Durham Bryndan P, Dearth Stephen P, Sharma Shalabh, Amin Shady A, Smith Christa B, Campagna Shawn R, Armbrust E Virginia, Moran Mary Ann
Department of Microbiology, University of Georgia, Athens, GA, USA.
Department of Chemistry, University of Tennessee, Knoxville, TN, USA.
Environ Microbiol. 2017 Sep;19(9):3500-3513. doi: 10.1111/1462-2920.13834. Epub 2017 Jul 21.
The trophic linkage between marine bacteria and phytoplankton in the surface ocean is a key step in the global carbon cycle, with almost half of marine primary production transformed by heterotrophic bacterioplankton within hours to weeks of fixation. Early studies conceptualized this link as the passive addition and removal of organic compounds from a shared seawater reservoir. Here, we analysed transcript and intracellular metabolite patterns in a two-member model system and found that the presence of a heterotrophic bacterium induced a potential recognition cascade in a marine phytoplankton species that parallels better-understood vascular plant response systems. Bacterium Ruegeria pomeroyi DSS-3 triggered differential expression of >80 genes in diatom Thalassiosira pseudonana CCMP1335 that are homologs to those used by plants to recognize external stimuli, including proteins putatively involved in leucine-rich repeat recognition activity, second messenger production and protein kinase cascades. Co-cultured diatoms also downregulated lipid biosynthesis genes and upregulated chitin metabolism genes. From differential expression of bacterial transporter systems, we hypothesize that nine diatom metabolites supported the majority of bacterial growth, among them sulfonates, sugar derivatives and organic nitrogen compounds. Similar recognition responses and metabolic linkages as observed in this model system may influence carbon transformations by ocean plankton.
海洋表层中海洋细菌与浮游植物之间的营养联系是全球碳循环中的关键一步，几乎一半的海洋初级生产在固定后的数小时至数周内被异养浮游细菌转化。早期研究将这种联系概念化为从共享海水库中被动添加和去除有机化合物。在这里，我们分析了一个二元模型系统中的转录本和细胞内代谢物模式，发现异养细菌的存在会在一种海洋浮游植物物种中引发潜在的识别级联反应，这与人们更了解的维管植物反应系统类似。鲁杰氏菌属的波默罗伊氏菌DSS-3触发了硅藻假微型海链藻CCMP1335中80多个基因的差异表达，这些基因与植物用于识别外部刺激的基因同源，包括可能参与富含亮氨酸重复识别活性、第二信使产生和蛋白激酶级联反应的蛋白质。共培养的硅藻还下调了脂质生物合成基因并上调了几丁质代谢基因。从细菌转运系统的差异表达来看，我们推测九种硅藻代谢物支持了大部分细菌生长，其中包括磺酸盐、糖衍生物和有机氮化合物。在这个模型系统中观察到的类似识别反应和代谢联系可能会影响海洋浮游生物的碳转化。
