Department of Microbiology, Agricultural University of Norway, P.O. Box 40, N-1432 Aas-NLH, Norway.
Appl Environ Microbiol. 1983 Apr;45(4):1188-95. doi: 10.1128/aem.45.4.1188-1195.1983.
Several isolates of bacteria and fungi from soil, together with cells released directly from soil, were studied with respect to buoyant density and dry weight. The specific volume (cubic centimeters per gram) of wet cells as measured in density gradients of colloidal silica was correlated with the percent dry weight of the cells and found to be in general agreement with calculations based on the partial specific volume of major cell components. The buoyant density of pure bacterial cultures ranged from 1.035 to 1.093 g/cm, and their dry-matter content ranged from 12 to 33% (wt/wt). Average values proposed for the conversion of bacterial biovolume into biomass dry weight are 1.09 g/cm and 30% dry matter. Fungal hyphae had buoyant densities ranging from 1.08 to 1.11 g/cm, and their dry-matter content ranged from 18 to 25% (wt/wt). Average values proposed for the conversion of hyphal biovolume into biomass dry weight are 1.09 g/cm and 21% dry matter. Three of the bacterial isolates were found to have cell capsules. The calculated buoyant density and percent dry weight of these capsules varied from 1.029 g/cm and 7% dry weight to 1.084 g/cm and 44% dry weight. The majority of the fungi were found to produce large amounts of extracellular material when grown in liquid cultures. This material was not produced when the fungi were grown on either sterile spruce needles or membrane filters on an agar surface. Fungal hyphae in litter were shown to be free from extracellular materials.
从土壤中分离出的几种细菌和真菌的菌株，以及直接从土壤中释放的细胞，都进行了浮力密度和干重的研究。用胶体硅密度梯度法测量的湿细胞的比容（立方厘米/克）与细胞的干重百分比相关，并与基于主要细胞成分的比容部分的计算结果基本一致。纯细菌培养物的浮力密度范围为 1.035 至 1.093 g/cm，其干物质含量范围为 12%至 33%（wt/wt）。将细菌生物量转化为生物量干重的平均建议值为 1.09 g/cm 和 30%干物质。真菌菌丝的浮力密度范围为 1.08 至 1.11 g/cm，其干物质含量范围为 18%至 25%（wt/wt）。将菌丝体生物量转化为生物量干重的平均建议值为 1.09 g/cm 和 21%干物质。发现其中 3 种细菌分离物具有细胞荚膜。这些荚膜的计算浮力密度和干重百分比从 1.029 g/cm 和 7%干重到 1.084 g/cm 和 44%干重不等。当在液体培养基中生长时，大多数真菌产生大量的细胞外物质。当真菌在无菌云杉针或琼脂表面上的膜过滤器上生长时，不会产生这种物质。从凋落物中的真菌菌丝中可以看出，它们没有细胞外物质。
