Barreto Filho Marcelo Malisano, Lu Zhiying, Walker Melissa, Morris J Jeffrey
University of Alabama at Birmingham Department of Biology, 1300 University Blvd CH464, Birmingham, AL, 35294, USA.
ISME Commun. 2022 Nov 15;2(1):113. doi: 10.1038/s43705-022-00197-2.
Many microbial photoautotrophs depend on heterotrophic bacteria for accomplishing essential functions. Environmental changes, however, could alter or eliminate such interactions. We investigated the effects of changing pCO on gene transcription in co-cultures of 3 strains of picocyanobacteria (Synechococcus strains CC9311 and WH8102 and Prochlorococcus strain MIT9312) paired with the 'helper' bacterium Alteromonas macleodii EZ55. Co-culture with cyanobacteria resulted in a much higher number of up- and down-regulated genes in EZ55 than pCO by itself. Pathway analysis revealed significantly different transcription of genes involved in carbohydrate metabolism, stress response, and chemotaxis, with different patterns of up- or down-regulation in co-culture with different cyanobacterial strains. Gene transcription patterns of organic and inorganic nutrient transporter and catabolism genes in EZ55 suggested resources available in the culture media were altered under elevated (800 ppm) pCO conditions. Altogether, changing transcription patterns were consistent with the possibility that the composition of cyanobacterial excretions changed under the two pCO regimes, causing extensive ecophysiological changes in both members of the co-cultures. Additionally, significant downregulation of oxidative stress genes in MIT9312/EZ55 cocultures at 800 ppm pCO were consistent with a link between the predicted reduced availability of photorespiratory byproducts (i.e., glycolate/2PG) under this condition and observed reductions in internal oxidative stress loads for EZ55, providing a possible explanation for the previously observed lack of "help" provided by EZ55 to MIT9312 under elevated pCO. If similar broad alterations in microbial ecophysiology occur in the ocean as atmospheric pCO increases, they could lead to substantially altered ecosystem functioning and community composition.
许多微生物光合自养生物依靠异养细菌来完成基本功能。然而，环境变化可能会改变或消除这种相互作用。我们研究了在三种聚球藻菌株（聚球藻菌株CC9311和WH8102以及原绿球藻菌株MIT9312）与“辅助”细菌麦克劳德氏交替单胞菌EZ55的共培养物中，改变pCO₂对基因转录的影响。与蓝细菌共培养导致EZ55中上调和下调基因的数量比单独的pCO₂处理多得多。通路分析显示，参与碳水化合物代谢、应激反应和趋化作用的基因转录存在显著差异，在与不同蓝细菌菌株共培养时上调或下调模式不同。EZ55中有机和无机营养转运蛋白及分解代谢基因的基因转录模式表明，在pCO₂升高（800 ppm）条件下，培养基中可用的资源发生了变化。总之，转录模式的变化与这样一种可能性一致，即在两种pCO₂条件下，蓝细菌排泄物的组成发生了变化，导致共培养物中两个成员都出现了广泛的生态生理变化。此外，在800 ppm pCO₂条件下，MIT9312/EZ55共培养物中氧化应激基因的显著下调与在此条件下预测的光呼吸副产物（即乙醇酸/2-磷酸甘油酸）可用性降低以及观察到的EZ55内部氧化应激负荷降低之间存在联系，这为之前观察到的在pCO₂升高条件下EZ55对MIT9312缺乏“帮助”提供了一种可能的解释。如果随着大气pCO₂增加，海洋中微生物生态生理发生类似的广泛变化，可能会导致生态系统功能和群落组成发生重大改变。
