Guerrero R, Pedrós-Alió C, Schmidt T M, Mas J
Department of Microbiology, Autonomous University of Barcelona, Bellaterra, Spain.
Microbiologia. 1985 Sep;1(1-2):53-65.
Values of buoyant density of microorganisms reported in literature are widely divergent because of techniques used. Many of these involve centrifugation in density gradients formed by substances with high osmolarity which dehydrate the cells. In order to better understand the ranges of variation of density of microbial cells several approaches were taken. Firstly, samples from several natural aquatic habitats were taken and the densities of the microorganisms present determined. Secondly, experiments were performed with selected microorganisms to maximize density changes by forcing them to accumulate intracytoplasmic inclusions of dense materials or to loose their capsules. Finally, the relevant literature was reviewed. It could be demonstrated that most microorganisms have a density around 1.080 pg microns-3 when measured in low osmolarity media such as Percoll. However, many species are able to modify their density by as much as 7% (for instance, from 1.097 to 1.022 pg microns-3 in Thiocapsa roseopersicina, and similar variations in other bacteria), by incorporating substances into inclusions (sulfur, carbon, phosphorous storage materials, etc.), or by making capsules and/or gas vesicles. The relevance of buoyant density determinations for several aspects of microbial ecology and physiology is discussed.
由于所使用的技术，文献中报道的微生物浮力密度值差异很大。其中许多技术涉及在由高渗透压物质形成的密度梯度中进行离心，这些物质会使细胞脱水。为了更好地了解微生物细胞密度的变化范围，采取了几种方法。首先，从几个天然水生栖息地采集样本，并测定其中存在的微生物的密度。其次，对选定的微生物进行实验，通过迫使它们积累密集物质的胞质内含物或去除其荚膜来使密度变化最大化。最后，查阅了相关文献。可以证明，当在低渗透压介质（如Percoll）中测量时，大多数微生物的密度约为1.080 pg微米-3。然而，许多物种能够通过将物质纳入内含物（硫、碳、磷储存物质等），或通过形成荚膜和/或气泡，将其密度改变多达7%（例如，玫瑰色硫杆菌从1.097 pg微米-3变为1.022 pg微米-3，其他细菌也有类似变化）。本文讨论了浮力密度测定在微生物生态学和生理学几个方面的相关性。
