam de ter calhado fotografias com povoações. E,assim,não teve outro remédio se não assaltar quintais,fazer rasgões na vestimenta em arame farpado,afrontar o ladrar e a dentuça de cães de todas as raças,passar por intruso,aqui e ali,fartar-se de dar explicações do porquê de entrar em casa alheia. Pode dizer-se que teve muita sorte,pois podiam tê-lo tomado como salteador de estrada,e afrontá-lo de arma pronta para disparar. Deve-lhe ter valido o ter andado de bandeira de paz sempre hasteada,que era,afinal,o seu ar de não fazer mal a uma mosca. Só uma vez foi confrontado à má fé,o que não é nada mau,quando tanto caminho palmilhou. Uma mágoa,porém,carrega. É que podia ter perturbado a inspiração de um grande compositor. Era a ignorância. Sabia lá ele que naquela casa residia tal personalidade? As fotografias só davam conta do que estava à vista. Mas,talvez,daqui a algum tempo isso seja possível. Quem sabe?

AR DE MAU

Passa os dias encostado às paredes,conversando com os amigos,ou aos balcões das tabernas junto ao mercado. A idade também já não dá para muito mais. Pois há uns dias mudou de vida. Foi arvorado em guarda de um prédio em construção. Assumiu compenetradamente o seu papel. Ali gastava as horas,de manhã à noite,vigiando. A sua voz até parece que engrossou. Ficou com ar de patrão. O construtor fazia mesmo uma fraca figura ao seu lado. O homem é alto,a cara mete respeito,o boné descai-lhe para os olhos,em jeito de rufia de bairro. Nenhum carro,por pouco tempo que fosse,podia estacionar perto da obra. Logo ele aparecia,com ar de mau,a mandar avançar. Para melhor observação,colocava-se no passeio,no outro lado da rua,acompanhando as diferentes fases ,com olhos de que aquilo era seu. Julga-se até que lá dormiu. Continuou,por ocasião da venda,a permanecer nas imediações,e mesmo depois de tudo transacionado. Fora ali que pontificara meses a fio. Não o esqueceria nunca e sentir-se-ia muito agradecido pela confiança nele depositada. Ronda-o,agora,amorosamente. Dá a impressão de ser um filho seu. Vira-o nascer,crescer e tornar-se num bonito prédio. Amparara-o. Estará ciente de que dele se desprende alguma coisa de si. E dali não sai. Encosta-se aos carros estacionados e assiste ao movimento da loja do rez-do-chão. Fora uma ama inexcedível. O boné continua descaído,olhando para todos os lados,zelando.

MICROBIAL SIDEROPHORES AND THEIR POTENTIAL APPLICATION: A REVIEW

Microbial siderophores and their potential applications: a review. Saha M1, Sarkar S1, Sarkar B2, Sharma BK3, Bhattacharjee S4, Tribedi P5. Author information Abstract Siderophores are small organic molecules produced by microorganisms under iron-limiting conditions which enhance the uptake of iron to the microorganisms. In environment, the ferric form of iron is insoluble and inaccessible at physiological pH (7.35-7.40). Under this condition, microorganisms synthesize siderophores which have high affinity for ferric iron. These ferric iron-siderophore complexes are then transported to cytosol. In cytosol, the ferric iron gets reduced into ferrous iron and becomes accessible to microorganism. In recent times, siderophores have drawn much attention due to its potential roles in different fields. Siderophores have application in microbial ecology to enhance the growth of several unculturable microorganisms and can alter the microbial communities. In the field of agriculture, different types of siderophores promote the growth of several plant species and increase their yield by enhancing the Fe uptake to plants. Siderophores acts as a potential biocontrol agent against harmful phyto-pathogens and holds the ability to substitute hazardous pesticides. Heavy-metal-contaminated samples can be detoxified by applying siderophores, which explicate its role in bioremediation. Siderophores can detect the iron content in different environments, exhibiting its role as a biosensor. In the medical field, siderophore uses the "Trojan horse strategy" to form complexes with antibiotics and helps in the selective delivery of antibiotics to the antibiotic-resistant bacteria. Certain iron overload diseases for example sickle cell anemia can be treated with the help of siderophores. Other medical applications of siderophores include antimalarial activity, removal of transuranic elements from the body, and anticancer activity. The aim of this review is to discuss the important roles and applications of siderophores in different sectors including ecology, agriculture, bioremediation, biosensor, and medicine.

