In the Gram-positive pathogen Staphylococcus aureus, FtsH, a membrane-bound metalloprotease, plays a critical role in bacterial virulence and stress resistance. This protease is also known to sensitize methicillin-resistant Staphylococcus aureus (MRSA) to β-lactam antibiotics; however, the molecular mechanism is not known. Here, by the analysis of FtsH substrate mutants, we found that FtsH sensitizes MRSA specifically to β-lactams by degrading YpfP, the enzyme synthesizing the anchor molecule for lipoteichoic acid (LTA). Both the overexpression of FtsH and the disruption of ypfP-sensitized MRSA to β-lactams were observed. The knockout mutation in ftsH and ypfP increased the thickness of the cell wall. The β-lactam sensitization coincided with the production of aberrantly large LTA molecules. The combination of three mutations in the rpoC, vraB, and SAUSA300_2133 genes blocked the β-lactam-sensitizing effect of FtsH. Murine infection with the ypfP mutant could be treated by oxacillin, a β-lactam antibiotic ineffective against MRSA; however, the effective concentration of oxacillin differed depending on the S. aureus strain. Our study demonstrated that the β-lactam sensitizing effect of FtsH is due to its digestion of YpfP. It also suggests that the larger LTA molecules are responsible for the β-lactam sensitization phenotype, and YpfP is a viable target for developing novel anti-MRSA drugs.

Staphylococcus aureus is a versatile Gram-positive human pathogen infecting various human organs. The bacterium's versatility is partly due to efficient metabolic regulation via the carbon catabolite repression system (CCR). S. aureus is known to interconvert proline and arginine, and CCR represses the synthesis of both amino acids.

Background Curiosity on toxin–antitoxin modules has increased intensely over recent years as it is ubiquitously present in many bacterial genomes, including pathogens like Methicillin-resistant Staphylococcus aureus (MRSA). Several cellular functions of TA systems have been proposed however, their exact role in cellular physiology remains unresolved. Methods This study aims to find out the impact of the mazEF toxin–antitoxin module on biofilm formation, pathogenesis, and antibiotic resistance in an isolated clinical ST239 MRSA strain, by constructing mazE and mazF mutants using CRISPR–cas9 base-editing plasmid (pnCasSA-BEC). Transcriptome analysis (RNA-seq) was performed for the mazE antitoxin mutant in order to identify the differentially regulated genes. The biofilm formation was also assessed for the mutant strains. Antibiogram profiling was carried out for both the generated mutants followed by murine experiment to determine the pathogenicity of the constructed strains. Results For the first time our work showed, that MazF promotes cidA mediated cell death and lysis for biofilm formation without playing any significant role in host virulence as suggested by the murine experiment. Interestingly, the susceptibility to oxacillin, daptomycin and vancomycin was reduced significantly by the activated MazF toxin in the mazE mutant strain. Conclusions Our study reveals that activated MazF toxin leads to resistance to antibiotics like oxacillin, daptomycin and vancomycin. Therefore, in the future, any potential antibacterial drug can be designed to target MazF toxin against the problematic multi-drug resistant bug.

Symbiotic bacteria have to overcome stressful conditions present in association with the host. In the Burkholderia -bean bug symbiosis, we speculated that a stress-resistant function of Burkholderia is important and that trehalose, known as a stress protectant, plays a role in the symbiotic association.

Tuberculosis (TB) is an old disease caused by Mycobacterium tuberculosis. Although it has been known for humans for thousands of years, the treatment of this disease still requires a lengthy therapy with multiple antibiotics. Also, the emergence of multidrug-resistant strains made it more difficult to treat TB, calling for a novel treatment approach. In Photodynamic therapy (PDT), a photosensitizer, such as methylene blue (MB), is irradiated by a laser, generating reactive oxygen species and killing microorganisms. Here, using M. smegmatis as a model mycobacterium, we examined the utility of PDT in TB treatment. The photosensitizer MB alone showed weak antimicrobial activity; however, when irradiated by a laser, it efficiently killed M. smegmatis (> 97% killing with 30 mg/ml MB and 54 J/cm 2 irradiation). Surprisingly, PDT showed more efficient killing activity toward drug-resistant strains of M. smegmatis than the drug-sensitive wild-type strain. In PDT, when the irradiation step alone (Intermittent PDT) or the entire PDT process was repeated (Repeated PDT), the bactericidal activity was significantly enhanced. Since PDT can be applied locally in a short period of time and kills mycobacterium irrespective of its antibiotic resistance status, we conclude that PDT can be a viable option for TB treatment.

