Borrelia burgdorferi σ54 is required for mammalian infection and vector transmission but not for tick colonization

MA Fisher, D Grimm, AK Henion… - Proceedings of the …, 2005 - National Acad Sciences
MA Fisher, D Grimm, AK Henion, AF Elias, PE Stewart, PA Rosa, FC Gherardini
Proceedings of the National Academy of Sciences, 2005National Acad Sciences
Previous studies have shown that a σ54–σS cascade regulates the expression of a few key
lipoproteins in Borrelia burgdorferi, the agent of Lyme disease. Here, we demonstrate that
these sigma factors, both together and independently, regulate a much more extensive
number of genes and cellular processes. Microarray analyses of σ54 and σS mutant strains
identified 305 genes regulated by σ54 and 145 regulated by σS, whereas the σ54–σS
regulatory cascade appears to control 48 genes in B. burgdorferi. In silico analyses revealed …
Previous studies have shown that a σ54–σS cascade regulates the expression of a few key lipoproteins in Borrelia burgdorferi, the agent of Lyme disease. Here, we demonstrate that these sigma factors, both together and independently, regulate a much more extensive number of genes and cellular processes. Microarray analyses of σ54 and σS mutant strains identified 305 genes regulated by σ54 and 145 regulated by σS, whereas the σ54–σS regulatory cascade appears to control 48 genes in B. burgdorferi. In silico analyses revealed that nearly 80% of genes with altered expression in the σ54 mutant were linked to potential σ54-dependent promoters. Many σ54-regulated genes are expressed in vivo, and through genetic complementation of the mutant, we demonstrated that σ54 was required by B. burgdorferi to infect mammals. Surprisingly, σ54 mutants were able to infect Ixodes scapularis ticks and be maintained for at least 24 wk after infection, suggesting the σ54–σS regulatory network was not involved in long-term survival in ticks. However, σ54 mutants did not enter the salivary glands during tick feeding, indicating that σ54-regulated genes were involved in the transmission process.
National Acad Sciences