Mutational and transcriptional analyses of theStaphylococcus aureuslow-affinity proline transporter OpuD duringin vitrogrowth and infection of murine tissues

Abstract

Staphylococcus aureus continues to be a major health problem. This species' requirement for proline and proline transport from the extracellular environment is not well understood. Here, we identify a S. aureus low-affinity proline transport gene (opuD) with homology to the OpuD protein of Bacillus subtilis. Mutation of the opuD gene caused a significant decline in proline uptake under low affinity conditions as compared to wild-type, but the opuD mutant strain showed no significant attenuation in a murine abscess model of infection. The S. aureus opuD gene was transcriptionally activated during growth in moderate osmolarity media with high levels of proline or glycine betaine independent of SigB. In murine abscesses, the opuD gene was activated at a later time point, whereas opuD expression dropped over the course of an 18 h period within murine urinary tracts. Transcriptional regulation of opuD in S. aureus appears to be coordinated within this species when grown in moderate to high NaCl environments, but the level of extracellular proline had a marked effect on expression of this proline transport gene. The differential regulation of proline transport genes in S. aureus may be an adaptation for life in a variety of environments, including survival within the human body.

Comparative virulence studies and transcriptome analysis of Staphylococcus aureus strains isolated from animals

“…3 ) could be important for stress tolerance by increasing the fermentation products. Several other important genes for bacterial survival had a positive differential expression and those include trxA and cysK genes responsible for managing oxidative stress 45 , prop gene important for the bacterial survival in host body 46 , ImpB/MucB/SamB encoding genes responsible for protection against UV rays 47 , Ohr family gene crucial for organic hydroperoxide resistance 48 , and ureBCDEFG genes for urease activity essential in acid shock mechanism 49 . In contrast, many important stress related genes were down-regulated and among those were the ATP-dependent Clp protease B, molecular chaperones dnaJ and dnaK , heat-shock protein grpE , transcriptional regulator ctsR and heat-inducible transcription repressor hrcA .…”

Osmolyte transport inStaphylococcus aureusand the role in pathogenesis

“…Though these systems are similar, there are some major differences between the Gram-negative and Gram-positive low-affinity proline transport systems. One major difference is that the low‐affinity proline transport systems in S. aureus are optimally activated at NaCl concentrations ranging from 0.75 to 1.0 mol/L [ 17 , 35 ] , whereas the low-affinity proline transport systems in E. coli are inhibited by NaCl concentrations greater than 0.2 to 0.3 mol/L [ 29 , 36 ] . Other major differences include glycine betaine transport activity by the low-affinity proline transport system has not been conclusively established and there conflicting opinions and data presented for the glycine betaine transport activity for the low-affinity system [ 9 , 17 , 18 , 20 , 37 ] .…”

“…Sequencing of several S. aureus genomes has provided a wealth of information on the existence of several putative osmolyte transport systems in S. aureus [ 14 , 39 , 40 ] . All of the strains appear to have a conserved putP gene for high affinity transport of proline, although there appears to be homologs for both a proP gene [ 1 ] and opuD gene [ 21 , 35 ] ( Table 1 ). Additional analyses have shown that the opuD gene (encoding a low affinity proline transporter) is activated under osmotic stress conditions and OpuD transports proline under low affinity growth conditions [ 35 ] .…”

“…All of the strains appear to have a conserved putP gene for high affinity transport of proline, although there appears to be homologs for both a proP gene [ 1 ] and opuD gene [ 21 , 35 ] ( Table 1 ). Additional analyses have shown that the opuD gene (encoding a low affinity proline transporter) is activated under osmotic stress conditions and OpuD transports proline under low affinity growth conditions [ 35 ] . Furthermore, a mutation in the S. aureus proP gene also causes lower proline transport in media with high concentrations of proline (Schwan WR unpublished data).…”

Proteomic and Metabolomic Analyses of a Tea-Tree Oil-Selected Staphylococcus aureus Small Colony Variant

“…The relative concentration of RocD which is involved with ornithine and proline biosynthesis [57] was increased in SH1000-TTORS-1 (Table 1, Figure 2), and both ornithine and proline are increased in SH1000-TTORS-1 (Table 3, Figure 2). The increased proline accumulation could be attributed to the increased relative concentration of the proline/choline/glycine betaine transporter OpuD [58] in SH1000-TTORS-1 ( Table 1). Ornithine is synthesized from arginine during the urea cycle and is a precursor needed in the synthesis of glutamate and proline ( Figure 2) [57].…”