Coordinated response of phospholipids and acyl components of membrane lipids in Pseudomonas putida A (ATCC 12633) under stress caused by cationic surfactants

Biocides in the Hospital Environment: Application and Tolerance Development

Hospital-acquired infections are a rising problem with consequences for patients, hospitals, and health care workers. Biocides can be employed to prevent these infections, contributing to eliminate or reduce microorganisms' concentrations at the hospital environment. These antimicrobials belong to several groups, each with distinct characteristics that need to be taken into account in their selection for specific applications. Moreover, their activity is influenced by many factors, such as compound concentration and the presence of organic matter. This article aims to review some of the chemical biocides available for hospital infection control, as well as the main factors that influence their efficacy and promote susceptibility decreases, with the purpose to contribute for reducing misusage and consequently for preventing the development of resistance to these antimicrobials.

Morphological and structural response of Bacillus sp. SFC 500-1E after Cr(VI) and phenol treatment

Bacillus sp. SFC 500-1E, a bacterial strain isolated from tannery sediments, is able to remove Cr(VI) and simultaneously tolerate high concentrations of phenol. In this study, we used high-resolution microscopies, fluorescence polarization techniques, and several biochemical approaches to improve our understanding about the adaptive mechanisms of this strain to survive in the presence of Cr(VI) and phenol, both individually and simultaneously. Among adaptive strategies developed by Bacillus sp. SFC 500-1E, an increase in bacterial size, such as length, width, and height, and ultrastructural alterations, such as electron-dense precipitates, the presence of exopolymers, and cell lysis, are noteworthy. The exopolymers observed were consistent with the extensive biofilm formation and exopolysaccharides and extracellular protein quantification. At the cell membrane level, a rapid rigidity was induced in Cr(VI) + phenol treatment. This effect was counteracted after 16 h by changes at the level of phospholipids, mainly in the composition of fatty acids (FAs); in particular, an increase in the unsaturated fatty acid/saturated fatty acid ratio was detected. This study shows evidence of some adaptive responses displayed by Bacillus sp. SFC 500-1E, which allows it to survive in stressful conditions.

More QACs, more questions: Recent advances in structure activity relationships and hurdles in understanding resistance mechanisms

Quaternary ammonium compounds (QACs) are a class of antimicrobials that have been around for over a century; nevertheless, they have found continued renewal in the structures to which they can be appended. Ranging from antimicrobial polymers to adding novel modes of action to existing antibiotics, QACs have found ongoing use due to their potent properties. However, resistance against QACs has begun to emerge, and the mechanism of resistance is still only partially understood. In this review, we aim to summarize the current state of the field and what is known about the mechanisms of resistance so that the QACs of the future can be designed to be evermore efficacious and utilized to unearth the remaining mysteries that surround bacteria's resistance to them.

Membrane Rigidity and Phosphatidic Acid (PtdOH) Signal: Two Important Events in Acinetobacter guillouiae SFC 500-1A Exposed to Chromium(VI) and Phenol

The remodeling of membrane lipids is a mechanism that allows microorganisms to survive in unfavorable environments such as industrial effluents, which often contain inorganic and organic pollutants, like chromium and phenol. In the present work, we evaluated the effect of Cr(VI) and phenol on the membrane of Acinetobacter guillouiae SFC 500-1A, a bacterial strain isolated from tannery sediments where such pollutants can be found. The presence of lipid kinases and phospholipases and the changes in their activities under exposure to these pollutants were determined. Cr(VI) and Cr(VI) + phenol caused the membrane to become more rigid for up to 16 h after exposure. This could be due to an increase in cardiolipin (Ptd₂ Gro) and a decrease in phosphatidylethanolamine (PtdEtn), which are indicative of more order and rigidity in the membrane. Increased phospholipase A activity (PLA, EC 3.1.1.4) could be responsible for the decrease in PtdEtn levels. Moreover, our results indicate that Cr(VI) and Cr(VI) + phenol trigger the phosphatidic acid (PtdOH) signal. The finding of significantly increased phosphatidylinositol-4-phosphate (PtdIns-4-P) levels means this is likely achieved via PtdIns-PLC/DGK. This report provides the first evidence that A. guillouiae SFC 500-1A is able to sense Cr(VI) and phenol, transduce this signal through changes in the physical state of the membrane, and trigger lipid-signaling events.

