scholarly journals Silica burial enhanced by iron limitation in oceanic upwelling margins

2014 ◽  
Vol 7 (7) ◽  
pp. 541-546 ◽  
Author(s):  
L. E. Pichevin ◽  
R. S. Ganeshram ◽  
W. Geibert ◽  
R. Thunell ◽  
R. Hinton
Keyword(s):  
Iron Limitation ◽  
Oceanic Upwelling

Effect of Iron Limitation on the Ultrastructure of Agmenellum Quadruplicatum

1981 ◽  
Vol 39 ◽  
pp. 410-411
Author(s):  
L. P. Hardie ◽  
D. L. Balkwill ◽  
S. E. Stevens
Keyword(s):  
Growth Medium ◽  
Green Alga ◽  
Natural Habitat ◽  
Iron Limitation ◽  
Natural Environments ◽  
Blue Green Alga ◽  
Marine Cyanobacterium ◽  
Natural Systems ◽  
Thin Sectioning ◽  
Agmenellum Quadruplicatum

Agmenellum quadruplicatum is a unicellular, non-nitrogen-fixing, marine cyanobacterium (blue-green alga). The ultrastructure of this organism, when grown in the laboratory with all necessary nutrients, has been characterized thoroughly. In contrast, little is known of its ultrastructure in the specific nutrient-limiting conditions typical of its natural habitat. Iron is one of the nutrients likely to limit this organism in such natural environments. It is also of great importance metabolically, being required for both photosynthesis and assimilation of nitrate. The purpose of this study was to assess the effects (if any) of iron limitation on the ultrastructure of A. quadruplicatum. It was part of a broader endeavor to elucidate the ultrastructure of cyanobacteria in natural systemsActively growing cells were placed in a growth medium containing 1% of its usual iron. The cultures were then sampled periodically for 10 days and prepared for thin sectioning TEM to assess the effects of iron limitation.

scholarly journals Tailoring a Global Iron Regulon to a Uropathogen

mBio ◽  
2020 ◽  
Vol 11 (2) ◽  
Author(s):  
Rajdeep Banerjee ◽  
Erin Weisenhorn ◽  
Kevin J. Schwartz ◽  
Kevin S. Myers ◽  
Jeremy D. Glasner ◽  
...  
Keyword(s):  
Amino Acids ◽  
Urinary Tract ◽  
Amino Acid ◽  
Regulatory Network ◽  
Iron Homeostasis ◽  
Iron Limitation ◽  
Content Type ◽  
E Coli ◽  
General Stress ◽  
K 12

ABSTRACT Pathogenicity islands and plasmids bear genes for pathogenesis of various Escherichia coli pathotypes. Although there is a basic understanding of the contribution of these virulence factors to disease, less is known about variation in regulatory networks in determining disease phenotypes. Here, we dissected a regulatory network directed by the conserved iron homeostasis regulator, ferric uptake regulator (Fur), in uropathogenic E. coli (UPEC) strain CFT073. Comparing anaerobic genome-scale Fur DNA binding with Fur-dependent transcript expression and protein levels of the uropathogen to that of commensal E. coli K-12 strain MG1655 showed that the Fur regulon of the core genome is conserved but also includes genes within the pathogenicity/genetic islands. Unexpectedly, regulons indicative of amino acid limitation and the general stress response were also indirectly activated in the uropathogen fur mutant, suggesting that induction of the Fur regulon increases amino acid demand. Using RpoS levels as a proxy, addition of amino acids mitigated the stress. In addition, iron chelation increased RpoS to the same levels as in the fur mutant. The increased amino acid demand of the fur mutant or iron chelated cells was exacerbated by aerobic conditions, which could be partly explained by the O2-dependent synthesis of the siderophore aerobactin, encoded by an operon within a pathogenicity island. Taken together, these data suggest that in the iron-poor environment of the urinary tract, amino acid availability could play a role in the proliferation of this uropathogen, particularly if there is sufficient O2 to produce aerobactin. IMPORTANCE Host iron restriction is a common mechanism for limiting the growth of pathogens. We compared the regulatory network controlled by Fur in uropathogenic E. coli (UPEC) to that of nonpathogenic E. coli K-12 to uncover strategies that pathogenic bacteria use to overcome iron limitation. Although iron homeostasis functions were regulated by Fur in the uropathogen as expected, a surprising finding was the activation of the stringent and general stress responses in the uropathogen fur mutant, which was rescued by amino acid addition. This coordinated global response could be important in controlling growth and survival under nutrient-limiting conditions and during transitions from the nutrient-rich environment of the lower gastrointestinal (GI) tract to the more restrictive environment of the urinary tract. The coupling of the response of iron limitation to increased demand for amino acids could be a critical attribute that sets UPEC apart from other E. coli pathotypes.

