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Abstract

Cell envelope formation depends on the balance between growth in cell volume (RNA-
synthesis), and in cell number (DNA-synthesis). This balance is ruled by rate and phase of
growth. Thus, steady and transient states in bacterioplankton can be described by shape or age
distributions, and mean cell volumes of age groups. The age-independent frequency distributions
of cell width represent activity spectra, or population heterogenity. The method is based on
half-automatic length-width measurements on scanning electron micrographs. In diurnal studies,
it shows alternating peaks for build-up of cell material and division, a¡rd mechanisms for bacterial
successions, resp. starvation/survival strategies. Seasonal patterns are partly paradoxical (e.g.,
low mean cell volumes at high activities), presumably due to yet unclear community effects like
grazing.