Fig. 4.

Changes of pneumococcal gene expression in the presence of NTHi. Relative mRNA levels of pneumococcal lytA, lytB, lytC, cbpD and ply were measured by qPCR, normalized to a housekeeping gene (shikimate 5-dehydrogenase). The data represented the folds of relative mRNA levels of genes in the co-culture group to those in TIGR4 alone group. (a). Pneumococcal genes involved in autolysis and fratricide were significantly down-regulated in the presence of NTHi. The expression levels of lytA, lytB, lytC genes were not significantly different in 16 hour cultures of TIGR4 alone and mixed culture with 86028NP but cbpD was down-regulated significantly in the mixed culture compared to TIGR4 alone. Both lytA and cbpD gene expressions were significantly down-regulated at the 24 hour time point in the mixed culture compared to TIGR4 alone culture. Another gene, lytB, which isn’t involved in fratricide, didn’t change significantly either between different cultures or different time points. The bacterial cultures and qPCR were performed four times independently. (b). Expression of pneumococcal ply gene was down-regulated in the presence of NTHi. *: P<0.05; **: P<0.01.