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Actinobacteria are ubiquitous bacteria undergoing complex developmental transitions coinciding with antibiotic production in response to stress or nutrient starvation. This transition is mainly controlled by the interaction between the second messenger c-di-GMP and the master repressor BldD. To date, the upstream factors and the global signal networks that regulate these intriguing cell biological processes remain unknown. In Saccharopolyspora erythraea, we found that acetyl phosphate (AcP) accumulation resulting from environmental nitrogen stress participated in the regulation of BldD activity through cooperation with c-di-GMP. AcP-induced acetylation of BldD at K11 caused the BldD dimer to fall apart and dissociate from the target DNA and disrupted the signal transduction of c-di-GMP, thus governing both developmental transition and antibiotic production. Additionally, practical mutation of BldDK11R bypassing acetylation regulation could enhance the positive effect of BldD on antibiotic production. The study of AcP-dependent acetylation is usually confined to the control of enzyme activity. Our finding represents an entirely different role of the covalent modification caused by AcP, which integrated with c-di-GMP signal in modulating the activity of BldD for development and antibiotic production, coping with environmental stress. This coherent regulatory network might be widespread across actinobacteria, thus has broad implications., (© The Author(s) 2023. Published by Oxford University Press on behalf of Nucleic Acids Research.)

Background: Mycoplasma pneumoniae is a common pathogen that caused community-acquired pneumonia (CAP). P1 protein served as major adhesion and immunodominant protein in Mycoplasma pneumoniae, but little about P1 gene was learned and the relationship between P1 genotype and macrolide resistance has yet to be explored., Methods: The DNA sequence of the entire P1 gene from 35 strains isolated from clinical specimens collected in Beijing, China, in 2010 was determined. The resulting sequences were checked for known macrolide resistance mutations, such as A2063G, A2064G, C2617G in domain V of 23S rRNA. Antibiotic susceptibility test was done to further identify macrolide resistant strains., Results: Thirty-four clinical strains were type 1, and were identical to type 1 reference strain MP129. Only one clinical strain, MpYYM22, was type 2, and proved to be variant 2c. One synonymous point mutation in the P1 type 1 gene from two isolates was identified relative to the MP129 P1 sequence at nucleotide position (nt) 552 (C>A), while another two isolates had missense mutations at nt 2504 (G>A). This point mutation caused an amino acid change from glycine to glutamic acid. An AGT tri-nucleotide variable-number tandem repeat (VNTR), coding for serine and repeating 6-11 times, up to 15-16 times, was found in the region between the RepMP4 and RepMP2/3 elements in the 35 isolates examined. All 35 clinical strains, including MpYYM22, demonstrated macrolide resistance with the range of minimum inhibitory concentration (MIC) of erythromycin from 64 to 256 µg/ml, having an A2063G transition in domain V of the 23S rRNA gene., Conclusions: P1 type 1 was the dominant type of Mycoplasma pneumoniae in Beijing in 2010, although variant 2c strains were present. More samples are needed to determine whether there is a relationship between the P1 genotype and macrolide resistance, as the 35 strains examined did not allow a conclusive result. However, the AGT tri-nucleotide VNTR may be a more informative locus for multi-locus VNTR analysis.

Objective: To develop antibacterial coatings for orthopedic implants with a sustained release of drugs., Methods: Wollastonite coatings were deposited on the titanium substrates by an atmospheric plasma spray system. After soaking in weight percent of 5% AgNO(3) solution for 24 h, the wollastonite coatings loading silver were obtained. Gentamicin were loaded on the wollastonite coatings by collagen grafting process. The release rates of drugs from wollastonite coatings were investigated by the in vitro solution soaking test. One strain of S. aureus was used in zone of inhibition test to evaluate the antibacterial properties of drug loaded wollastonite coatings, and the cell culture test was used to evaluate their cytotoxicity., Results: Silver and gentamicin loaded wollastonite coatings were successfully prepared. The release of silver ions from the silver loaded wollastonite coatings lasted 50 d in deionized water, effectively inhibiting the growth of S. aureus for 40 d. While an initial burst release of gentamicin was found during the in vitro solution soaking test. The gentamicin released from gentamicin loaded wollastonite coatings can inhibit the growth of S. aureus for 18 d. Both the two kinds of antibacterial wollastonite coatings showed no adverse effect on cellular adhesion, proliferation and alkaline phosphatase expression., Conclusions: Compared with gentamicin loaded wollastonite coatings, silver loaded wollastonite coatings may have more promising clinical applications due to the even and long-time antibacterial agent release.

Objective: To study the preparation and characteristics of silver-loaded nano-titania coating so as to develop a bioactive implant material with antibacterial property., Methods: Plasma sprayed nano-titania coatings were immersed in 1%, 5%, and 9% AgNO3 solution to load silver. The loaded silver and its distribution were evaluated by scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS). After optimizing the preparation process, the release rate of silver from the nano-titania coating was measured in deionized water, its corresponding in vitro cytotoxicity and antibacterial activity were also examined., Results: The loaded silver was in proper quantity and distributed evenly on the nano-titania coatings after immersion in 5% AgNO3. A burst release of the silver could be detected. The quick release of silver from the titania coatings sustained about 12 days in deionized water, which had no obvious influence on the surface morphology of titania coatings. The loaded silver did not inhibit the osteoblast proliferation (P = 0.1) and alkaline phosphatase expression (P = 0.06), however, it effectively inhibited the survival and growth of Staphylococcus aureus for 12 days: the zone of inhibition reached 3.81 +/- 0.8 mm with a bacteria killing rate of 100%., Conclusions: It is economical and effective to prepare the silver-loaded nano-titania coatings by 5% AgNO3 solution. The loaded silver has good antibacterial function, and shows no obvious effect on the physical and biological properties of nano-titania coatings.