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Chapter 53 : The Type II Protein Secretion System of Legionella pneumophila Is Important for Growth in Iron-Rich Media and Survival in Tap Water at Low Temperatures
The Type II Protein Secretion System of Legionella pneumophila Is Important for Growth in Iron-Rich Media and Survival in Tap Water at Low Temperatures, Page 1 of 2< Previous page Next page > /docserver/preview/fulltext/10.1128/9781555815660/9781555813901_Chap53-1.gif /docserver/preview/fulltext/10.1128/9781555815660/9781555813901_Chap53-2.gif
The type II protein secretion system of Legionella pneumophila is important for bacterial survival in protozoa, macrophages, and the lungs of A/J mice. Presently, L. pneumophila is known to express both type II and type IV secretion systems. Type II secretion (lsp) mutants of L. pneumophila grow normally in bacteriologic media at 30 to 37°C. The low-temperature defect of lsp mutants of L. pneumophila serogroup 1 strain 130b was partially due to the presence of 0.25 g/liter ferric pyrophosphate in the growth media, since bacterial growth on agar plates at 25°C improved significantly when that supplement was omitted. The inhibitory effect of iron was specific to the lsp mutant and to low-temperature growth, since the growth of wild type at 25°C did not change with variations in the amount of supplemental iron, and the growth of the lsp mutant was not negatively influenced by iron supplementation when incubated at 37°C. In the environment, L. pneumophila is found in freshwater and man-made water systems. In sum, the results presented indicate that the L. pneumophila type II secretion system is not only important for growth at 35 to 37°C in host cells but is also critical for extracellular growth and survival at lower temperatures, including iron-rich bacteriological media and environmental water samples. Thus, type II secretion appears to play a central and multifaceted role in the natural history of Legionnaires’ disease.