The prevalence of stomatitis, especially that caused by
Candida albicans
, has highlighted the need for new antifungal agents. We previously found that a type of quaternary ammonium salts, ...dimethylaminododecyl methacrylate (DMADDM), incorporated in dental materials inhibited the growth and hyphal development of
C. albicans
. However, how the quaternary ammonium salts inhibited the fungal pathogens and whether the oral condition, such as salivary pH variation under different diseases, can affect the antimicrobial capacity of quaternary ammonium salts is unknown. This study evaluated the antifungal effects of DMADDM at different pH in vitro and in vivo. A pH-dependent antifungal effect of DMADDM was observed in planktonic and biofilm growth. DMADDM enhanced antifungal activity at alkaline pH. Two pH-regulated genes (
PHR1/PHR2
) of
C. albicans
were correlated with the pH-dependent antifungal effects of DMADDM. The
PHR1/PHR2
genes and pH values regulated the zeta potential of
C. albicans
, which then influenced the binding between
C. albicans
cells and DMADDM. The pH-dependent antifungal activity of DMADDM was then substantiated in a murine oropharyngeal candidiasis model. We directly demonstrated that the antifungal abilities of quaternary ammonium salts relied on the cell zeta potential which affected the binding between fungal cells and quaternary ammonium salts. These findings suggest a new antifungal mechanism of quaternary ammonium under different pH and that DMADDM can be a potential antifungal agent applied in dental materials and stomatitis therapy.
Key Points
• DMADDM has stronger antifungal activity in alkaline than in acidic pH conditions.
• The pH values and pH-regulated genes can affect the zeta potential of fungal cells.
• Zeta potential of fungal cells directly affect the binding between DMADDM and cells.
Graphical abstract
Schematic diagram of the antifungal activities of DMADDM at different pH values
The present study focused on the design and preparation of acid-responsive benzimidazole-chitosan quaternary ammonium salt (BIMIXHAC) nanogels for a controlled, slow-release of Doxorubicin HCl ...(DOX.HCl). The BIMIXHAC was crosslinked with sodium tripolyphosphate (TPP) using the ion crosslinking method. The method resulted in nanogels with low polydispersity index, small particle size, and positive zeta potential values, indicating the good stability of the nanogels. Compared to hydroxypropyl trimethyl ammonium chloride chitosan-Doxorubicin HCl-sodium tripolyphosphate (HACC-D-TPP) nanogel, the benzimidazole-chitosan quaternary ammonium salt-Doxorubicin HCl-sodium tripolyphosphate (BIMIXHAC-D-TPP) nanogel show higher drug encapsulation efficiency and loading capacity (BIMIXHAC-D-TPP 93.17 ± 0.27% and 31.17 ± 0.09%), with acid-responsive release profiles and accelerated release in vitro. The hydroxypropyl trimethyl ammonium chloride chitosan-sodium tripolyphosphate (HACC-TPP), and benzimidazole-chitosan quaternary ammonium salt-sodium tripolyphosphate (BIMIXHAC-TPP) nanogels demonstrated favorable antioxidant capability. The assay of cell viability, measured by the MTT assay, revealed that nanogels led to a significant reduction in the cell viability of two cancer cells: the human lung adenocarcinoma epithelial cell line (A549) and the human breast cancer cell line (MCF-7). Furthermore, the BIMIXHAC-D-TPP nanogel was 2.96 times less toxic than DOX.HCl to the mouse fibroblast cell line (L929). It was indicated that the BIMIXHAC-based nanogel with enhanced antioxidant and antitumor activities and acidic-responsive release could serve as a potential nanocarrier.
