An Exploration of Siderophore Production in Bacterial Isolates from Icelandic Hot Springs

Abstract

Thermophilic microorganisms represent a promising but underexplored source of thermostable siderophores — iron-chelating metabolites with potential applications in bioremediation, agriculture, and medicine. This study investigated three thermophilic bacterial strains isolated from Icelandic hot springs for their ability to produce siderophores under iron-limited conditions. Fermentations were carried out at 60–65°C in media with varied iron availability, including supplementation with 100 μM 2,2’-dipyridyl (DIP) to induce iron stress. Growth
was monitored spectrophotometrically, and siderophore production was assessed using a panel of chemical assays, including the Chrome Azurol S (CAS) test and class-specific detection methods (Arnow, Rioux, Csaky, Atkin, and Tetrazolium). Statistical significance was determined at α = 0.05.

Strain 4624 demonstrated robust growth and produced significant quantities of catecholate siderophores in DIP medium, with strong signals observed in both Arnow (p < 0.001) and Rioux assays. Hydroxamate production was also suggested by Csaky results (p = 0.044), though assay instability warrants caution. In contrast, strain 7349 showed only weak trends toward hydroxamate activity, while strain 623 exhibited neither siderophore production nor growth resilience under iron stress. Partial purification of catecholates from strain 4624 using XAD-2 resin confirmed enrichment, though recovery was limited due to early saturation.

These findings validate earlier genomic predictions and highlight the potential of geothermal bacteria, particularly strain 4624, as sources of siderophores operable at high temperatures. Further optimisation of culture conditions and downstream purification could advance their use in industrial or environmental applications.

Popular Abstract

Could bacteria from Iceland’s hot springs help us recover metals or fight infections? Maybe, if we can unlock their secret survival tools.

Iron is essential to almost all life, but in nature, it’s not always easy to come by. To get around this, many bacteria produce special molecules called siderophores — tiny, iron-grabbing tools that help them scavenge what they need. These molecules can bind iron even in extremely low concentrations, making them interesting not only from a biological perspective but also for industrial and environmental applications. They could, for example, help clean up metal-contaminated sites or be repurposed in medicine to target harmful bacteria.

In this project, I studied whether certain heat-loving bacteria, isolated from Icelandic hot springs, produce siderophores when starved of iron. These bacteria thrive at high temperatures where ordinary microbes can’t survive, meaning any useful compounds they produce might be more stable and suitable for demanding industrial processes.

Out of the three strains tested, one stood out. Known as strain 4624, it produced a type of siderophore called a catecholate when iron was made scarce. These are especially powerful iron-binders, also found in some of the most aggressive pathogens. Using chemical tests and a mild purification process, I was able to show that these molecules were released during the bacteria’s growth, and at temperatures around 60°C. That’s like running a factory process in a sauna. Another strain (7349) may have made a different type of siderophore, but the results weren’t as clear. The third strain (623) didn’t appear to make any at all under the tested conditions.

These findings matter because they show that bacteria from Iceland’s geothermal environments don’t just survive in extreme conditions, but they might produce useful molecules while they’re at it. That could open the door for future work on sustainable biotechnologies, like eco-friendly ways to extract metals or improve crop protection. The results are early, and more work is needed to fully understand and harness these siderophores, including optimising how they’re produced and purified. But this study is a small step toward turning volcanic microbes into future problem-solvers

• author: Grøntveit Tverå, Emilie
• supervisor: Roya Rezaei
• organization: Biotechnology (MSc); Biotechnology (M.Sc.Eng.)
• course: KBTM01 20251
• year: 2025
• type: H2 - Master's Degree (Two Years)
• subject: Biology and Life Sciences
• keywords: siderophores, geothermal, thermophiles, catecholates, hydroxamates, iron, fermentation, biotechnology
• language: English
• id: 9201337
• date added to LUP: 2025-08-18 10:27:44
• date last changed: 2025-08-18 10:27:44