scholarly journals The Fish Pathogen Vibrio ordalii Under Iron Deprivation Produces the Siderophore Piscibactin

2019 ◽  
Vol 7 (9) ◽  
pp. 313 ◽  
Author(s):  
Pamela Ruiz ◽  
Miguel Balado ◽  
Juan Carlos Fuentes-Monteverde ◽  
Alicia E. Toranzo ◽  
Jaime Rodríguez ◽  
...  
Keyword(s):  
Gene Cluster ◽  
Iron Uptake ◽  
Peptide Mass Fingerprinting ◽  
Iron Limitation ◽  
Fish Pathogen ◽  
Fish Pathogens ◽  
Iron Deprivation ◽  
Peptide Mass ◽  
Photobacterium Damselae ◽  
Vibrio Ordalii

Vibrio ordalii is the causative agent of vibriosis, mainly in salmonid fishes, and its virulence mechanisms are still not completely understood. In previous works we demonstrated that V. ordalii possess several iron uptake mechanisms based on heme utilization and siderophore production. The aim of the present work was to confirm the production and utilization of piscibactin as a siderophore by V. ordalii. Using genetic analysis, identification by peptide mass fingerprinting (PMF) of iron-regulated membrane proteins and chemical identification by LC-HRMS, we were able to clearly demonstrate that V. ordalii produces piscibactin under iron limitation. The synthesis and transport of this siderophore is encoded by a chromosomal gene cluster homologous to another one described in V. anguillarum, which also encodes the synthesis of piscibactin. Using β-galactosidase assays we were able to show that two potential promoters regulated by iron control the transcription of this gene cluster in V. ordalii. Moreover, biosynthetic and transport proteins corresponding to piscibactin synthesis and uptake could be identified in membrane fractions of V. ordalii cells grown under iron limitation. The synthesis of piscibactin was previously reported in other fish pathogens like Photobacterium damselae subsp. piscicida and V. anguillarum, which highlights the importance of this siderophore as a key virulence factor in Vibrionaceae bacteria infecting poikilothermic animals.

Guadalupian cool versus warm water deposits in central Iran: a record of the Capitanian Kamura event

2017 ◽  
Vol 156 (3) ◽  
pp. 430-446 ◽  
Author(s):  
SAKINEH AREFIFARD
Keyword(s):  
Primary Productivity ◽  
Association Studies ◽  
Central Iran ◽  
Warm Water ◽  
Middle Permian ◽  
Warm Climate ◽  
Diagenetic Alteration ◽  
Lime Mud ◽  
Jamal Formation ◽  
Oceanic Upwelling

