Abstract
In this study, we investigated the transcriptomic response of
Streptococcus pneumoniae
D39 to cysteine. Transcriptome comparison of the D39 wild-type grown at a restricted concentration of cysteine (0.03 mM) to one grown at a high concentration of cysteine (50 mM) in chemically-defined medium (CDM) revealed elevated expression of various genes/operons, i.e.,
spd-0150
,
metQ
,
spd-0431
,
metEF
,
gshT
,
spd-0618
,
fhs, tcyB
,
metB
-
csd
,
metA
,
spd-1898
,
yvdE
, and
cysK
, likely to be involved in the transport and utilization of cysteine and/or methionine. Microarray-based data were further confirmed by quantitative RT-PCR. Promoter
lacZ
-fusion studies and quantitative RT-PCR data showed that the transcriptional regulator CmbR acts as a transcriptional repressor of
spd-0150
,
metEF
,
gshT
,
spd-0618
,
tcyB
,
metA
, and
yvdE
, putatively involved in cysteine uptake and utilization. The operator site of CmbR in the promoter regions of CmbR-regulated genes is predicted and confirmed by mutating or deleting CmbR operator sites from the promoter regions of these genes.