Preparation and Methicillin-Resistant Staphylococcus aureus Biofilm Elimination Effect of Baicalein-Loaded Hyaluronic acid/β-Cyclodextrin grafted Chitosan Nanoparticles

Methicillin-resistant Staphylococcus aureus(MRSA)is a common pathogen causing acquired infections.Antibiotics are routinely employed for bacterial infection treatment.Excessive antibiotic use for bacterial infections heightens resistance,and MRSA resistance is being prevalent[1].MRSA exhibits substantial resistance to conventional antibiotics,which is associated with its biofilm-forming capability.The bacterial biofilm serves as a barrier,restricting nutrient access and slowing internal metabolism,increasing antibiotic resistance.The bacterial biofilm forms a defensive layer,resisting antibiotic penetration while preventing nutrient entry,inducing a slow bacterial metabolism,and increasing bacterial resistance[2].Consequently,biofilm formation and the emergence of resistance to conventional antibiotics have become substantial challenges in the field of infectious diseases.The development of agents to remove biofilm barriers is urgently required because biofilms are extremely hazardous.

Pore shrinkage capacity of Shajiang black soils(Vertisols)on the North China Plain and its influencing factors

Different pore sizes present different pore shrinkage capacities in a nonrigid soil.However,the shrinkage capacities of different pore sizes and their influencing factors are not clear.We aimed to quantify the shrinkage capacities of different pore sizes(large pores,>50μm;medium pores,0.2-50μm;fine pores,<0.2μm)and determine how soil properties impact soil shrinkage capacity at the regional scale.Two sampling transects from west to east(360 km long,35 samples)and from north to south(190 km long,29 samples)were selected to investigate soil shrinkage capacity and physicochemical properties of at0-20 cm depth in the Vertisol(locally known as Shajiang black soil)region of the North China Plain.The results showed that soil total shrinkage capacity,indicated by the coefficient of linear extensibility(COLE),had a mean value of 0.041-0.051 in the west-east and north-south transects.Large pores had higher pore shrinkage index(PSI)values(0.103-0.109)than medium(0.077-0.096)and fine(0.087-0.091)pores.The PSI of fine pores showed a fluctuating increasing trend from northwest to southeast,and the fine pore shrinkage capacity determined the COLE(r^(2)=0.789,P<0.001).The PSI of large pores had a significant relationship with soil bulk density(r=0.281,P<0.05)and organic carbon(r=-0.311,P<0.05),whereas those of medium and fine pores were correlated with soil clay content(r=0.381 and 0.687,respectively,P<0.001).In addition,the PSI of fine pores was also correlated with montmorillonite content(r=0.387,P<0.01).It can be concluded that the PSI of large pores is related to anthropogenically influenced soil properties with low stability,whereas those of medium and fine pores are related to pedogenic properties.The high variability in anthropogenic and pedogenic factors explains the spatial pattern of Vertisol shrinkage capacity on the North China Plain.

Nitrogen fertilization degrades soil aggregation by increasing ammonium ions and decreasing biological binding agents on a Vertisol after 12 years

Degraded soil aggregation arising from nitrogen(N)fertilization has been reported in many studies;however,the mechanisms have not yet been clarified.Elucidating the impact of N fertilization on soil aggregation would help to improve soil structure and sustain high crop production.The objective of this study was to determine the impact of long-term N fertilization on soil aggregation and its association with binding and dispersing agents.A 12-year(2008–2019)N fertilization field experiment on a Vertisol was performed,covering a wide range of N application rates(0,360,450,540,630,and 720 kg ha-1 year-1)and including straw management(straw return and straw removal)in a wheat(Triticum aestivum L.)-maize(Zea mays L.)cropping system.Soil samples of 0–20 cm depth were collected from 12 field treatments with 3 replications in 2019.Soil aggregate stability(mean weight diameter(MWD))and contents of soil organic carbon(SOC),glomalin-related soil protein(GRSP),microbial biomass carbon(MBC),and mineral N(NH4+and NO3-)were determined.Long-term N fertilization under straw removal conditions reduced soil MWD by 12%–18%at N rates from 0 to 720 kg ha-1 compared to that under straw return(P<0.05).Soil MWD was positively associated with pH(P<0.05)and MBC(P<0.05),but negatively correlated with NH4+(P<0.05)and NO3-(P<0.05).Compared with the straw removal treatment,the straw incorporation treatment significantly improved the contents of aggregating agents(SOC,GRSP,and MBC)(P<0.001),but did not affect that of the dispersing agent(NH4+)(P>0.05);consequently,it improved soil aggregation.Overall,our results indicate that long-term N fertilization may degrade soil aggregation because of the increases in monovalent ions(H+and NH4+)and the decrease in MBC during soil acidification,especially when the applied N dose exceeded 360 kg ha-1 year-1.Our finding can minimize the negative structural impacts on Vertisol.