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Phospholipid turnover rates suggest that bacterial community growth rates in the open ocean are systematically underestimated
Limnology and Oceanography ( IF 4.5 ) Pub Date : 2020-03-27 , DOI: 10.1002/lno.11424
Kimberly J. Popendorf 1 , Michal Koblížek 2 , Benjamin A. S. Van Mooy 1
Affiliation  

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.

中文翻译:

磷脂周转率表明,公海中细菌群落的增长率被系统地低估了

表层海洋中的异养细菌在全球碳循环中起着至关重要的作用,这种作用的程度取决于它们的生长速度。尽管基于掺入放射性标记的胸苷和亮氨酸来确定细菌群落生长速率的方法已被广泛接受,但它们基于许多假设和简化。我们试图通过使用以前发表的方法在一系列开放海洋环境中比较细菌生长速率与细菌膜的周转速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。通过独立测量光异养细菌细菌叶绿素a中膜结合色素的周转率来支持这一点。 (0.85±0.09d -1)。相比之下,通过摄取放射性标记的胸苷和亮氨酸测得的细菌生长速率为0.12±0.08 d -1,完全在文献预期的范围内。我们探索了磷脂周转率与细菌生长速率之间的差异是否可以通过膜回收/重塑和其他因素来解释,但可以得出结论,放射性标记的胸苷和亮氨酸掺入方法大大低估了实际细菌的生长速率。我们使用一个简单的模型来表明,如果细菌比目前想象的要小,效率更高或这两个因素的结合,我们观察到的更快的细菌生长速度可以适应微生物碳预算的限制。
更新日期:2020-03-27
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