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Under a moderately-high magnification of 6500X, this colorized scanning electron micrograph (SEM) depicted a large number of Gram-negative Legionella pneumophila bacteria. Please see PHIL 11092 through 11152 for additional SEMs of these organisms, specifically PHIL 11111 for a black and white version of this image.

You’ll note that a number of these bacteria seem to display an elongated-rod morphology. L. pneumophila are known to most frequently exhibit this configuration when grown in broth, however, they can also elongate when plate-grown cells age, as it was in this case, especially when they’ve been refrigerated. The usual L. pneumophila morphology consists of stout, fat bacilli, which is the case for the vast majority of the organisms depicted here.
Created: 2009