Characterization of the Staphylococcus aureus Heat Shock, Cold Shock, Stringent, and SOS Responses and Their Effects on Log-Phase mRNA Turnover

Abstract

Despite its being a leading cause of nosocomal and community-acquired infections, surprisingly little is known about Staphylococcus aureus stress responses. In the current study, Affymetrix S. aureus GeneChips were used to define transcriptome changes in response to cold shock, heat shock, stringent, and SOS responseinducing conditions. Additionally, the RNA turnover properties of each response were measured. Each stress response induced distinct biological processes, subsets of virulence factors, and antibiotic determinants. The results were validated by real-time PCR and stress-mediated changes in antimicrobial agent susceptibility. Collectively, many S. aureus stress-responsive functions are conserved across bacteria, whereas others are unique to the organism. Sets of small stable RNA molecules with no open reading frames were also components of each response. Induction of the stringent, cold shock, and heat shock responses dramatically stabilized most mRNA species. Correlations between mRNA turnover properties and transcript titers suggest that S. aureus stress response-dependent alterations in transcript abundances can, in part, be attributed to alterations in RNA stability. This phenomenon was not observed within SOS-responsive cells.

Role for dnaK locus in tolerance of multiple stresses in Staphylococcus aureus

“…An increased production of dnaK locus transcripts in response to heat shock is consistent with an earlier report (Ohta et al, 1994). However, these transcripts were not detected at an elevated level in a more recent global transcription profiling study aimed to characterize the staphylococcal heat shock, cold shock, stringent and SOS responses (Anderson et al, 2006). In the present study also, stress conditions such as oxidative stress had no effect on the expression of dnaK locus genes (Fig.…”

Implication of the NorB Efflux Pump in the Adaptation of Staphylococcus aureus to Growth at Acid pH and in Resistance to Moxifloxacin

“…These adaptations are multifaceted, involving changes in expression of many genes with various functions, but the specific mechanisms are not well studied. The acid stress response has been shown to include increased transcript levels of genes involved in utilization of urease (ureA, ureB, ureC, and ureF) and of nuoF, which encodes an NADH dehydrogenase, which can increase internal cell pH by assisting proton export from the bacterial cell (1,2,5,6,28). A decrease in transcripts encoding the F 0 F 1 ATPase was also observed, which was somewhat surprising since this F 0 F 1 ATPase is considered an important proton extrusion mechanism in several Gram-positive bacterial species, such as Streptococcus mutans (17).…”

“…S. aureus is also carried by healthy humans as part of the normal flora of the nose, throat, and skin. This pathogen can adapt to various unfavorable environmental conditions or stresses caused by variation in pH, temperature, or nutritive sources by activating several defense mechanisms, including the use of proton pumps to maintain the cellular pH at an acceptable level, or shifting the growth energy to adaptation mechanisms (1,2,28). These conditions may also serve as signals to the organism that are important for pathogenesis and fitness at specific sites of infection or colonization of the host.…”

Staphylococcus aureus promoter-lux reporters for drug discovery

“…As it is known that DNA-damaging agents activate recA, 18,27,28 S. aureus clone B was used to screen the 400 supernatants for these agents. Five percent of the strains activated light responses, and two, DCA3491 and DCA3492, were investigated further.…”