The blade is a representative artifact of the upper Paleolithic of Korea. The study of the manufacturing techniques of the blade and restoration of it play an important role in understanding of survival skills of upper Paleolithic human. This paper researches into the technology and process of the blade production through the blade production technology we learned from ‘Refitting artifact’ of Imsil Haga site, and analogizes the kind of the hammer which they used for the blade production in comparison with the existing research result of experimental archaeology on the blade production. Restoring the blade production process as a result of the analysis of ‘refitting artifacts’, 1. Shaping, removed cortical face and unnecessary parts of the raw material are made into sizes and shapes suitable for blade production using stone hammer direct percussion (refitting artifacts 1, 3). 2. creation of a striking platform, 3. blade debitage using the Antler hammer direct percussion. (refitting artifacts 1, 3) 4. Change the striking platform according to the production process, and blade debitage by making the most of the stones several times (refitting artifacts 1, 2). 5. When knapping accidents (step, hinge, and flange) appeared on the blade core, or when the size of the core became smaller and it became difficult to make a blade of the desired size, the blade was discarded without production more blades. The reason for the abandonment of the blade was 1. If it is no longer possible to make the blade due to the Knapping accidents (step, plunging, hinged), 2. If the size of the blade cannot be made, The ‘Refitting artifact 1’ includes two tools (tanged point), which analyzed the length and production space of the tool that the tool maker wanted. First of all, considering that the length of the blade identified in ‘Refitting artifact 1’ is about 40 to 88mm, and the tanged point is about 51, 54mm, it is thought that the stone maker made a blade with a length of about 50 to 70mm or made a tool. The excavation location of tanged point is about 2m away from the central part of the bladecore, and it is thought that the tool was made by moving the blade after manufacturing it.

The Gram-positive pathogen Staphylococcus aureus is the only bacterium known to synthesize arginine from proline via the arginine-proline interconversion pathway, despite having genes for the well-conserved glutamate pathway. Since the proline-arginine interconversion pathway is repressed by CcpA-mediated carbon catabolite repression (CCR), CCR has been attributed to the arginine auxotrophy of S. aureus. Using ribose as a secondary carbon source, here, we demonstrate that S. aureus arginine auxotrophy is not due to CCR but due to the inadequate concentration of proline degradation product. Proline is degraded by proline dehydrogenase (PutA) into pyrroline-5-carboxylate (P5C). Although the PutA expression was fully induced by ribose, the P5C concentration remained insufficient to support arginine synthesis because P5C was constantly consumed by the P5C reductase ProC. When the P5C concentration was artificially increased by either PutA overexpression or proC-deletion, S. aureus could synthesize arginine from proline regardless of carbon source. In contrast, when the P5C concentration was reduced by overexpression of proC, it inhibited the growth of the ccpA-deletion mutant without arginine. Intriguingly, the ectopic expression of the glutamate pathway enzymes converted S. aureus into arginine prototroph. In an animal experiment, the arginine-proline interconversion pathway was not required for the survival of S. aureus. Based on these results, we concluded that S. aureus does not synthesize arginine from proline under physiological conditions. We also propose that arginine auxotrophy of S. aureus is not due to the CcpA-mediated CCR but due to the inactivity of the conserved glutamate pathway.

Bacterial DegP has dual functions as a protease and a chaperone and supports bacterial growth under stressful conditions. In symbioses involving bacteria, bacterial symbionts encounter various stressors and may need functional DegP for symbiotic association with the host.