Archives of Microbiology最新文献

Natural antimicrobial peptides frequently exhibit characteristic terminal features, such as a free amino group at the N-terminus and C-terminal amidation, that are believed to enhance antimicrobial performance. However, the molecular rationale underlying this evolutionarily favored structural motif remains insufficiently understood. In this study, we systematically investigated the influence of terminal capping on Mastoparan C (MPC), a representative helical amphipathic peptide, by combining structural and biological evaluation with molecular dynamics (MD) simulations. Our findings indicate that this common structural motif of terminal modifications in antimicrobial peptides is a strategic adaptation to optimize functional performance, enhancing the ability of these peptides to effectively disrupt microbial membranes while maintaining selectivity. This study not only provides insight into the evolutionary design of antimicrobial peptides but also guides the development of synthetic analogs for therapeutic applications. Impact of terminal capping design on antimicrobial peptide: Three analogs of Mastoparan C (H-MPC-NH2) were prepared with the same sequence but different terminal capping groups. We demonstrated that the free amino group at N-terminal and amidated C-terminal gave the best in improving antibacterial potency and selectivity, thus providing insights into the reason this terminal capping design is popular in antimicrobial peptides.

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Staphylococcus epidermidis plays a crucial role in maintaining the skin immunity barrier. However, when host immunity is compromised, it can also lead to skin infections and bloodstream infections. Staphylococcal lipases contribute to bacterial growth, detoxification, and immune evasion, while their esterification capabilities also give them potential biotechnological applications. S. epidermidis secretes at least two lipases, GehC and GehD, which are indirectly regulated by the global regulators Agr and SarA. SarZ, a transcription factor of the SarA family, regulates the expression of various exoproteins, but its role in regulation of lipase synthesis remains unknown. A sarZ gene knockout strain of S. epidermidis previously constructed was utilized in this study. First, lipase activity was found to be significantly elevated in the sarZ mutant relative to the wild-type strain, as determined by both the olive oil agar plate assay and the p-nitrophenol assay. Subsequently, qRT-PCR experiments revealed that SarZ controls the transcription of gehC and gehD divergently. Furthermore, electrophoretic mobility shift assay experiments demonstrated that the recombinant SarZ protein can directly bind to the promoter regions of gehC and gehD. These findings demonstrate that SarZ negatively regulates lipase activity by directly modulating expression of lipase genes, providing a basis for further understanding the regulatory mechanism of lipase production in S. epidermidis.

Among bacterial infections, urinary tract infections (UTIs) remain the most prevalent worldwide and are increasingly challenging to manage due to antibiotic resistance and recurrent inflammation. Caryota mitis L. (C. mitis), locally known as the Fishtail plant, has traditionally been used to treat various disease elements. It has been reported to possess antioxidant, antimicrobial, and anti-inflammatory properties; however, its use in treating UTI-associated pathogens and inflammation remains unexplored. Thus, we aimed to evaluate the anti-inflammatory and antibacterial potential of the methanol extract of C. mitis leaves. GC-MS was initially used for characterisation of C. mitis extract, followed by in-vitro anti-inflammatory (LPS-induced human urinary bladder epithelial T24 cells) and anti-bacterial activity against UTI pathogens (E. coli, K. pneumoniae, Pseudomonas spp., Enterobacter spp., and Proteus mirabilis) was investigated. The C. mitis extract significantly reduces levels of inflammatory cytokines and inhibits all tested uropathogens in a dose-dependent manner. This study highlights C. mitis as a promising adjunct natural therapeutic candidate for managing UTIs.

Diverse studies have indicated that fungal growth and enzyme yields are often greater in solid-state fermentation (SSF) than in submerged fermentation (SmF). To understand the advantages of SSF over SmF, the secretomes of Aspergillus brasiliensis cultured with different sucrose concentrations were analyzed. Secretomic analysis revealed that sucrose induced the production of several polysaccharide-degrading enzymes, and that the secretome of SSF was more complex. Approximately 90% of the secreted proteins in SmF were via signal peptide-mediated mechanisms. However, increasing the sucrose concentration in SSF reduced this to less than 50%, suggesting the presence of alternative secretion mechanisms. Protein fold-change analysis revealed that certain proteins were induced by high sucrose in both cultures. Nevertheless, the relative abundance (RA) was higher under SSF. The production of some extracellular enzymes in both culture types confirmed the absence of catabolic repression mainly in SSF, where invertase and inulinase production were 1.5 and 2.1-fold higher than in SmF, respectively. Thus, SSF provides an environment that facilitates A. brasiliensis growth with minimal constraints from catabolite repression or substrate inhibition. This is due to the diversity of proteins secreted through both conventional and unconventional mechanisms, highlighting the similarity of SSF to the natural fungal habitat.