Work

Sudden anaerobization in Amphibacillus xylanus increases intracellular labile ferrous iron and inhibits cell growth

Year: 2026

Type: article

Abstract: Amphibacillus xylanus is an aerotolerant anaerobe that consumes large amounts of oxygen and requires iron as an essential micronutrient during its aerobic growth. However, this bacterium lacks a typical respiratory chain; therefore, intracellular free flavins and their reductases are thought to participate in the reduction of molecular oxygen and ferric iron (Fe 3+ ). This system can potentially generate hydroxyl radicals through the Fenton reaction, highlighting the importance of regulating the production of redox‐active ferrous iron (Fe 2+ ). In this study, we employed a strategy of abruptly switching the cell culture system from aerobic to anaerobic conditions to examine Fe 2+ production via free flavins. Sudden anaerobization induced growth inhibition and a significant increase in intracellular labile Fe 2+ . Whole‐cell 57 Fe Mössbauer spectroscopy revealed that in aerobic cells, high‐spin Fe 3+ is the major chemical species, whereas in anaerobic conditions, the intracellular iron pool is completely converted into Fe 2+ and consists of low‐ and high‐spin Fe 2+ species. Increased Fe 2+ production was mimicked using cell‐free extracts and the reductase activity promoted electron transfer from NADH to Fe 3+ via physiological concentrations of free flavin adenine dinucleotide under anaerobic conditions. RNA sequencing showed that the electrons of NADH generated through glycolysis and the pyruvate metabolic pathway can flow into a flavoprotein with flavin reductase activity. These findings suggest that the production of labile Fe 2+ via free flavin is regulated by molecular oxygen, allowing safe iron utilization during the aerobic growth of A. xylanus .

Source: FEBS Open Bio

DOI: 10.1002/2211-5463.70255