The emergence of antibiotic resistance genes (ARGs) in microbes can be largely attributed to the abuse and misuse of antibiotics and biocides. Quaternary ammonium compounds (QACs) have been used ...worldwide as common disinfectants and detergents; however, their potential impact on the spread and diffusion of ARGs is still unknown. In this study, we detected the QAC resistance gene (
qacEΔ1
), the 1 integron gene (
intI1
), and 12 ARGs (
sul1
,
sul2
,
cfr
,
cml
,
fexA
,
tetA
,
tetG
,
tetQ
,
tetX
,
ermB
,
bla
TEM
,
and
dfrA1
) in 48 water samples from three watersheds by quantitative PCR (qPCR). We investigated the evolution of bacterial antibiotic resistance under QAC and antibiotic environmental pressures by long-term continuous culture. In addition, five QACs were selected to investigate the effect of QAC on the efficiency of conjugation transfer. The changes in bacterial cell membrane and production of reactive oxygen species (ROS) were detected by flow cytometry, revealing the mechanism by which QAC affects the spread of antibiotic resistance. Our results showed that the QAC resistance gene was ubiquitous in watersheds and it had significant correlation with
intI1
and seven ARGs (
r
= 0.999,
p
< 0.01). QACs could increase the resistance of bacteria to multiple antibiotics. Furthermore, all five QACs promoted the conjugation transfer of the RP4 plasmid; the optimal concentration of QACs was about 10
−1
–10
−2
mg/L and their transfer efficiencies were between 1.33 × 10
−6
and 8.87 × 10
−5
. QACs enhanced membrane permeability of bacterial cells and stimulated bacteria to produce ROS, which potentially promoted the transfer of plasmids between bacteria. In conclusion, this study demonstrated that QACs may facilitate the evolution and gene transfer of antibiotic resistance gene among microbiome.
Nitric oxide (NO) has important functions in biology and atmospheric chemistry as a toxin, signaling molecule, ozone depleting agent and the precursor of the greenhouse gas nitrous oxide (N
O). ...Although NO is a potent oxidant, and was available on Earth earlier than oxygen, it is unclear whether NO can be used by microorganisms for growth. Anaerobic ammonium-oxidizing (anammox) bacteria couple nitrite reduction to ammonium oxidation with NO and hydrazine as intermediates, and produce N
and nitrate. Here, we show that the anammox bacterium Kuenenia stuttgartiensis is able to grow in the absence of nitrite by coupling ammonium oxidation to NO reduction, and produce only N
. Under these growth conditions, the transcription of proteins necessary for NO generation is downregulated. Our work has potential implications in the control of N
O and NO emissions from natural and manmade ecosystems, where anammox bacteria contribute significantly to N
release to the atmosphere. We hypothesize that microbial NO-dependent ammonium oxidation may have existed on early Earth.
A Single Particle Aerosol Mass Spectrometer (SPAMS), a Single Particle Soot Photometer (SP2) and various meteorological instruments were employed to investigate the chemical and physical properties ...of black carbon (BC) aerosols during a regional air pollution episode in urban Shanghai over a 5-day period in December 2013. The refractory black carbon (rBC) mass concentrations measured by SP2 averaged 3.2 µg m−3, with the peak value of 12.1 µg m−3 at 04:26 LT on 7 December. The number of BC-containing particles captured by SPAMS in the size range 200–1200 nm agreed very well with that detected by SP2 (R2 = 0.87). A cluster analysis of the single particle mass spectra allowed for the separation of BC-containing particles into five major classes: (1) Pure BC; (2) BC attributed to biomass burning (BBBC); (3) K-rich BC-containing (KBC); (4) BC internally mixed with OC and ammonium sulfate (BCOC-SOx); (5) BC internally mixed with OC and ammonium nitrate (BCOC-NOx). The size distribution of internally mixed BC particles was bimodal. Detected by SP2, the condensation mode peaked around ∼ 230 nm and droplet mode peaked around ∼ 380 nm, with a clear valley in the size distribution around ∼ 320 nm. The condensation mode mainly consisted of traffic emissions, with particles featuring a small rBC core (∼ 60–80 nm) and a relatively thin absolute coating thickness (ACT, ∼ 50–130 nm). The droplet mode included highly aged traffic emission particles and biomass burning particles. The biomass burning particles had a larger rBC core (∼ 80–130 nm) and a thick ACT (∼ 110–300 nm). The highly aged traffic emissions had a smaller core (∼ 60–80 nm) and a very thick ACT (∼ 130–300 nm), which is larger than reported in any previous literature. A fast growth rate (∼ 20 nm h−1) of rBC with small core sizes was observed during the experiment. High concentrations pollutants like NO2 likely accelerated the aging process and resulted in a continuous size growth of rBC-containing particles from traffic emission.
