Determination, by spodography, of the intracellular distribution of mineral matter throughout the life history of Bacillus cereus.

Abstract

Knaysi, Georges (Cornell University, Ithaca, N. Y.). Determination, by spodography, of the intracellular distribution of mineral matter throughout the life history of Bacillus cereus. J. Bacteriol. 82:556-563. 1961.-The intracellular distribution of mineral matter throughout the life history of Bacillus cereus strain C(3) was investigated by microincineration for which the term spodography is suggested. The organism was grown in microcultures on collodion membranes supported by agar media. At various stages of development, microcultures were floated on distilled water, picked onto cover glasses, air-dried, and incinerated at 500 to 525 C. The mineral residue is deposited in situ and shows the distribution of mineral matter in the cells. Study of the spodograms thus obtained shows that in the spore mineral matter is concentrated in a peripheral layer surrounding a minerally poor core. As soon as the spore begins to germinate, often before one notes any change in its optical properties, the minerally rich layer increases in thickness while the core becomes gradually smaller and finally disappears. The germ cell appears nearly homogeneous, with evidence of mineral aggregation into discrete granules more readily seen in subsequent generations. The nuclei of the vegetative cells are sites of mineral accumulation. In the compound nuclei, minerals seem to be concentrated in a superficial ring around a minerally poor center. In the young forespore, mineral matter is homogeneously distributed. As the spore stage is approached, however, the mineral matter tends to occupy a peripheral position as in the completed spore. The results indicate that the calcium dipicolinate of the spore is principally in the minerally rich, peripheral layer. The relation of this layer to the other peripheral structures of the spore has not been determined. Observation was made with a phase microscope in dark contrast and using a dry objective.