Pseudomonas putida Δ9-fatty acid desaturase: Gene cloning, expression, and function in the cationic surfactants stress

Pseudomonas putida counteract the fluidizing effect of cationic surfactants decreasing the content of membrane unsaturated fatty acid (UFA). A Δ9-fatty acid desaturase gene (desA) from P. putida was isolated, cloned, and successfully expressed in Escherichia coli, a Δ9 desaturase deficient organism. desA consists of 1185 bp and codes for 394 amino acids. The deduced amino acid sequence reveals three histidine clusters and a hydropathy profile, typical of membrane-bound desaturases. Validating desA expression in E. coli cells, the amount of palmitoleic acid increased from 2.05 to 7.36%, with the concomitant increase in membrane fluidity (fluorescence polarization value decrease from 0.13 ± 0.03 to 0.09 ± 0.02). Also, when DesA activity was assayed in vivo, the percentage of UFA obtained from exogenous palmitic acid [1-¹⁴ C] increased 10-fold. In contrast, when cells expressing desA were exposed 15 min at sublethal concentration of cationic surfactants, the amount of UFA was 82% lower than that detected in cells non-exposed. Thus, the decrease in UFA content to counteract the fluidizing effect of cationic surfactants can be correlated with reduction of DesA activity.

Genomic and Functional Characterization of Environmental Strains of SDS-Degrading Pseudomonas spp., Providing a Source of New Sulfatases

Biochemical, physiological and genomic comparisons of two Pseudomonas strains, assigned previously to the Pseudomonas jessenii subgroup, which are efficient SDS-degraders were carried out. A GO enrichment analysis showed that the genomes of SDS-degraders encode more genes connected with bacterial cell wall biosynthesis and alkanesulfonate monooxygenase activity than their closest relatives from the P. jessenii subgroup. A transcriptomic analysis of the most promising strain exposed to detergent suggests that although SDS can be later utilized as a carbon source, in early stages it influences cell envelope integrity, causing a global stress response followed by cell wall modification and induction of repair mechanisms. Genomes of the analyzed strains from P. jessenii group encode multiple putative sulfatases and their enzymatic activity was experimentally verified, which led to the identification of three novel enzymes exhibiting activity toward SDS. Two of the novel alkylsulfatases showed their highest activity at pH 8.0 and the temperature of 60°C or 70°C. One of the enzymes retained its activity even after 1 h of incubation at 60°C. Ions like K⁺ and Mg²⁺ enhanced enzymatic activity of both proteins, whereas Cu²⁺ or EDTA had inhibitory effects.

Enhanced oral absorption of pemetrexed by ion-pairing complex formation with deoxycholic acid derivative and multiple nanoemulsion formulations: preparation, characterization, and in vivo oral bioavailability and anticancer effect

Objective

The current study sought to design an oral delivery system of pemetrexed (PMX), a multitargeted antifolate antimetabolite, by enhancing its intestinal membrane permeability.

Materials and methods

PMX was ionically complexed with a permeation enhancer such as N^α-deoxycholyl-l-lysyl-methylester (DCK) and prepared as an amorphous solid dispersion by mixing with dispersants such as 2-hydroxypropyl-beta-cyclodextrin (HP-beta-CD) and poloxamer 188 (P188), forming an HP-beta-CD/PMX/DCK/P188; the complex was incorporated into multiple water-in-oil-in-water nanoemulsions in a supersaturated state (HP-beta-CD/PMX/DCK/P188-NE).

Results

After complex formation, the partition coefficient and in vitro membrane permeability of PMX were markedly increased, but it showed similar cytotoxic and inhibitory effects on cancer cell proliferation/migration. Furthermore, the intestinal membrane permeability and epithelial cell uptake of PMX were synergistically improved after HP-beta-CD/PMX/DCK/P188 was incorporated into a nanoemulsion with a size of 14.5±0.45 nm. The in vitro permeability of HP-beta-CD/PMX/DCK/P188-NE across a Caco-2 cell monolayer was 9.82-fold greater than that of free PMX, which might be attributable to the partitioning of PMX to the epithelial cells being facilitated via specific interaction of DCK with bile acid transporters, as well as the enhanced lipophilicity accompanied by surfactant-induced changes in the intestinal membrane structure and fluidity. Therefore, the oral bioavailability of HP-beta-CD/PMX/DCK/P188-NE in rats was evaluated as 26.8%±2.98% which was 223% higher than that of oral PMX. Moreover, oral HP-beta-CD/PMX/DCK/P188-NE significantly suppressed tumor growth in Lewis lung carcinoma cell-bearing mice, and the tumor volume was maximally inhibited by 61% compared with that in the control group.

Conclusion

These results imply that HP-beta-CD/PMX/DCK/P188-NE is an effective and promising delivery system for enhancing the oral absorption of PMX. Thus, there is the potential for new medical applications, including applications in metronomic cancer treatment.

Quaternary ammonium salt N-(dodecyloxycarboxymethyl)-N,N,N-trimethyl ammonium chloride induced alterations in Saccharomyces cerevisiae physiology

We investigated the influence of the quaternary ammonium salt (QAS) called IM (N-(dodecyloxycarboxymethyl)- N,N,N-trimethyl ammonium chloride) on yeast cells of the parental strain and the IM-resistant mutant (EO25 IMR) growth. The phenotype of this mutant was pleiotropic. The IMR mutant exhibited resistance to ethanol, osmotic shock and oxidative stress, as well as increased sensitivity to UV. Moreover, it was noted that mutant EO25 appears to have an increased resistance to clotrimazole, ketoconazole, fluconazole, nystatin and cycloheximide. It also tolerated growth in the presence of crystal violet, DTT and metals (selenium, tin, arsenic). It was shown that the presence of IM decreased ergosterol level in mutant plasma membrane and increased its unsaturation. These results indicate changes in the cell lipid composition. Western blot analysis showed the induction of Pma1 level by IM. RT-PCR revealed an increased PMA1 expression after IM treatment.

