USE OF IMMUNOFLUORESCENCE TO VISUALIZE CELL-SPECIFIC GENE-EXPRESSION DURING SPORULATION IN BACILLUS-SUBTILIS

We have adapted immunofluorescence microscopy for use in Bacillus subtilis and have employed this procedure for visualizing cell-specific gene expression at early to intermediate stages of sporulation. Sporangia were doubly stained with propidium iodide to visualize the forespore and mother cell nucleoids and with fluorescein-conjugated antibodies to visualize the location of beta-galactosidase produced under the control of the sporulation RNA polymerase sigma factors sigma(E) and sigma(F). In confirmation and extension of earlier reports, we found that expression of a lacZ fusion under the control of sigma(E) was confined to the mother cell compartment of sporangia at the septation (II) and engulfment (III) stages of morphogenesis. Conversely, sigma(F)-directed gene expression was confined to the forespore compartment of sporangia at postseptation stages of development. Little indication was found for sigma(E)- or sigma(F)-directed gene expression prior to septation or in both compartments of postseptation sporangia. Gene expression under the control of the forespore sigma factor ac also exhibited a high level of compartmentalization. A high proportion of sporangia exhibited fluorescence in our immunostaining protocol, which should be suitable for the subcellular localization of sporulation proteins for which specific antibodies are available.