Biology subjects

Schuster, C. F.

Publications and source records attributed to Schuster, C. F..

3 recordsLinked to original sources

bioRxiv2023

Histidine and its uptake are essential for the growth of Staphylococcus aureus at low pH

Staphylococcus aureus is an opportunistic pathogen capable of causing many different human diseases. During colonization and infection, S. aureus will encounter a range of hostile environments, including acidic conditions such as those found on the skin and within macrophages. However, little is known about the mechanisms that S. aureus uses to detect and respond to low pH. Here, we employed a transposon sequencing approach to determine on a genome-wide level the genes required or detrimental for growth at low pH. We identified 31 genes that were essential for the growth of S. aureus at pH 4.5 and confirmed the importance of many of them through follow up experiments using mutant strains inactivated for individual genes. Most of the genes identified code for proteins with functions in cell wall assembly and maintenance. These data suggest that the cell wall has a more important role than previously appreciated in promoting bacterial survival when under acid stress. We also identified several novel processes previously not linked to the acid stress response in S. aureus. These include aerobic respiration and histidine transport, the latter by showing that one of the most important genes, SAUSA300_0846, codes for a previously uncharacterized histidine transporter. We show that an S. aureus SAUSA300_0846 mutant is unable to maintain its cytosolic pH, thereby revealing an important function for histidine and its transport in buffering the intracellular pH in bacteria. Author summaryStaphylococcus aureus is an important human bacterial pathogen that can cause a range of diseases. During infection, the pathogen will encounter a hostile environment within the human host, including acidic conditions such as those found on the skin and within macrophages. The bacterium has developed sophisticated strategies to survive and grow under such harsh conditions. Here we performed a genome wide screen to identify factors that are required by this pathogen to survive under acid stress conditions and identified several novel processes including histidine uptake. Understanding the response of S. aureus to deal with acid stress conditions will help us better manage infections.

microbiology↗

bioRxiv2019

High-throughput transposon sequencing highlights cell wall as an important barrier for osmotic stress in methicillin resistant Staphylococcus aureus and underlines a tailored response to different osmotic stressors

Staphylococcus aureus is an opportunistic pathogen that can cause soft tissue infections but is also a frequent cause of foodborne illnesses. One contributing factor for this food association is its high salt tolerance allowing this organism to survive commonly used food preservation methods. How this resistance is mediated is poorly understood, particularly during long-term exposure. In this study, we used TN-seq to understand how the responses to osmotic stressors differ. Our results revealed distinctly different long-term responses to NaCl, KCl and sucrose stresses. In addition, we identified the DUF2538 domain containing gene SAUSA300_0957 (gene 957) as essential under salt stress. Interestingly, a 957 mutant was less susceptible to oxacillin and showed increased peptidoglycan crosslinking. The salt sensitivity phenotype could be suppressed by amino acid substitutions in the transglycosylase domain of the penicillin binding protein Pbp2, and these changes restored the peptidoglycan crosslinking to WT levels. These results indicate that increased crosslinking of the peptidoglycan polymer can be detrimental and highlight a critical role of the bacterial cell wall for osmotic stress resistance. This study will serve as a starting point for future research on osmotic stress response and help develop better strategies to tackle foodborne staphylococcal infections.

microbiology↗

bioRxiv2017

Cyclic-di-adenosine monophosphate (c-di-AMP) is required for osmotic regulation in Staphylococcus aureus but dispensable for viability in anaerobic conditions

Cyclic di-adenosine monophosphate (c-di-AMP) is a recently discovered signaling molecule important for the survival of Firmicutes, a large bacterial group that includes notable pathogens such as Staphylococcus aureus. However, the exact role of this molecule has not been identified. dacA, the S. aureus gene encoding the diadenylate cyclase enzyme required for c-di-AMP production, cannot be deleted when bacterial cells are grown in rich medium, indicating that c-di-AMP is required for growth in this condition. Here, we report that an S. aureus dacA mutant can be generated in chemically defined medium. Consistent with previous findings, this mutant had a severe growth defect when cultured in rich medium. Using this growth defect in rich medium, we selected for suppressor strains with improved growth to identify c-di-AMP-requiring pathways. Mutations bypassing the essentiality of dacA were identified in alsT and opuD, encoding a predicted amino acid and osmolyte transporter, the latter of which we show here to be the main glycine betaine-uptake system in S. aureus. Inactivation of these transporters likely prevents the excessive osmolyte and amino acid accumulation in the cell, providing further evidence for a key role of c-di-AMP in osmotic regulation. Suppressor mutations were also obtained in hepS, hemB, ctaA and qoxB, coding for proteins required for respiration. Furthermore, we show that dacA is dispensable for growth in anaerobic conditions. Together, these finding reveal an essential role for the c-di-AMP signaling network in aerobic, but not anaerobic, respiration in S. aureus.

microbiology↗