Novel nanoemulsion based lipid nanosystems for favorable in vitro and in vivo characteristics of curcumin

The goal of this study was to assess the enhanced elementary characteristics, in vitro release, anti-cancer cytotoxicity, in situ absorption and in vivo bioavailability of a novel nanoemulsion based lipid nanosystems containing curcumin (CNELNs) when administered orally. The CNELNs were first fabricated by loading water-in-oil nanoemulsions into lipid nanosystems using a nanoemulsion-film dispersion-sonication method. The gastro-intestinal absorption, in vitro release and in vivo kinetic property of CNELNs were investigated using an in situ perfusion method, a dialysis method and a concentration-time curve based method, respectively. The inhibitory effects of CNELNs on human lung cancer A549 cell growth were determined using MTT assay. The absorption constants and effective permeabilities of CNELNs in different gastro-intestinal tracts increased 2.29-4.04 times and 4.06-8.27 times that of curcumin (CUR), respectively. The relative bioavailability of CNELNs to free CUR was 733.59%. CNELNs inhibited A549 growth in a dose- and time-dependent manner. CNELNs markedly improved the oral bioavailability of CUR which was probably due to the increased gastro-intestinal absorption. CNELNs had stronger inhibitory effects on the viabilities of A549 cells than that of free CUR. CNELNs might be promising nanosystems for oral delivery of CUR to satisfy clinical requirements.

Release of outer membrane vesicles in Pseudomonas putida as a response to stress caused by cationic surfactants

Pseudomonas putida A (ATCC 12633), a degrader of cationic surfactants, releases outer membrane vesicles (OMVs) when grown with tetradecyltrimethylammonium bromide (TTAB) as the sole carbon, nitrogen and energy source. The OMVs exhibit a bilayer structure and were found to be composed of lipopolysaccharides, proteins and phospholipids (PLs) such as cardiolipin, phosphatidylcholine, phosphatidic acid and phosphatidylglycerol (PG). The OMVs showed a marked increase in the PG content, approximately 43 % higher than the amount registered in the parent cells from which the vesicles were derived. After growth of P. putida with TTAB, the amount of lipoprotein covalently cross-linked to the peptidoglycan showed a twofold decrease when compared with values found after growth without the surfactant [16 ± 2 and 28 ± 3 μg (mg cell envelope protein)- 1, respectively]. This decrease in the amount of lipoprotein can be related to areas of loss of contact between the outer membrane and the peptidoglycan and, therefore, to OMV production. In addition, due to its amphiphilic nature, TTAB can contribute to OMV biogenesis, through a physical mechanism, by induction of the curvature of the membrane. Taking into account that OVMs were produced when the cells were grown under external stress, caused by the surfactant, and that TTAB was detected in the vesicles [48 nmol TTAB (nmol PL)- 1], we concluded that this system of TTAB elimination is a mechanism that P. putida A (ATCC 12633) would utilize for alleviating stress caused by cationic surfactants.

Functional nanoemulsion-hybrid lipid nanocarriers enhance the bioavailability and anti-cancer activity of lipophilic diferuloylmethane

The purpose of this study was to assess the enhanced physicochemical characteristics, in vitro release behavior, anti-lung cancer activity, gastrointestinal absorption, in vivo bioavailability and bioequivalence of functional nanoemulsion-hybrid lipid nanocarriers containing diferuloylmethane (DNHLNs). The DNHLNs were first fabricated by loading water-in-oil nanoemulsions into hybrid lipid nanosystems using nanoemulsion-thin film-sonication dispersion technologies. The in situ absorption and in vitro and in vivo kinetic features of DNHLNs were measured using an in situ unidirectional perfusion method, a dynamic dialysis method and a plasma concentration-time profile-based method, respectively. The cytotoxic effects of DNHLNs in lung adenocarcinoma A549 cells were examined using MTT colorimetric analysis. The absorptive constants and permeabilities of DNHLNs in four gastrointestinal sections increased by 1.43-3.23 times and by 3.10-7.76 times that of diferuloylmethane (DIF), respectively. The relative bioavailability of DNHLNs to free DIF was 855.02%. DNHLNs inhibited cancer cell growth in a time- and dose-dependent manner. DNHLNs markedly improved the absorption and bioavailability of DIF after oral administration. DNHLNs had stronger inhibitory effects on the viability of A549 cells than that of free DIF. DNHLNs might be potentially promising nanocarriers for DIF delivery via the oral route to address unmet clinical needs.