Increased expression of Mg(2+) transport proteins enhances the survival of Salmonella enterica at high temperature.
Mg(2+) homeostasis is important for Salmonella pathogenesis. In Salmonella enterica, the transcription of the mgtA gene, which encodes a Mg(2+) transporter, is regulated by a Mg(2+)-sensing riboswitch [Cromie MJ, Shi Y, Latifi T, Groisman EA (2006) Cell 125:71-84]. In a genetic analysis of the determinants of thermotolerance in S. enterica serovar Typhimurium, we isolated the chr-1 mutation that increased the resistance of exponential phase cells to killing by high temperature. This mutation is a single base change in the mgtA riboswitch that causes high-level constitutive expression of mgtA. We showed that another mgtA riboswitch mutation, DeltaUTR(re-100), which had been constructed by Cromie et al., also confers similar increased thermotolerance. Surprisingly, the chr-1 mutation is located at a position that would not be predicted to be important for the regulatory function of the riboswitch. We obtained physiological evidence suggesting that the chr-1 mutation increases the cytosolic free Mg(2+) concentration. High-level expression of the heterologous MgtE Mg(2+) transport protein of Bacillus subtilis also enhanced the thermotolerance of S. enterica. We hypothesize that increased Mg(2+) accumulation might enhance thermotolerance by protecting the integrity of proteins or membranes, by mitigating oxidative damage or acting as an inducer of thermoprotective functions.
O'Connor
Kathleen
K
Department of Biological Sciences, Purdue University, West Lafayette, IN 47907, USA.
Fletcher
Susanne A
SA
Csonka
Laszlo N
LN
D000251:Adenosine Triphosphatases / Q000235:genetics*; D001426:Bacterial Proteins / Q000235:genetics*; D001483:Base Sequence; D027682:Cation Transport Proteins / Q000235:genetics*; D006358:Hot Temperature; D008274:Magnesium / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D012329:RNA, Bacterial / Q000737:chemistry / Q000235:genetics; D012335:RNA, Ribosomal / Q000737:chemistry / Q000235:genetics; D019779:Salmonella enterica / Q000166:cytology* / Q000502:physiology*; D012486:Salmonella typhimurium / Q000166:cytology / Q000502:physiology*
D001426:Bacterial Proteins; D027682:Cation Transport Proteins; D012329:RNA, Bacterial; D012335:RNA, Ribosomal; D000251:Adenosine Triphosphatases; C083836:MgtB protein, Salmonella typhimurium; D008274:Magnesium