The typographical corrections below were made to the article on the date noted. These changes have been incorporated in the article and the details are documented here.

21 April 2004:

The word "Northern" was corrected to "northern" in four locations: in the methods section of the Abstract (...analyzed by western and Northern blot analyses...), in the first paragraph of the Methods section (For Northern blot analysis, cultures were...), in the second paragraph of the Results section (...was harvested and analyzed by Northern analysis...), and in Figure 2 (...analyzed by Northern analysis...).