Root development is strongly affected by the plant's nutritional status and the external availability of nutrients. Employing split-root systems, we show here that local ammonium supply to ...Arabidopsis thaliana plants increases lateral root initiation and higher-order lateral root branching, whereas the elongation of lateral roots is stimulated mainly by nitrate. Ammonium-stimulated lateral root number or density decreased after ammonium or Gln supply to a separate root fraction and did not correlate with cumulative uptake of ¹⁵N-labeled ammonium, suggesting that lateral root branching was not purely due to a nutritional effect but most likely is a response to a sensing event. Ammonium-induced lateral root branching was almost absent in a quadruple AMMONIUM TRANSPORTER (qko, the amt1;1 amt1;2 amt1;3 amt2;1 mutant) insertion line and significantly lower in the amt1;3-1 mutant than in the wild type. Reconstitution of AMT1;3 expression in the amt1;3-1 or in the qko background restored higher-order lateral root development. By contrast, AMT1;1, which shares similar transport properties with AMT1;3, did not confer significant higher-order lateral root proliferation. These results show that ammonium is complementary to nitrate in shaping lateral root development and that stimulation of lateral root branching by ammonium occurs in an AMT1;3-dependent manner.
Hydrogels, possessing high biocompatibility and adaptability to biological tissue, show great usability in medical applications. In this research, a series of novel cross-linked chitosan quaternary ...ammonium salt loading with gentamicin sulfate (CTMCSG) hydrogel films with different cross-linking degrees were successfully obtained by the reaction of chitosan quaternary ammonium salt (TMCS) and epichlorohydrin. Fourier transform infrared spectroscopy (FTIR), thermal analysis, and scanning electron microscope (SEM) were used to characterize the chemical structure and surface morphology of CTMCSG hydrogel films. The physicochemical property, gentamicin sulphate release behavior, cytotoxicity, and antibacterial activity of the CTMCSG against
and
were determined. Experimental results demonstrated that CTMCSG hydrogel films exhibited good water stability, thermal stability, drug release capacity, as well as antibacterial property. The inhibition zone of CTMCSG hydrogel films against
and
could be up to about 30 mm. Specifically, the increases in maximum decomposition temperature, mechanical property, water content, swelling degree, and a reduction in water vapor permeability of the hydrogel films were observed as the amount of the cross-linking agent increased. The results indicated that the CTMCSG-4 hydrogel film with an interesting physicochemical property, admirable antibacterial activity, and slight cytotoxicity showed the potential value as excellent antibacterial wound dressing.
Palm biodiesel from crude palm oil (CPO) was prepared via transesterification in a two-stage process using acidic ionic liquid as first step catalyst as opposed to using directly the ...alkaline-catalyzed transesterification which was found to be unsuitable. The esterification of the free fatty acids (FFA) of the CPO was carried out using triethylammonium hydrogensulfate (Et3NHSO4) as the pre-catalyst in the first stage, in which the acid value was reduced from 6.98 to 1.24 mg KOH/g of oil followed by the use of KOH-catalyzed transesterification in the second stage. The effects of molar ratio of methanol to crude palm oil feed, the amount of ionic liquid and the reaction temperature were evaluated for the percent conversion of FFA. The conversion rate of FFA attained was 82.1% when 5.2 wt.% of Et3NHSO4 was used for the reaction of methanol with CPO at a ratio of 15: 1 respectively, and at reaction temperature of 170 degree C for 3 h. The second alkali-catalyze step was performed under agitation with stirrer speed of 600 rpm at 60 degree C using 1.0% KOH for 50 min. The final biodiesel product was analyzed using gas chromatography (GC) with a reaction yield of 96.9%. The density, kinematic viscosity, acid value, ester content and other properties of the biodiesel sample were also measured and compared to the ASTM and the European biodiesel specifications.