SIDERÓFOROS

A água do mar é alcalina,com um pH à volta de 8. Quer isto dizer,entre outras coisas,que é muito pobre em ferro,o que pode trazer problemas a vidas que dele necessitem,como o plâncton. Mas a natureza é sábia,pelo que há uns microorganismos que segregam agentes quelatizantes específicos para o ferro,os sideróforos(siderophores),que se desenvolvem em ambientes pobres em ferro. Eles,os sideróforos,lá vão fazer disponível um elemento que há em abundância na Terra,mas que nem sempre está disposto a ser comido.

ATMOSPHERIC GLOBAL DUST CYCLE AND IRON INPUTS TO THE OCEAN

Explore this journal > Global Biogeochemical Cycles Previous article in issue: Empirical and mechanistic models for the particle export ratio Next article in issue: Reliability of N flux rates estimated from 15N enrichment and dilution experiments in aquatic systems View issue TOC Volume 19, Issue 4 December 2005 Atmospheric global dust cycle and iron inputs to the ocean Authors Natalie M. Mahowald, Alex R. Baker, Gilles Bergametti, Nick Brooks, Robert A. Duce, Timothy D. Jickells, Nilgün Kubilay, Joseph M. Prospero, Ina Tegen First published: 30 December 2005Full publication history DOI: 10.1029/2004GB002402View/save citation Cited by: 301 articles Citation tools Abstract [1] Since iron is an important micronutrient, deposition of iron in mineral aerosols can impact the carbon cycle and atmospheric CO2. This paper reviews our current understanding of the global dust cycle and identifies future research needs. The global distribution of desert dust is estimated from a combination of observations of dust from in situ concentration, optical depth, and deposition data; observations from satellite; and global atmospheric models. The anthropogenically influenced portion of atmospheric desert dust flux is thought to be smaller than the natural portion, but is difficult to quantify due to the poorly understood response of desert dust to changes in climate, land use, and water use. The iron content of aerosols is thought to vary by a factor of 2, while the uncertainty in dust deposition is at least a factor of 10 in some regions due to the high spatial and temporal variability and limited observations. Importantly, we have a limited understanding of the processes by which relatively insoluble soil iron (typically ∼0.5% is soluble) becomes more soluble (1–80%) during atmospheric transport, but these processes could be impacted by anthropogenic emissions of sulfur or organic acids. In order to understand how humans will impact future iron deposition to the oceans, we need to improve our understanding of: iron deposition to remote oceans, iron chemistry in aerosols, how desert dust sources will respond to climate change, and how humans will impact the transport of bioavailable fraction of iron to the oceans.

IRON,PHYTOPLANKTON GROWTH,AND THE CARBON CYCLE

Met Ions Biol Syst. 2005;43:153-93. Iron, phytoplankton growth, and the carbon cycle. Street JH1, Paytan A. Author information Abstract Iron is an essential nutrient for all living organisms. Iron is required for the synthesis of chlorophyll and of several photosynthetic electron transport proteins and for the reduction of CO2, SO4(2-), and NO3(-) during the photosynthetic production of organic compounds. Iron concentrations in vast areas of the ocean are very low (<1 nM) due to the low solubility of iron in oxic seawater. Low iron concentrations have been shown to limit primary production rates, biomass accumulation, and ecosystem structure in a variety of open-ocean environments, including the equatorial Pacific, the subarctic Pacific and the Southern Ocean and even in some coastal areas. Oceanic primary production, the transfer of carbon dioxide into organic carbon by photosynthetic plankton (phytoplankton), is one process by which atmospheric CO2 can be transferred to the deep ocean and sequestered for long periods of time. Accordingly, iron limitation of primary producers likely plays a major role in the global carbon cycle. It has been suggested that variations in oceanic primary productivity, spurred by changes in the deposition of iron in atmospheric dust, control atmospheric CO2 concentrations, and hence global climate, over glacial-interglacial timescales. A contemporary application of this "iron hypothesis" promotes the large-scale iron fertilization of ocean regions as a means of enhancing the ability of the ocean to store anthropogenic CO2 and mitigate 21st century climate change. Recent in situ iron enrichment experiments in the HNLC regions, however, cast doubt on the efficacy and advisability of iron fertilization schemes. The experiments have confirmed the role of iron in regulating primary productivity, but resulted in only small carbon export fluxes to the depths necessary for long-term sequestration. Above all, these experiments and other studies of iron biogeochemistry over the last two decades have begun to illustrate the great complexity of the ocean system. Attempts to engineer this system are likely to provoke a similarly complex, unpredictable response.