Calfee Benjamin C, Bowden Emily C, Zinser Erik R
Department of Microbiology, University of Tennessee, Knoxville, Tennessee, USA.
Appl Environ Microbiol. 2025 May 21;91(5):e0112824. doi: 10.1128/aem.01128-24. Epub 2025 Apr 10.
The marine cyanobacterium numerically dominates the phytoplankton communities in all lower latitude, open ocean environments. Having lost the catalase gene, is highly susceptible to exogenous hydrogen peroxide (HO) produced at the ocean's surface. Protection by HO-scavenging heterotrophic "helper" bacteria has been demonstrated in laboratory cultures and implicated as an important mechanism of survival in the ocean. Importantly, some other phytoplankton can also scavenge HO, suggesting these competing microbes may inadvertently protect . In this study, we assessed the ability of co-occurring phytoplankton, the cyanobacterium and picoeukaryotes and , to protect from HO exposure when cocultured at ecologically relevant abundances. All three genera could significantly degrade HO and diminish mortality during HO exposures simulating photochemical production and rainfall events. We suggest that these phytoplankton groups contribute significantly to the HO microbial sink of the open ocean, thus complicating their relationships with and perhaps contributing to the evolutionary history of .IMPORTANCEThe marine cyanobacterium is the most abundant photosynthetic organism on the planet and is crucially involved in microbial community dynamics and biogeochemical cycling in most tropical and subtropical ocean waters. This success is due, in part, to the detoxification of the reactive oxygen species hydrogen peroxide (HO) performed by "helper" organisms. Earlier work identified heterotrophic bacteria as helpers, and here, we demonstrate that rival cyanobacteria and picoeukaryotic phytoplankton can also contribute to the survival of during exposure to HO. Whereas heterotrophic bacteria helper organisms can benefit directly from promoting the survival of carbon-fixing cells, phytoplankton helpers may suffer a twofold injury: production of HO degrading enzymes constrains already limited resources in oligotrophic environments, and the activity of these enzymes bolsters the abundance of their numerically dominant competitor. These findings build toward a better understanding of the intricate dynamics and interactions that shape microbial community structure in the open ocean.
这种海洋蓝细菌在所有低纬度开阔海洋环境的浮游植物群落中在数量上占主导地位。由于失去了过氧化氢酶基因，它对海洋表面产生的外源过氧化氢（H₂O₂）高度敏感。在实验室培养中已证明由清除H₂O₂的异养“辅助”细菌提供的保护作用，并认为这是其在海洋中生存的重要机制。重要的是，其他一些浮游植物也可以清除H₂O₂，这表明这些竞争性微生物可能无意中保护了它。在本研究中，我们评估了共生浮游植物，即蓝细菌以及微微型真核生物和，在以生态相关丰度共培养时保护免受H₂O₂暴露的能力。在模拟光化学产生和降雨事件的H₂O₂暴露期间，所有这三个属都能显著降解H₂O₂并降低的死亡率。我们认为这些浮游植物群对开阔海洋的H₂O₂微生物汇有重大贡献，从而使其与的关系变得复杂，也许还促成了的进化史。重要性这种海洋蓝细菌是地球上最丰富的光合生物，在大多数热带和亚热带海洋水域的微生物群落动态和生物地球化学循环中起着至关重要的作用。这种成功部分归功于“辅助”生物对活性氧过氧化氢（H₂O₂）的解毒作用。早期的研究确定异养细菌为辅助者，而在这里，我们证明竞争的蓝细菌和微微型真核浮游植物在暴露于H₂O₂期间也有助于的生存。而异养细菌辅助生物可以通过促进固碳细胞的生存直接受益，浮游植物辅助者可能会受到双重损害：H₂O₂降解酶的产生限制了贫营养环境中本就有限的资源，并且这些酶的活性增加了其数量上占主导地位的竞争者的丰度。这些发现有助于更好地理解塑造开阔海洋微生物群落结构的复杂动态和相互作用。
