Figure - PMC

Skip to main content

An official website of the United States government

Here's how you know

Here's how you know

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

View full-text article in PMC

. 2021 Apr 6;12:2069. doi: 10.1038/s41467-021-22258-1

Search in PMC
Search in PubMed
View in NLM Catalog
Add to search

© The Author(s) 2021

Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/.

PMC Copyright notice

Fig. 3 — Both species were cultured in an open-culture system (a, b) and the oxidation of Fe(II) monitored (c, d). Chl a growth curves (a) and doubling times (b) of the cultures in an anoxic open-culture system with a recurring nightly addition of 140 µM Fe(II). For the first 12 days during every dark cycle, the cultures were shaken briefly to release the dissolved oxygen and Fe(II) solution was added to a total concentration of 120–140 µM. Chl a measurements (a) were taken every 2nd to 3rd day for 19 days. Cultures grown without Fe(II) addition were used as controls (solid line). Cell doubling times during the exponential growth (b) were determined from day 2 to 12 for both strains. The retention of Fe(II) during the dark cycle (d) was exemplary tested in analogous 7-day old, exponentially growing control cultures of Pseudanabaena sp. PCC7367 (green) and Synechococcus PCC7336 (orange) by measuring the Fe(II) concentration (dashed lines), while in parallel recording the oxygen concentration (solid line). The Fe(II) oxidation was measured every 10 min with a spectrophotometric ferrozine assay. Two hours after the start of the light cycle, the amount of Fe(III) in the media was assessed (open squares). The average rate of Fe(II) oxidation per Chl a during the light cycle (c) was calculated and compared to cultures which were additionally stirred at constant 250 rpm on a magnetic stirrer. Data are presented as mean values ± SD with n = 4 biologically independent samples, except for the stirred Fe(II) oxidation rate with n = 2 biologically independent samples. Asterisks (^*) represent a significant difference between Fe(II) supplemented culture and control (p < 0.05, Student’s t-test, two-tailed).