Department of Chemistry, St. John's University New York, NY, USA.
Department of Chemistry and Geochemistry, Colorado School of Mines Golden, CO, USA.
Front Chem. 2016 Mar 30;4:5. doi: 10.3389/fchem.2016.00005. eCollection 2016.
Biological production and decay of the reactive oxygen species (ROS) hydrogen peroxide (H2O2) and superoxide (O[Formula: see text]) likely have significant effects on the cycling of trace metals and carbon in marine systems. In this study, extracellular production rates of H2O2 and O[Formula: see text] were determined for five species of marine diatoms in the presence and absence of light. Production of both ROS was measured in parallel by suspending cells on filters and measuring the ROS downstream using chemiluminescence probes. In addition, the ability of these organisms to break down O[Formula: see text] and H2O2 was examined by measuring recovery of O[Formula: see text] and H2O2 added to the influent medium. O[Formula: see text] production rates ranged from undetectable to 7.3 × 10(-16) mol cell(-1) h(-1), while H2O2 production rates ranged from undetectable to 3.4 × 10(-16) mol cell(-1) h(-1). Results suggest that extracellular ROS production occurs through a variety of pathways even amongst organisms of the same genus. Thalassiosira spp. produced more O[Formula: see text] in light than dark, even when the organisms were killed, indicating that O[Formula: see text] is produced via a passive photochemical process on the cell surface. The ratio of H2O2 to O[Formula: see text] production rates was consistent with production of H2O2 solely through dismutation of O[Formula: see text] for T. oceanica, while T. pseudonana made much more H2O2 than O[Formula: see text]. T. weissflogii only produced H2O2 when stressed or killed. P. tricornutum cells did not make cell-associated ROS, but did secrete H2O2-producing substances into the growth medium. In all organisms, recovery rates for killed cultures (94-100% H2O2; 10-80% O[Formula: see text]) were consistently higher than those for live cultures (65-95% H2O2; 10-50% O[Formula: see text]). While recovery rates for killed cultures in H2O2 indicate that nearly all H2O2 was degraded by active cell processes, O[Formula: see text] decay appeared to occur via a combination of active and passive processes. Overall, this study shows that the rates and pathways for ROS production and decay vary greatly among diatom species, even between those that are closely related, and as a function of light conditions.
活性氧（ROS）物种如过氧化氢（H2O2）和超氧自由基（O[Formula: see text]）的生物产生和衰减可能对海洋系统中痕量金属和碳的循环有重大影响。在这项研究中，五种海洋硅藻在有光和无光的情况下，通过在滤器上悬浮细胞并使用化学发光探针测量下游的 ROS 来测定 H2O2 和 O[Formula: see text]的细胞外产生速率。此外，通过测量添加到流入培养基中的 O[Formula: see text]和 H2O2 的恢复情况，检查了这些生物体分解 O[Formula: see text]和 H2O2 的能力。O[Formula: see text]产生速率从不可检测到 7.3×10(-16) mol 细胞(-1) h(-1)，而 H2O2 产生速率从不可检测到 3.4×10(-16) mol 细胞(-1) h(-1)。结果表明，即使在同一属的生物中，细胞外 ROS 的产生也通过多种途径发生。塔玛斯氏藻属（Thalassiosira spp.）在光照下产生的 O[Formula: see text]比黑暗中多，即使生物被杀死也是如此，这表明 O[Formula: see text]是通过细胞表面的被动光化学过程产生的。H2O2 与 O[Formula: see text]产生速率的比值与 H2O2 仅通过 O[Formula: see text]歧化产生一致，而塔玛斯氏藻属（T. pseudonana）产生的 H2O2 比 O[Formula: see text]多得多。塔玛斯氏藻属（T. weissflogii）只有在受到胁迫或杀死时才会产生细胞相关的 ROS。菱形藻属（P. tricornutum）细胞不产生细胞相关的 ROS，但会将产生 H2O2 的物质分泌到生长培养基中。在所有生物中，死亡培养物（H2O2 为 94-100%；O[Formula: see text]为 10-80%）的回收率始终高于活培养物（H2O2 为 65-95%；O[Formula: see text]为 10-50%）。虽然死亡培养物的 H2O2 回收率表明几乎所有的 H2O2 都被主动细胞过程降解，但 O[Formula: see text]的衰减似乎通过主动和被动过程的组合发生。总的来说，这项研究表明，ROS 产生和衰减的速率和途径在硅藻物种之间差异很大，即使是在密切相关的物种之间，也因光照条件而异。
