Deletion of a Cation Transporter Promotes Lysis in Streptococcus pneumoniae

Abstract

Streptococcus pneumoniae is a significant human pathogen which causes respiratory and serious invasive diseases. Mg 2؉ is essential for life, and its concentration varies throughout the human body. Magnesium uptake plays an important role in the virulence of many bacterial pathogens. To study the Mg 2؉ uptake of S. pneumoniae strain D39, a mutant was generated in SPD1383, a P-type ATPase with homology to the Salmonella Mg 2؉ transporter MgtA, which has also been shown to be a Ca 2؉ exporter in strain TIGR4. Under low-Ca 2؉ conditions, mutation led to a growth defect in complex medium and the gene was nearly essential for growth under low-Mg 2؉ conditions. Addition of Mg 2؉ restored the normal growth of the mutant in all cases, but the addition of other divalent cations had no effect. Addition of Ca 2؉ , Mn 2؉ , and Zn 2؉ in the presence of high Mg 2؉ concentrations inhibited restoration of growth. The mutant was unable to proliferate in blood, which was also alleviated by the addition of Mg 2؉ . The protein was located in the membrane and produced in various S. pneumoniae strains and pathogenic streptococcal species. Surprisingly, mutation of the gene led to an elevated toxicity for endothelial cells. This was caused by an increased amount of pneumolysin in the medium, mediated by elevated lysis of the mutant. Thus, in this study, we uncovered a role for SPD1383 in Mg 2؉ uptake and hypothesize that the protein is a Mg 2؉/ Ca 2؉ antiporter. Furthermore, a disturbance in Mg 2؉ homeostasis seems to promote lysis of S. pneumoniae.

Pneumococcal Gene Complex Involved in Resistance to Extracellular Oxidative Stress

“…To control for accurate separation of the various fractions, cross-reacting antibodies against S. aureus TrxA (37) and antibodies against S. pneumoniae MgtA were used as controls for cytoplasmic and membrane proteins, respectively (Fig. 6B) (38). Thus, TlpA is a lipoprotein exclusively located in the pneumococcal membrane.…”

“…Fractionation of S. pneumoniae cells was performed essentially as described previously (38). S. pneumoniae was grown to the desired OD in BHI broth, after which the bacteria were spun down for 10 min at 7,000 rpm.…”

A Novel Initiation Mechanism of Death in Streptococcus pneumoniae Induced by the Human Milk Protein-Lipid Complex HAMLET and Activated during Physiological Death

“…The only annotations related to Ca 2ϩ transport in the two genomes were two P-type Ca 2ϩ -ATPase pumps (SP1551 and SP1623, TIGR4), the first of which has been char- acterized and shown to extrude Ca 2ϩ from the cell (43,44). However, HAMLET-induced depolarization and death were not dramatically changed in the presence of the P-type ATPase inhibitor sodium orthovanadate; if anything, death was slightly increased (p ϭ 0.04) (Fig.…”

Spermidine Biosynthesis and Transport Modulate Pneumococcal Autolysis

“…Furthermore, the activity of murein hydrolases is thought to be modulated by a complex process involving interactions with teichoic acids and is dependent on the ionic conditions within the cell wall microenvironment (reviewed in reference 26). The polyanionic matrix of the Gram-positive cell wall has a high capacity for binding cations, particularly Mg 2ϩ and Ca 2ϩ , and it has been shown that disturbing Mg 2ϩ homeostasis through deletion of the gene encoding its transport promotes lysis of S. pneumoniae (27). In view of this, the effect of Mg 2ϩ on the autolysis profiles of wild-type and mutant pneumococci was examined.…”