Abstract

Several species of bacteria undergo continuous modifications of cellular fitness under nutrition or physical stress conditions. The variation of the cell dimensions is one of the characteristics which strongly depends on nutrition. Cell shape and dimension during extended periods of starvation are usually followed in-vivo by optical microscopy. However, classical microscopy has not been able to discriminate cells which remain active or restores their activity after dimension shrinking from those cells which arc damaged to an extent that they could not recover on the route leading to cell death. By using near field optical microscopy (SNOM), we have investigated in-vivo the morphological, structural and ultra structural evolution of a Pseudomonas Auriginosa ATCC 27853 microbial population over a period of 45 days nutritional stress. SNOM provides simultaneously topography and optical images with subwavelength resolution. Our SNOM images show extant ultramicrobacteria (UMB) with dimensions in the range 245-478 nm as well as viable but not cultivable cells (VBNC), whose dimensions reach the micron scale.

© 2000 IEEE