Full text loading...
Chapter 16 : Morphological and Physiological Evidence for a Developmental Cycle in Legionella pneumophila
This chapter focuses on the cyclical nature of some morphological and physiological changes that take place in infected HeLa cells and during growth in vitro. Coverslip cultures of HeLa cells were infected with purified mature intracellular forms (MIFs), and changes in Gimenez staining were followed for up to 3 days. The bacterial strains used throughout these studies were Lp1-SVir and 2064, two virulent strains previously reported and characterized. Cultures with 100% green forms (after Gimenez staining) were identified upon growth of Legionella pneumophila on buffered charcoal-yeast extract (BCYE) plates. Rowbotham reported earlier that infection of amoebae resulted in the formation of small, highly motile, and infectious legionellae that are believed to be equivalent to the HeLa-derived MIFs reported. Purified MIFs were placed in buffered yeast extract (BYE) and their growth was followed through viable cell counts. Researchers concluded that the green forms arising in the BYE cultures were replicating bacteria that developed from the MIFs originally used as inoculum. In summary, L. pneumophila undergoes cyclical morphological and physiological changes that suggest the existence of a developmental program.