Limits...
Significance of four methionine sulfoxide reductases in Staphylococcus aureus.

Singh VK, Vaish M, Johansson TR, Baum KR, Ring RP, Singh S, Shukla SK, Moskovitz J - PLoS ONE (2015)

Bottom Line: Cell wall-active antibiotics cause elevated synthesis of methionine sulfoxide reductases (Msrs: MsrA1 and MsrB) in S. aureus.MsrA and MsrB enzymes reduce S-epimers and R-epimers of methionine sulfoxide, respectively, that are generated under oxidative stress.Overall, the data suggests that MsrA1 may be an important virulence factor and MsrB probably plays a balancing act to counter the effect of MsrA1 in S. aureus.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbiology and Immunology, A.T. Still University of Health Sciences, Kirksville, Missouri, United States of America.

ABSTRACT
Staphylococcus aureus is a major human pathogen and emergence of antibiotic resistance in clinical staphylococcal isolates raises concerns about our ability to control these infections. Cell wall-active antibiotics cause elevated synthesis of methionine sulfoxide reductases (Msrs: MsrA1 and MsrB) in S. aureus. MsrA and MsrB enzymes reduce S-epimers and R-epimers of methionine sulfoxide, respectively, that are generated under oxidative stress. In the S. aureus chromosome, there are three msrA genes (msrA1, msrA2 and msrA3) and one msrB gene. To understand the precise physiological roles of Msr proteins in S. aureus, mutations in msrA1, msrA2 and msrA3 and msrB genes were created by site-directed mutagenesis. These mutants were combined to create a triple msrA (msrA1, msrA2 and msrA3) and a quadruple msrAB (msrA1, msrA2, msrA3, msrB) mutant. These mutants were used to determine the roles of Msr proteins in staphylococcal growth, antibiotic resistance, adherence to human lung epithelial cells, pigment production, and survival in mice relative to the wild-type strains. MsrA1-deficient strains were sensitive to oxidative stress conditions, less pigmented and less adherent to human lung epithelial cells, and showed reduced survival in mouse tissues. In contrast, MsrB-deficient strains were resistant to oxidants and were highly pigmented. Lack of MsrA2 and MsrA3 caused no apparent growth defect in S. aureus. In complementation experiments with the triple and quadruple mutants, it was MsrA1 and not MsrB that was determined to be critical for adherence and phagocytic resistance of S. aureus. Overall, the data suggests that MsrA1 may be an important virulence factor and MsrB probably plays a balancing act to counter the effect of MsrA1 in S. aureus.

No MeSH data available.


Related in: MedlinePlus

Growth curve of the wild-type S. aureus strain and its derivative msr mutants in TSB.Values indicate the average of two independent experiments.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4334518&req=5

pone.0117594.g002: Growth curve of the wild-type S. aureus strain and its derivative msr mutants in TSB.Values indicate the average of two independent experiments.

Mentions: In growth kinetic experiments, the mutants specifically lacking MsrA1 or all three MsrA proteins showed slightly slower growth rate in TSB at 37°C (Fig. 2). Deletion of msrA2, msrA3, msrB, or msrA1-msrB had no apparent effect on the growth of the mutant cell compared to the growth of the wild-type S. aureus SH1000 (Fig. 2). When the Msr deficient mutants were cultured in TSB supplemented with 4.4 mM H2O2, the S. aureus strains lacking MsrA1 failed to grow (Fig. 3A). In the case of the combinatorial mutants, no growth was recorded for the triple msrA mutant even after 16 h in TSB with 8.8 mM H2O2 (Fig. 3B). The amount of H2O2 was raised to 8.8 mM in growth studies utilizing the combinatorial mutants to assess the resistance of MsrB-deficient S. aureus relative to other strains (Fig. 3B). The S. aureus strains that lacked MsrB (msrB, msrA1-msrB and the quadruple msrAB mutants) were moderately resistant to the presence of H2O2 in these growth experiments (Fig. 3B). The MsrB-deficient strains of methicillin-resistant S. aureus BB270 demonstrated better growth even in the presence of a cell wall-active antibiotic, oxacillin (Fig. 3C). In the MIC studies, the S. aureus strains deficient in MsrB were more resistant to H2O2 (Table 4). A similar increase in resistance to oxacillin and other cell wall-active antibiotics was observed in the case of MsrB-deficient S. aureus (Table 5). The strains that lacked MsrA1 were susceptible to oxidative stress conditions and the S. aureus strain that lacked all three MsrA proteins (the triple msrA mutant) showed most sensitivity to oxidants (Table 4). No such increase in sensitivity was noted in MsrA-deficient S. aureus to cell-wall active antibiotics (Table 5).


