Magnified 5000X, this digitally colorized scanning electron microscopic (SEM) image depicted a large grouping of Legionella pneumophila bacteria. Note the presence of an elongated-rod morphology in some organisms, seen in other images from this series as well. L. pneumophila frequently elongate when grown in broth, when plate-grown cells age, or when refrigerated, as in this case. Usually, L. pneumophila are stout, fat bacilli, which was the morphology displayed by the majority of these organisms. These bacteria originated on a 1 week-old culture plate (+/- 1 day), forming a single colony, at 37oC, on a buffered charcoal yeast extract (BCYE) medium with no antibiotics. The original sample was acid-treated for 15 min, to minimize fungal impurities, which would have inhibited the visualization of these organisms.