Phospholipid turnover rates suggest that bacterial community growth rates in the open ocean are systematically underestimated
Phospholipid turnover rates suggest that bacterial community growth rates in the open ocean are systematically underestimated
复制标题
DOI：
10.1002/lno.11424
复制
发表时间：
2020-03
影响因子：
4.5
通讯作者：
Kimberly J. Popendorf;M. Koblížek;B. V. Van Mooy
中科院分区：
文献类型：
--
作者：
Kimberly J. Popendorf;M. Koblížek;B. V. Van Mooy
海洋表层的异养细菌在全球碳循环中起着关键作用，这种作用的大小取决于它们的生长速度。尽管基于放射性标记的胸苷和亮氨酸掺入的细菌群落生长速率测定方法被广泛接受，但它们基于许多假设和简化。我们试图通过在一系列开放海洋环境中使用先前公布的方法比较细菌生长率与细菌膜的周转率来独立评估这些方法。我们发现异养细菌磷脂的周转率平均为0.80 ± 0.35 d−1。这得到了光合异养细菌中膜结合色素的周转率（0.85 ± 0.09 d−1）的独立测量结果的支持。相比之下，通过摄取放射性标记的胸苷和亮氨酸测量的细菌生长速率为0.12 ± 0.08 d−1，完全在文献预期的范围内。我们探讨了磷脂周转率和细菌生长率之间的差异是否可以通过膜再循环/重塑和其他因素来解释，但得出的结论是，放射性标记的胸苷和亮氨酸掺入法大大低估了实际的细菌生长率。我们使用一个简单的模型来表明，如果细菌比目前认为的更小，生长效率更高，或者这两个因素的某种组合，那么我们观察到的更快的细菌生长速率可以在微生物碳预算的约束下进行调节。
Heterotrophic bacteria in the surface ocean play a critical role in the global carbon cycle and the magnitude of this role depends on their growth rates. Although methods for determining bacterial community growth rates based on incorporation of radiolabeled thymidine and leucine are widely accepted, they are based on a number of assumptions and simplifications. We sought to independently assess these methods by comparing bacterial growth rates to turnover rates of bacterial membranes using previously published methods in a range of open‐ocean settings. We found that turnover rates for heterotrophic bacterial phospholipids averaged 0.80 ± 0.35 d−1. This was supported by independent measurements of turnover rates of a membrane‐bound pigment in photoheterotrophic bacteria, bacteriochlorophyll a (0.85 ± 0.09 d−1). By contrast, bacterial growth rates measured by uptake of radiolabeled thymidine and leucine were 0.12 ± 0.08 d−1, well within the range expected from the literature. We explored whether the discrepancies between phospholipid turnover rates and bacterial growth rate could be explained by membrane recycling/remodeling and other factors, but were left to conclude that the radiolabeled thymidine and leucine incorporation methods substantially underestimated actual bacterial growth rates. We use a simple model to show that the faster bacterial growth rates we observed can be accommodated within the constraints of the microbial carbon budget if bacteria are smaller than currently thought, grow with greater efficiency, or some combination of these two factors.