Su Qingxian, Bazylinski Dennis A, Jensen Marlene Mark
Department of Environmental and Resource Engineering, Technical University of Denmark, Lyngby, Denmark.
School of Life Sciences, University of Nevada at Las Vegas, Las Vegas, NV, United States.
Front Microbiol. 2023 Jun 15;14:1203805. doi: 10.3389/fmicb.2023.1203805. eCollection 2023.
Magnetotactic bacteria (MTB) are microorganisms widely inhabiting the oxic-anoxic interface of aquatic environments. Beside biomineralizing magnetic nanocrystals, MTBs are able to sequester various chemical elements (e.g., carbon and phosphorus) for the biogenesis of intracellular granules, like polyhydroxyalkanoate (PHA) and polyphosphate (polyP), making them potentially important in biogeochemical cycling. Yet, the environmental controls of intracellular storage of carbon and phosphorus in MTB remain poorly understood. Here, we investigated the influence of oxic, anoxic and transient oxic-anoxic conditions on intracellular storage of PHA and polyP in strain AMB-1. In the incubations with oxygen, transmission electron microscopy revealed intercellular granules highly rich in carbon and phosphorus, which were further interpreted as PHA and polyP based on chemical and Energy-Dispersive X-ray spectroscopy analysis. Oxygen had a strong effect on PHA and polyP storage in AMB-1 cells, as PHA and polyP granules accounted for up to 47 ± 23% and 5.1 ± 1.7% of the cytoplasmic space, respectively, during continuous oxic conditions, while granules disappeared in anoxic incubations. Poly 3-hydroxybutyrate (PHB) and poly 3-hydroxyvalerate (PHV) accounted for 0.59 ± 0.66% and 0.0033 ± 0.0088% of dry cell weight, respectively, in anoxic incubations, while the values increased by a factor of 7 and 37 after oxygen was introduced. The results highlight a tight link between oxygen, carbon and phosphorus metabolisms in MTB, where favorable oxic growth conditions can lead to metabolic induction of polyP and PHA granule biogenesis.
趋磁细菌（MTB）是广泛存在于水生环境有氧-缺氧界面的微生物。除了生物矿化磁性纳米晶体外，趋磁细菌还能够螯合各种化学元素（如碳和磷）用于细胞内颗粒（如聚羟基脂肪酸酯（PHA）和多聚磷酸盐（polyP））的生物合成，这使得它们在生物地球化学循环中具有潜在的重要性。然而，趋磁细菌细胞内碳和磷储存的环境控制仍知之甚少。在此，我们研究了有氧、无氧和短暂有氧-无氧条件对菌株AMB-1中PHA和polyP细胞内储存的影响。在有氧培养中，透射电子显微镜显示细胞间颗粒富含碳和磷，基于化学和能量色散X射线光谱分析，这些颗粒进一步被解释为PHA和polyP。氧气对AMB-1细胞中PHA和polyP的储存有强烈影响，在连续有氧条件下，PHA和polyP颗粒分别占细胞质空间的47±23%和5.1±1.7%，而在无氧培养中颗粒消失。在无氧培养中，聚3-羟基丁酸酯（PHB）和聚3-羟基戊酸酯（PHV）分别占干细胞重量的0.59±0.66%和0.0033±0.0088%，而引入氧气后，这些值分别增加了7倍和37倍。结果突出了趋磁细菌中氧、碳和磷代谢之间的紧密联系，其中有利的有氧生长条件可导致polyP和PHA颗粒生物合成的代谢诱导。