The nitrate to ammonium ratios in nitrogen (N) compounds in wet atmospheric deposits have increased over the recent past, which is a cause for some concern as the individual effects of nitrate and ...ammonium deposition on the biomass of different soil microbial communities and enzyme activities are still poorly defined. We established a field experiment and applied ammonium (NH4Cl) and nitrate (NaNO3) at monthly intervals over a period of 4 years. We collected soil samples from the ammonium and nitrate treatments and control plots in three different seasons, namely spring, summer, and fall, to evaluate the how the biomass of different soil microbial communities and enzyme activities responded to the ammonium (NH4Cl) and nitrate (NaNO3) applications. Our results showed that the total contents of phospholipid fatty acids (PLFAs) decreased by 24 and 11 % in the ammonium and nitrate treatments, respectively. The inhibitory effects of ammonium on Gram-positive bacteria (G+) and bacteria, fungi, actinomycetes, and arbuscular mycorrhizal fungi (AMF) PLFA contents ranged from 14 to 40 % across the three seasons. We also observed that the absolute activities of C, N, and P hydrolyses and oxidases were inhibited by ammonium and nitrate, but that nitrate had stronger inhibitory effects on the activities of acid phosphatase (AP) than ammonium. The activities of N-acquisition specific enzymes (enzyme activities normalized by total PLFA contents) were about 21 and 43 % lower in the ammonium and nitrate treatments than in the control, respectively. However, the activities of P-acquisition specific enzymes were about 19 % higher in the ammonium treatment than in the control. Using redundancy analysis (RDA), we found that the measured C, N, and P hydrolysis and polyphenol oxidase (PPO) activities were positively correlated with the soil pH and ammonium contents, but were negatively correlated with the nitrate contents. The PLFA biomarker contents were positively correlated with soil pH, soil organic carbon (SOC), and total N contents, but were negatively correlated with the ammonium contents. The soil enzyme activities varied seasonally, and were highest in March and lowest in October. In contrast, the contents of the microbial PLFA biomarkers were higher in October than in March and June. Ammonium may inhibit the contents of PLFA biomarkers more strongly than nitrate because of acidification. This study has provided useful information about the effects of ammonium and nitrate on soil microbial communities and enzyme activities.
Arbuscular mycorrhizal (AM) fungi contribute to plant nitrogen (N) acquisition. Recent studies demonstrated the transport of N in the form of ammonium during AM symbiosis. Here, we hypothesize that ...induction of specific ammonium transporter (AMT) genes in Sorghum bicolor during AM colonization might play a key role in the functionality of the symbiosis.
For the first time, combining a split-root experiment and microdissection technology, we were able to assess the precise expression pattern of two AM-inducible AMTs, SbAMT3;1 and SbAMT4. Immunolocalization was used to localize the protein of SbAMT3;1.
The expression of SbAMT3;1 and SbAMT4 was greatly induced locally in root cells containing arbuscules and in adjacent cells. However, a split-root experiment revealed that this induction was not systemic. By contrast, a strictly AM-induced phosphate transporter (SbPt11) was expressed systemically in the split-root experiment. However, a gradient of expression was apparent. Immunolocalization analyses demonstrated that SbAMT3;1 was present only in cells containing developing arbuscules.
Our results show that the SbAMT3;1 and SbAMT4 genes are expressed in root cortical cells, which makes them ready to accommodate arbuscules, a process of considerable importance in view of the short life span of arbuscules. Additionally, SbAMT3;1 might play an important role in N transfer during AM symbiosis.
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