Impact of the Iron-Response Regulator Genes on the Release of Iron and Aluminum from Biotite by <i>Rhizobium pusense</i> S41

In this study, the biotite weathering activities of strain S41 and mutants with deletion of the iron response regulator genes <i>fur, rirA,</i> and <i>irr</i> were compared. S41Δ<i>rirA</i> had a 35%–60% increase in Fe and Al concentrations, a 95%–112% increase in siderophore production, and a 18%–22% increase in EPS concentration, while S41Δ<i>irr</i> had a 29%–48% decrease in Fe and Al concentrations and a 32%–42% decrease in siderophore production, compared with strain S41. Under iron-sufficient conditions, S41Δ<i>rirA</i> had a 1.5-fold–2.7-fold increase in siderophore production, while there was similar siderophore production between strain S41 and S41Δ<i>irr</i>. Under iron-limited conditions, S41Δ<i>irr</i> had a 34%–40% decrease in siderophore production compared with strain S41. The expression of genes related to the synthesis of siderophores, iron uptake and transporters, and EPS production in strain S41 significantly increased in iron-limited conditions compared with that in iron-sufficient conditions. The expression of genes associated with the synthesis of siderophores and iron uptake and transporters significantly increased in S41Δ<i>rirA</i> in iron-sufficient and iron-limited conditions but decreased in S41Δ<i>irr</i> in iron-limited conditions. Our results suggested that <i>rirA</i>- and <i>irr</i>-modulated multiple genes may be related to the mineral weathering activities of strain S41.本研究对比了菌株S41以及铁响应调控基因fur、rirA及irr缺失突变体的黑云母（biotite）风化活性。与菌株S41相比，S41ΔrirA的铁与铝浓度提升35%~60%，铁载体（siderophore）产量提升95%~112%，胞外聚合物（extracellular polymeric substances，EPS）浓度提升18%~22%；而S41Δirr的铁与铝浓度降低29%~48%，铁载体产量降低32%~42%。在铁充足条件下，S41ΔrirA的铁载体产量提升1.5~2.7倍，而菌株S41与S41Δirr的铁载体产量相近。在限铁条件下，与菌株S41相比，S41Δirr的铁载体产量降低34%~40%。相较于铁充足条件，菌株S41中与铁载体合成、铁摄取及转运、胞外聚合物生成相关的基因表达量在限铁条件下显著上调。在铁充足及限铁条件下，S41ΔrirA中与铁载体合成、铁摄取及转运相关的基因表达量均显著上调；而在限铁条件下，S41Δirr中上述基因的表达量则显著下调。本研究结果表明，受rirA与irr调控的多个基因可能与菌株S41的矿物风化活性相关。