AbstractAn integration of geochemical and grain association studies were carried out on Middle Permian deposits in central Iran where both cool and warm water carbonates are found. The recrystallization of most bioclasts, lime-mud matrix and ooids along with high Sr contents suggests a probable original aragonite mineralogy for carbonates of the Middle Permian Jamal Formation at the Shotori section. Low bulk carbonate δ18O values imply pervasive diagenetic alteration in this section. Conversely, Middle Permian deposits at the correlative Bagh-e Vang section have a probable calcite precursor supported by low Sr contents and no evidence of recrystallization. This mineralogical variation in these coeval carbonates is considered to be due to the change in depth and temperature of the depositional palaeoenvironment. δ13C values started to rise over 2 ‰ PDB and reached a maximum of 4.3 ‰ PDB at the Wordian–Capitanian boundary at the Bagh-e Vang section. This δ13C rise is attributed to high primary productivity as previously reported in the Capitanian Abadeh Formation in central Iran. The positive δ13C excursion in these sections is correlated with the Capitanian ‘Kamura event’ identified from the mid-Panthalassian sections in Japan. No noticeable positive excursion occurs in the δ13C plot at the Shotori section making the interpretation of palaeo-productivity difficult. It is suggested that an active oceanic upwelling was the probable driver of the Middle Permian oceanic productivity in central Iran. Remarkable negative δ13C excursions around 3.7 and 4.2 ‰ PDB in Capitanian carbonates close to the Guadalupian–Lopingian boundary at the Bagh-e Vang and Abadeh sections, respectively are recorded, which are a proxy for low palaeo-productivity and a transition from a cool to warm climate, consistent with an early Lopingian sea level rise.

scholarly journals Macronutrient and iron limitation of phytoplankton growth in Hong Kong coastal waters

2006 ◽  
Vol 318 ◽  
pp. 141-152 ◽  
Author(s):  
AJ Miao ◽  
DA Hutchins ◽  
K Yin ◽  
FX Fu ◽  
PJ Harrison ◽  
...  
Keyword(s):  
Hong Kong ◽  
Coastal Waters ◽  
Phytoplankton Growth ◽  
Iron Limitation ◽  
Hong Kong Coastal Waters

scholarly journals Iron Requirement for Mn(II) Oxidation by Leptothrix discophora SS-1

2008 ◽  
Vol 75 (5) ◽  
pp. 1229-1235 ◽  
Author(s):  
Iman A. El Gheriany ◽  
Daniela Bocioaga ◽  
Anthony G. Hay ◽  
William C. Ghiorse ◽  
Michael L. Shuler ◽  
...  
Keyword(s):  
Complex Formation ◽  
Temporal Variations ◽  
Iron Limitation ◽  
Gene Transcript ◽  
Cellular Functions ◽  
Transcript Levels ◽  
Leptothrix Discophora ◽  
Geochemical Cycling ◽  
Iron Requirement

ABSTRACT A common form of biocatalysis of Mn(II) oxidation results in the formation of biogenic Mn(III, IV) oxides and is a key reaction in the geochemical cycling of Mn. In this study, we grew the model Mn(II)-oxidizing bacterium Leptothrix discophora SS-1 in media with limited iron (0.1 μM iron/5.8 mM pyruvate) and sufficient iron (0.2 μM iron/5.8 mM pyruvate). The influence of iron on the rate of extracellular Mn(II) oxidation was evaluated. Cultures in which cell growth was limited by iron exhibited reduced abilities to oxidize Mn(II) compared to cultures in medium with sufficient iron. While the extracellular Mn(II)-oxidizing factor (MOF) is thought to be a putative multicopper oxidase, Mn(II) oxidation in the presence of zero added Cu(II) was detected and the decrease in the observed Mn(II) oxidation rate in iron-limited cultures was not relieved when the medium was supplemented with Cu(II). The decline of Mn(II) oxidation under iron-limited conditions was not accompanied by siderophore production and is unlikely to be an artifact of siderophore complex formation with Mn(III). The temporal variations in mofA gene transcript levels under conditions of limited and abundant iron were similar, indicating that iron limitation did not interfere with the transcription of the mofA gene. Our quantitative PCR results provide a step forward in understanding the regulation of Mn(II) oxidation. The mechanistic role of iron in Mn(II) oxidation is uncertain; the data are consistent with a direct requirement for iron as a component of the MOF or an indirect effect of iron resulting from the limitation of one of many cellular functions requiring iron.

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