Gene Transfer Agents in the Oceans-What are they doing?

海洋微生物丰富多样。是什么推动了这种多样性？突变和自然选择似乎只占其中的一部分。基因组测序的能力表明，基因的横向转移（LGT），基因在不相关微生物之间的不加区分的移动，在产生多样性中起着重要作用，现在被认为是微生物进化的主要驱动力。在这个项目中，南佛罗里达大学的Paul和McDaniel认为，原核基因转移的三种已知机制（转导、转化和结合）似乎不能也不太可能在海洋环境中以足够的频率发生，从而成为微生物多样性的重要驱动因素。为了研究影响微生物多样性的其他因素，这些研究人员将评估一种新型LGT的重要性，这种LGT涉及鲜为人知的基因转移剂（GTAs）颗粒。gta是特定细菌群（α -变形细菌）基因组中编码的噬菌体样颗粒，可包装宿主基因组DNA的随机片段。这些粒子不会分解它们的宿主，而是将先前宿主的DNA注入新宿主，然后将转移的DNA整合到新宿主的基因组中。基因组测序最近揭示了α -变形细菌基因组中普遍存在GTAs，一项对102个海洋细菌基因组的调查显示，20个（20%）含有假定的GTAs。玫瑰杆菌谱系是一种α -变形菌群，可占沿海环境中细菌的25%，gta的丰富可能使gta成为海洋环境中LGT最重要的机制。这些研究人员想知道：如果gta在细菌基因组中大量存在，它们在做什么？这些研究人员将通过使用已知宿主和已知的遗传示踪剂（如质粒）来检查海洋GTAs的基因转移能力。他们还将通过使用诊断特定gta的标记基因来确定海洋沿海人群中含有gta的细菌的发生率。最后，研究人员将评估gta在海洋细菌本地种群中转移基因的潜力。在这些实验中，这些研究人员将跟踪DNA在实验室菌株和本地细菌之间的运动，然后在本地细菌种群之间的运动，以估计海洋中gta基因转移的自然速率。Paul和McDaniel这项研究的长期目标是阐明一种鲜为人知的LGT形式在海洋环境中的作用，为后续研究通过gta进行的基因通量和控制海洋微生物多样性的因素奠定基础。作为这个项目的一部分，私人机构将开展一些外联活动。她们将开发关于GTA指标的高中实验模块，并将在佛罗里达州皮内拉斯县多种族学校的课堂上使用这些模块。她们将继续参加海洋学女孩夏令营，这是一个每年夏天为期三周的夏令营，由USF海洋科学学院主办，面向九年级的学生。pi计划将GTAs检测器组件添加到这些实验室活动中。

Marine microorganisms are abundant and diverse. What drives this diversity? Mutation and natural selection appear to account for only a portion of it. The ability to sequence genomes is demonstrating that lateral gene transfer (LGT), the indiscriminant movement of genes between unrelated microbes, plays a significant role in generating diversity, and it is now recognized as a major driving force in microbial evolution. In this project, Paul and McDaniel of the University of South Florida argue that the three known mechanisms of prokaryotic gene transfer (transduction, transformation, and conjugation) appear to be unable and unlikely to occur with sufficient frequency in the marine environment to be significant drivers of microbial diversity. In order to examine other factors contributing to microbial diversity, these investigators will be evaluating the significance of a novel form of LGT which involves little-understood particles called Gene Transfer Agents (GTAs). GTAs are phage-like particles encoded in the genomes of particular groups of bacteria (alpha-proteobacteria) that package random fragments of host genomic DNA. These particles do not lyse their host, but rather inject their prior host's DNA into a new host, and the transferred DNA then integrates into the new host's genome. Genomic sequencing has recently revealed the prevalence of GTAs in alpha-proteobacterial genomes, and a survey of 102 marine bacterial genomes indicated twenty (20%) contained putative GTAs. The abundance of GTAs in the Roseobacter lineage, an alpha-proteobacteria group that can comprise up to 25% of the bacteria in coastal environments, may make GTAs the most important mechanism of LGT in the marine environment. These researchers want to know: if GTAs are abundant in bacterial genomes, what are they doing? These investigators will be examining the gene transfer capability of marine GTAs by using known hosts and known genetic tracers, like plasmids. They will also determine the occurrence of GTA-containing bacteria in marine coastal populations by using marker genes diagnostic for specific GTAs. Finally, the investigators will evaluate the potential for GTAs to transfer genes within indigenous populations of marine bacteria. In these experiments, these investigators will track the movement of DNA between lab strains and indigenous bacteria and then between populations of indigenous bacteria to estimate the natural rate of gene transfer by GTAs in the ocean. The longterm goal of this research by Paul and McDaniel is to elucidate the role of a little understood form of LGT in the marine environment, setting the stage for follow on studies on the flux of genes via GTAs and on what controls microbial diversity in the oceans. The PIs will carry out a number of outreach activities as a part of this project. They will be developing high school lab modules on GTA indicators and will be using them in classes from ethnically and racially diverse schools in Pinellas County, FL. They will continue their participation in the Oceanography Camp for Girls, a three week day camp each summer, hosted by the USF College of Marine Science, for students entering the 9th grade. THe PIs plan to add a GTAs detector component to these lab activities.