TY - JOUR
T1 - Silica-induced protein (Sip) in thermophilic bacterium Thermus thermophilus responds to low iron availability
AU - Fujino, Yasuhiro
AU - Nagayoshi, Yuko
AU - Iwase, Makoto
AU - Yokoyama, Takushi
AU - Ohshima, Toshihisa
AU - Doi, Katsumi
N1 - Funding Information:
This work, including the efforts of Yasuhiro Fujino, was funded by Japan Society for the Promotion of Science (JSPS) (23780085). This work, including the efforts of Katsumi Doi, was funded by Japan Society for the Promotion of Science (JSPS) (26292182).
Publisher Copyright:
© 2016, American Society for Microbiology. All Rights Reserved.
PY - 2016/6/1
Y1 - 2016/6/1
N2 - Thermus thermophilus HB8 expresses silica-induced protein (Sip) when cultured in medium containing supersaturated silicic acids. Using genomic information, Sip was identified as a Fe3+-binding ABC transporter. Detection of a 1-kb hybridized band in Northern analysis revealed that sip transcription is monocistronic and that sip has its own terminator and promoter. The sequence of the sip promoter showed homology with that of the σA-dependent promoter, which is known as a housekeeping promoter in HB8. Considering that sip is transcribed when supersaturated silicic acids are added, the existence of a repressor is presumed. DNA microarray analysis suggested that supersaturated silicic acids and iron deficiency affect Thermus cells similarly, and enhanced sip transcription was detected under both conditions. This suggested that sip transcription was initiated by iron deficiency and that the ferric uptake regulator (Fur) controlled the transcription. Three Fur gene homologues (TTHA0255, TTHA0344, and TTHA1292) have been annotated in the HB8 genome, and electrophoretic mobility shift assays revealed that the TTHA0344 product interacts with the sip promoter region. In medium containing supersaturated silicic acids, free Fe3+ levels were decreased due to Fe3+ immobilization on colloidal silica. This suggests that, because Fe3+ ions are captured by colloidal silica in geothermal water, Thermus cells are continuously exposed to the risk of iron deficiency. Considering that Sip is involved in iron acquisition, Sip production may be a strategy to survive under conditions of low iron availability in geothermal water.
AB - Thermus thermophilus HB8 expresses silica-induced protein (Sip) when cultured in medium containing supersaturated silicic acids. Using genomic information, Sip was identified as a Fe3+-binding ABC transporter. Detection of a 1-kb hybridized band in Northern analysis revealed that sip transcription is monocistronic and that sip has its own terminator and promoter. The sequence of the sip promoter showed homology with that of the σA-dependent promoter, which is known as a housekeeping promoter in HB8. Considering that sip is transcribed when supersaturated silicic acids are added, the existence of a repressor is presumed. DNA microarray analysis suggested that supersaturated silicic acids and iron deficiency affect Thermus cells similarly, and enhanced sip transcription was detected under both conditions. This suggested that sip transcription was initiated by iron deficiency and that the ferric uptake regulator (Fur) controlled the transcription. Three Fur gene homologues (TTHA0255, TTHA0344, and TTHA1292) have been annotated in the HB8 genome, and electrophoretic mobility shift assays revealed that the TTHA0344 product interacts with the sip promoter region. In medium containing supersaturated silicic acids, free Fe3+ levels were decreased due to Fe3+ immobilization on colloidal silica. This suggests that, because Fe3+ ions are captured by colloidal silica in geothermal water, Thermus cells are continuously exposed to the risk of iron deficiency. Considering that Sip is involved in iron acquisition, Sip production may be a strategy to survive under conditions of low iron availability in geothermal water.
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U2 - 10.1128/AEM.04027-15
DO - 10.1128/AEM.04027-15
M3 - Article
C2 - 26994077
AN - SCOPUS:84971294696
SN - 0099-2240
VL - 82
SP - 3198
EP - 3207
JO - Applied and Environmental Microbiology
JF - Applied and Environmental Microbiology
IS - 11
ER -