Siderophore mediated iron acquisition of psychrophilic Antarctic marine bacteria

在南大洋的大片海域，铁是一种高度有限的资源。为了争夺有限且往往局限于局部的铁的流入，细菌开发了各种生化策略来捕获铁并将其输送到细胞中。该项目的目的是提纯和从结构上鉴定细菌产生的铁配体，即所谓的铁载体，这些配体是从不同的南极环境中获得的可培养的嗜冷南极海洋细菌的系统发育谱。一个相应的目标是将这些细菌中不同铁载体对铁的吸收与环境参数(铁胁迫、碳可获得性、盐度和温度)联系起来。通过这种方法，我们将揭开南极细菌所使用的铁结合配体的光谱，并最终有助于更好地了解微生物对南极极端环境的适应。具体地说，从南大洋获得的384个细菌分离株将在反映铁耗竭的生长条件下培养。指示剂分析结合伏安法和质谱仪将用于检测细菌上清液和细胞颗粒中的铁载体。这种方法将使我们能够区分起源于南极的可培养细菌谱系和/或它们的原始栖息地的铁载体类型。我们将通过核磁共振和质谱学从结构上阐明新的铁载体，并提纯这些铁载体和已知的铁载体，作为定量分析和物理化学特性实验测定的参考标准。一个主要目的是描述不同类型的铁载体在代表SO生境的条件下的扩散和吸附特征。我们将研究环境参数(温度、盐度)如何影响每种配体的铁捕获性能和扩散损失。这些一般的铁载体特征将被用来解释测试细菌生长和铁载体产量的实验结果，这些实验依赖于一系列温度、盐度和冰状况。这项研究最终将改进现有的细胞铁吸收模型，增加我们对嗜冷细菌铁吸收策略的了解，并最终有助于更好地理解微生物驱动的南极铁循环的过程，从而解决DFG SPP呼吁的几个中心标准。

Iron is a highly limited resource in large areas of the Southern Ocean. To compete for the limited and often localized influx of iron, bacteria have developed various biochemical strategies to capture iron and transport it into the cell. The aim of this project is to purify and structurally identify bacterially produced iron ligands, so called siderophores, of a phylogenetic spectrum of cultivable psychrophilic Antarctic marine bacteria obtained from divergent Antarctic environments. A consequential objective is then to correlate iron uptake by different siderophores among these bacteria with environmental parameters (iron stress, carbon availability, salinity and temperature). With this approach, we will unravel the spectrum of iron binding ligands used by Antarctic bacteria and ultimately contribute to a better understanding of microbial adaptations to the extreme environments of the SO.Specifically, 384 bacterial isolates obtained from the Southern Ocean will be cultured under growth regimes reflecting iron depletion. Indicator assays in combination with voltammetry and mass spectrometry will be used to detect siderophores in the bacterial supernatants and cell pellets. This approach will allow us to differentiate siderophore types across cultivable bacterial lineages of Antarctic origin and/or their original habitats. We will structurally elucidate novel siderophores by NMR and MS and purify these and known siderophores for reference standards used for quantitative analyses and experimental determination of physicochemical characteristics. One major aim is to characterize diffusion and adsorption traits for different siderophore types under conditions representative of SO habitats. We will study how environmental parameters (temperature, salinity) influence the iron capturing performance and diffusive losses for each ligand type. These general siderophore characteristics will be used to interpret results from experiments testing bacterial growth and siderophore production dependent on a range of temperature, salinity and ice regimes. This study will ultimately improve existing cellular iron uptake models, increase our knowledge of iron uptake strategies of psychrophilic bacteria and ultimately contribute to a better process understanding of the microbially driven Antarctic iron cycle, therefore addressing several of the central criteria of the DFG SPP call.