Berberine hydrochloride reduces staphyloxanthin synthesis by inhibiting fni genes in methicillin-resistant Staphylococcus aureus.

BACKGROUND: Methicillin-resistant Staphylococcus aureus (MRSA) poses a great health threat to humans. Looking for compounds that could reduce the resistance of S. aureus towards methicillin is an effective way to alleviate the antimicrobial resistance crisis. METHODS AND RESULTS: Minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), Time-killing growth curve, staphyloxanthin and penicillin-binding protein 2a (PBP2a) were detected. A quantitative polymerase chain reaction was used to measure the effect of BBH on the gene transcription profiles of MRSA. The MIC of MRSA-ST59-t437 towards oxacillin was 8 µg/ml, and MBC was 128 µg/ml. After adding a sub-inhibitory concentration of BBH, the MIC and MBC of MRSA-ST59-t478 towards oxacillin went down to 0.125 and 32 µg/ml respectively. The amount of PBP2a and staphyloxanthin were reduced after treatment with BBH. Moreover, the transcription levels of sarA, mecA and fni genes were downregulated. CONCLUSIONS: It is for the first time reported that BBH could inhibit staphyloxanthin synthesis by inhibiting fni gene. Moreover, fni might be the target gene of sarA, and there might be another regulatory pathway to inhibit staphyloxanthin biosynthesis. BBH could effectively reduce the methicillin resistance of MRSA-ST59-t437 by downregulating fni, sarA and mecA genes.

Influencing factors of corticomuscular coherence in stroke patients.

Stroke, also known as cerebrovascular accident, is an acute cerebrovascular disease with a high incidence, disability rate, and mortality. It can disrupt the interaction between the cerebral cortex and external muscles. Corticomuscular coherence (CMC) is a common and useful method for studying how the cerebral cortex controls muscle activity. CMC can expose functional connections between the cortex and muscle, reflecting the information flow in the motor system. Afferent feedback related to CMC can reveal these functional connections. This paper aims to investigate the factors influencing CMC in stroke patients and provide a comprehensive summary and analysis of the current research in this area. This paper begins by discussing the impact of stroke and the significance of CMC in stroke patients. It then proceeds to elaborate on the mechanism of CMC and its defining formula. Next, the impacts of various factors on CMC in stroke patients were discussed individually. Lastly, this paper addresses current challenges and future prospects for CMC.

Causal link between prefrontal cortex and EEG microstates: evidence from patients with prefrontal lesion.

Introduction: At present, elucidating the cortical origin of EEG microstates is a research hotspot in the field of EEG. Previous studies have suggested that the prefrontal cortex is closely related to EEG microstate C and D, but whether there is a causal link between the prefrontal cortex and microstate C or D remains unclear. Methods: In this study, pretrial EEG data were collected from ten patients with prefrontal lesions (mainly located in inferior and middle frontal gyrus) and fourteen matched healthy controls, and EEG microstate analysis was applied. Results: Our results showed that four classical EEG microstate topographies were obtained in both groups, but microstate C topography in patient group was obviously abnormal. Compared to healthy controls, the average coverage and occurrence of microstate C significantly reduced. In addition, the transition probability from microstate A to C and from microstate B to C in patient group was significantly lower than those of healthy controls. Discussion: The above results demonstrated that the damage of prefrontal cortex especially inferior and middle frontal gyrus could lead to abnormalities in the spatial distribution and temporal dynamics of microstate C not D, showing that there is a causal link between the inferior and middle frontal gyrus and the microstate C. The significance of our findings lies in providing new evidence for elucidating the cortical origin of microstate C.

Metabolic engineering of Zymomonas mobilis for anaerobic isobutanol production.

BACKGROUND: Biofuels and value-added biochemicals derived from renewable biomass via biochemical conversion have attracted considerable attention to meet global sustainable energy and environmental goals. Isobutanol is a four-carbon alcohol with many advantages that make it attractive as a fossil-fuel alternative. Zymomonas mobilis is a highly efficient, anaerobic, ethanologenic bacterium making it a promising industrial platform for use in a biorefinery. RESULTS: In this study, the effect of isobutanol on Z. mobilis was investigated, and various isobutanol-producing recombinant strains were constructed. The results showed that the Z. mobilis parental strain was able to grow in the presence of isobutanol below 12 g/L while concentrations greater than 16 g/L inhibited cell growth. Integration of the heterologous gene encoding 2-ketoisovalerate decarboxylase such as kdcA from Lactococcus lactis is required for isobutanol production in Z. mobilis. Moreover, isobutanol production increased from nearly zero to 100-150 mg/L in recombinant strains containing the kdcA gene driven by the tetracycline-inducible promoter Ptet. In addition, we determined that overexpression of a heterologous als gene and two native genes (ilvC and ilvD) involved in valine metabolism in a recombinant Z. mobilis strain expressing kdcA can divert pyruvate from ethanol production to isobutanol biosynthesis. This engineering improved isobutanol production to above 1 g/L. Finally, recombinant strains containing both a synthetic operon, als-ilvC-ilvD, driven by Ptet and the kdcA gene driven by the constitutive strong promoter, Pgap, were determined to greatly enhance isobutanol production with a maximum titer about 4.0 g/L. Finally, isobutanol production was negatively affected by aeration with more isobutanol being produced in more poorly aerated flasks. CONCLUSIONS: This study demonstrated that overexpression of kdcA in combination with a synthetic heterologous operon, als-ilvC-ilvD, is crucial for diverting pyruvate from ethanol production for enhanced isobutanol biosynthesis. Moreover, this study also provides a strategy for harnessing the valine metabolic pathway for future production of other pyruvate-derived biochemicals in Z. mobilis.

Establishment and application of a CRISPR-Cas12a assisted genome-editing system in Zymomonas mobilis.

BACKGROUND: Efficient and convenient genome-editing toolkits can expedite genomic research and strain improvement for desirable phenotypes. Zymomonas mobilis is a highly efficient ethanol-producing bacterium with a small genome size and desirable industrial characteristics, which makes it a promising chassis for biorefinery and synthetic biology studies. While classical techniques for genetic manipulation are available for Z. mobilis, efficient genetic engineering toolkits enabling rapidly systematic and high-throughput genome editing in Z. mobilis are still lacking. RESULTS: Using Cas12a (Cpf1) from Francisella novicida, a recombinant strain with inducible cas12a expression for genome editing was constructed in Z. mobilis ZM4, which can be used to mediate RNA-guided DNA cleavage at targeted genomic loci. gRNAs were then designed targeting the replicons of native plasmids of ZM4 with about 100% curing efficiency for three native plasmids. In addition, CRISPR-Cas12a recombineering was used to promote gene deletion and insertion in one step efficiently and precisely with efficiency up to 90%. Combined with single-stranded DNA (ssDNA), CRISPR-Cas12a system was also applied to introduce minor nucleotide modification precisely into the genome with high fidelity. Furthermore, the CRISPR-Cas12a system was employed to introduce a heterologous lactate dehydrogenase into Z. mobilis with a recombinant lactate-producing strain constructed. CONCLUSIONS: This study applied CRISPR-Cas12a in Z. mobilis and established a genome editing tool for efficient and convenient genome engineering in Z. mobilis including plasmid curing, gene deletion and insertion, as well as nucleotide substitution, which can also be employed for metabolic engineering to help divert the carbon flux from ethanol production to other products such as lactate demonstrated in this work. The CRISPR-Cas12a system established in this study thus provides a versatile and powerful genome-editing tool in Z. mobilis for functional genomic research, strain improvement, as well as synthetic microbial chassis development for economic biochemical production.