Significance of four methionine sulfoxide reductases in Staphylococcus aureus.

Singh VK, Vaish M, Johansson TR, Baum KR, Ring RP, Singh S, Shukla SK, Moskovitz J - PLoS ONE (2015)

Growth curve of the wild-type S. aureus strain and its derivative msr mutants in TSB.Values indicate the average of two independent experiments.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4334518&req=5

pone.0117594.g002: Growth curve of the wild-type S. aureus strain and its derivative msr mutants in TSB.Values indicate the average of two independent experiments.
Mentions: In growth kinetic experiments, the mutants specifically lacking MsrA1 or all three MsrA proteins showed slightly slower growth rate in TSB at 37°C (Fig. 2). Deletion of msrA2, msrA3, msrB, or msrA1-msrB had no apparent effect on the growth of the mutant cell compared to the growth of the wild-type S. aureus SH1000 (Fig. 2). When the Msr deficient mutants were cultured in TSB supplemented with 4.4 mM H2O2, the S. aureus strains lacking MsrA1 failed to grow (Fig. 3A). In the case of the combinatorial mutants, no growth was recorded for the triple msrA mutant even after 16 h in TSB with 8.8 mM H2O2 (Fig. 3B). The amount of H2O2 was raised to 8.8 mM in growth studies utilizing the combinatorial mutants to assess the resistance of MsrB-deficient S. aureus relative to other strains (Fig. 3B). The S. aureus strains that lacked MsrB (msrB, msrA1-msrB and the quadruple msrAB mutants) were moderately resistant to the presence of H2O2 in these growth experiments (Fig. 3B). The MsrB-deficient strains of methicillin-resistant S. aureus BB270 demonstrated better growth even in the presence of a cell wall-active antibiotic, oxacillin (Fig. 3C). In the MIC studies, the S. aureus strains deficient in MsrB were more resistant to H2O2 (Table 4). A similar increase in resistance to oxacillin and other cell wall-active antibiotics was observed in the case of MsrB-deficient S. aureus (Table 5). The strains that lacked MsrA1 were susceptible to oxidative stress conditions and the S. aureus strain that lacked all three MsrA proteins (the triple msrA mutant) showed most sensitivity to oxidants (Table 4). No such increase in sensitivity was noted in MsrA-deficient S. aureus to cell-wall active antibiotics (Table 5).

Bottom Line: Cell wall-active antibiotics cause elevated synthesis of methionine sulfoxide reductases (Msrs: MsrA1 and MsrB) in S. aureus.MsrA and MsrB enzymes reduce S-epimers and R-epimers of methionine sulfoxide, respectively, that are generated under oxidative stress.Overall, the data suggests that MsrA1 may be an important virulence factor and MsrB probably plays a balancing act to counter the effect of MsrA1 in S. aureus.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbiology and Immunology, A.T. Still University of Health Sciences, Kirksville, Missouri, United States of America.

ABSTRACT
Staphylococcus aureus is a major human pathogen and emergence of antibiotic resistance in clinical staphylococcal isolates raises concerns about our ability to control these infections. Cell wall-active antibiotics cause elevated synthesis of methionine sulfoxide reductases (Msrs: MsrA1 and MsrB) in S. aureus. MsrA and MsrB enzymes reduce S-epimers and R-epimers of methionine sulfoxide, respectively, that are generated under oxidative stress. In the S. aureus chromosome, there are three msrA genes (msrA1, msrA2 and msrA3) and one msrB gene. To understand the precise physiological roles of Msr proteins in S. aureus, mutations in msrA1, msrA2 and msrA3 and msrB genes were created by site-directed mutagenesis. These mutants were combined to create a triple msrA (msrA1, msrA2 and msrA3) and a quadruple msrAB (msrA1, msrA2, msrA3, msrB) mutant. These mutants were used to determine the roles of Msr proteins in staphylococcal growth, antibiotic resistance, adherence to human lung epithelial cells, pigment production, and survival in mice relative to the wild-type strains. MsrA1-deficient strains were sensitive to oxidative stress conditions, less pigmented and less adherent to human lung epithelial cells, and showed reduced survival in mouse tissues. In contrast, MsrB-deficient strains were resistant to oxidants and were highly pigmented. Lack of MsrA2 and MsrA3 caused no apparent growth defect in S. aureus. In complementation experiments with the triple and quadruple mutants, it was MsrA1 and not MsrB that was determined to be critical for adherence and phagocytic resistance of S. aureus. Overall, the data suggests that MsrA1 may be an important virulence factor and MsrB probably plays a balancing act to counter the effect of MsrA1 in S. aureus.

No MeSH data available.


Related in: MedlinePlus