Ultrastructural aspects of the cell envelope of Legionella
The causal agents of Legionnaires’ Disease and related respiratory ailments in humans are gram-negative rod-shaped bacterial species belonging to the newly recognized genus, Legionella. During a comparative study of the ultrastructural organization of the cell boundary in several species, additional information regarding the presence and nature of various appendages of the cell envelope in these bacteria was observed.Cultures of L. pneumophils (including several serogroups) and L. micdadei were grown on charcoal yeast extract agar with increased humidity at 37°C. Samples were removed after 5 days of growth and immediately fixed in either glutaraldehyde/ruthenium red (GA/RR) followed by osmium tetroxide/ruthenium red (OSO4/RR) or glutaraldehyde/tannic acid (GA/TA) followed by osmium tetroxide. Thin sections were stained with uranyl acetate and lead citrate.