Collaborative Research: Iron limitation, carbon metabolism and siderophore production in marine bacteria - a systems biology approach

合作研究：海洋细菌中的铁限制、碳代谢和铁载体产生——一种系统生物学方法

• 批准号: 0929203
• 负责人: Elizabeth Mann
• 金额: $ 40.48万
• 依托单位: University of Georgia Research Foundation Inc
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-08-15 至 2013-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0929203&HistoricalAwards=false
• 关键词: Collaborative; Research; Iron; limitation; carbon

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).Iron limitation of heterotrophic bacteria has substantial biogeochemical implications, including lower assimilation efficiencies and reduced incorporation of CO2 into biomass. Marine bacterioplankton also have a large impact on iron speciation in seawater through their production of siderophores, ligands with a high affinity for iron. Over 99.9% of the dissolved iron in seawater is strongly bound to organic ligands, which are likely to include siderophores since they have functional groups and conditional stability constants for iron that are similar to chelators detected in situ. Iron limitation and siderophore synthesis are linked since these ligands are produced specifically in response to low intracellular iron concentrations. Neither process is completely understood in marine bacteria. For instance, the production of iron binding ligands in seawater unexpectedly increases, not decreases when iron is added to HNLC regions. One possible explanation is the role of carbon, which complicates studies of both iron limitation and siderophore synthesis. The extent to which low iron concentrations reduce bacterioplankton growth efficiencies or productivity in situ is not well-quantified because of the rapid stimulation of primary production that occurs after iron limitation of phytoplankton is relieved. The resulting increase in available carbon makes it is difficult to distinguish between direct and indirect iron (i.e. carbon) limitation of marine bacteria. Carbon source and availability may also play a secondary but important role in regulating siderophore production, which can be either stimulated or repressed by the addition of glucose. The objective of this project is to model the interacting gene regulatory networks that control iron acquisition and carbon metabolism in gamma -proteobacteria, specifically Vibrio fischeri. Iron and carbon regulatory pathways are tightly linked in a complex web of relationships mediated by global transcriptional regulators (Fur and CRP) and the small RNA RyhB. In order to construct a gene regulatory network model, the PIs will use an integrated systems biology approach that combines computational, bioinformatics based research and laboratory experimentation. Predictions of gene expression, siderophore production and the flux of iron with changing environmental conditions will be validated by quantifying gene expression using qRT-PCR and global transcriptome analyses, as well as determining iron quotas and iron uptake rates. Intellectual Merit: This study will contribute to the general understanding of iron speciation in the upper ocean by elucidating the interactions between iron and carbon limitation, carbon source and siderophore production. The gene regulatory network model will be capable of identifying environmental variables critical to siderophore production and evaluating potential biomarkers for iron limitation. This project will facilitate the discovery of new genes and control mechanisms involved in iron metabolism and shed light on other processes such as virulence and luminescence, which utilize the same or similar interactions and transcription factors. Finally, this approach also provides a framework for synthesizing information on the genetic level and using it to make predictions about processes such as siderophore production that are ecologically important. Broader Impacts: This project will enhance infrastructure for scientific research and education by mentoring young scientists and supporting both outreach programs and course development at several educational levels. Support is requested for graduate students to participate in the proposed research and all three PIs will recruit undergraduates for summer internships, often targeting underrepresented groups. Research Experiences for Teachers supplements are requested to allow two high school science educators to participate in our research at the Skidaway Institute of Oceanography and design a laboratory exercise that will illustrate how microbes respond to nutrient limitation. The aim is to provide a research experience that will strengthen collaborations among educators at both the local and national levels.

该奖项根据 2009 年美国复苏和再投资法案（公法 111-5）提供资金。异养细菌的铁限制具有重大的生物地球化学影响，包括同化效率较低和二氧化碳与生物质的结合减少。海洋浮游细菌还通过产生铁载体（对铁具有高亲和力的配体）对海水中的铁形态产生很大影响。海水中超过 99.9% 的溶解铁与有机配体牢固结合，有机配体可能包括铁载体，因为它们具有与原位检测到的螯合剂类似的铁官能团和条件稳定常数。铁限制和铁载体合成是相关的，因为这些配体是专门响应细胞内低铁浓度而产生的。对于海洋细菌来说，这两个过程都还没有被完全理解。例如，当将铁添加到 HNLC 区域时，海水中铁结合配体的产量出乎意料地增加，而不是减少。一种可能的解释是碳的作用，这使得铁限制和铁载体合成的研究变得复杂。低铁浓度降低浮游细菌原位生长效率或生产力的程度尚未得到很好的量化，因为浮游植物的铁限制解除后会快速刺激初级生产。由此产生的有效碳增加使得很难区分海洋细菌的直接和间接铁（即碳）限制。碳源和可用性也可能在调节铁载体产生中发挥次要但重要的作用，添加葡萄糖可以刺激或抑制铁载体产生。 该项目的目标是模拟控制γ-变形菌（特别是费氏弧菌）中铁获取和碳代谢的相互作用基因调控网络。铁和碳调节途径在由全局转录调节因子（Fur 和 CRP）和小 RNA RyhB 介导的复杂关系网络中紧密相连。为了构建基因调控网络模型，PI 将使用综合系统生物学方法，结合计算、生物信息学研究和实验室实验。将通过使用 qRT-PCR 和全局转录组分析量化基因表达以及确定铁配额和铁吸收率来验证基因表达、铁载体产量和铁通量随环境条件变化的预测。 智力价值：这项研究将通过阐明铁和碳限制、碳源和铁载体产生之间的相互作用，有助于对上层海洋铁形态的普遍理解。基因调控网络模型将能够识别对铁载体产生至关重要的环境变量，并评估铁限制的潜在生物标志物。该项目将促进发现与铁代谢有关的新基因和控制机制，并揭示利用相同或相似相互作用和转录因子的其他过程，例如毒力和发光。最后，这种方法还提供了一个框架，用于合成遗传水平上的信息，并用它来预测具有生态重要性的铁载体产生等过程。 更广泛的影响：该项目将通过指导年轻科学家并支持多个教育级别的外展计划和课程开发来加强科学研究和教育的基础设施。要求支持研究生参与拟议的研究，所有三位 PI 都将招募本科生进行暑期实习，通常针对代表性不足的群体。要求教师研究经验补充材料允许两名高中科学教育工作者参与我们在斯基德威海洋学研究所的研究，并设计一个实验室练习，以说明微生物如何应对营养限制。目的是提供研究经验，加强地方和国家层面教育工作者之间的合作。