THE ELEMENTAL COMPOSITION OF BACTERIA - A SIGNATURE OF GROWTH-CONDITIONS

X-ray microanalysis combined with Transmission Electron Microscopy (TE M) has been employed to measure cell quotas of P:C, N:C and O:C of ind ividual cells from cultures and natural microbial communities. The rel evance of such data for evaluation of nutrient availability and growth is discussed according to the Droop model. Using minimum subsistent q uotas of 0.031 (P:C) and 0.17 (N:C) and mu(max) of 1 h(-1) we have bee n able to identify some of the criteria for nutrient limited growth, b ut energy/carbon limitation will interfere with interpretation of thes e data. An additional signature for growth limitation may be the O:C r atio for which preliminary data indicate values of > 0.40 for growing cells and < 0.25 for dormant or stationary phase cells. (C) 1997 Elsev ier Science Ltd.