FIG. 1.

Phase-contrast micrographs of bacteria visualized by microautoradiography following in situ hybridization of H. wrightii longitudinal root sections with ³³P-labeled rRNA probes. Magnification, ×1,000. Bacteria that retained probe appear black due to the deposition of silver grains from the photographic emulsion. (a) EUB probe for virtually all bacteria; (b) DSV probe for the sulfate-reducing Desulfovibrio species; (c) AW probe for the acetogens E. limosum and Acetobacterium. Cells hybridizing with the AW probe were found in dense clusters (arrow) on the outer root surface.