Candida albicans Tpk1p and Tpk2p isoforms differentially regulate pseudohyphal development, biofilm structure, cell aggregation and adhesins expression

Candida albicans undergoes a reversible morphological transition from single yeast cells to pseudohyphal and hyphal filaments. In this organism, cAMP-dependent protein kinase (PKA), coded by two catalytic subunits (TPK1 and TPK2) and one regulatory subunit (BCY1), mediates basic cellular processes, such as the yeast-to-hypha transition and cell cycle regulation. It is known that both Tpk isoforms play positive roles in vegetative growth and filamentation, although distinct roles have been found in virulence, stress response and glycogen storage. However, little is known regarding the participation of Tpk1p and/or Tpk2p in pseudohyphal development. This point was addressed using several C. albicans PKA mutants having heterozygous or homozygous deletions of TPK1 and/or TPK2 in different BCY1 genetic backgrounds. We observed that under hypha-only inducing conditions, all BCY1 heterozygous strains shifted growth toward pseudohyphal morphology; however, the pseudohypha:hypha ratio was higher in strains devoid of TPK2. Under pseudohypha-only inducing conditions, strains lacking TPK2 were prone to develop short and branched pseudohyphae. In tpk2 Δ/tpk2 Δ strains, biofilm architecture was markedly less dense, composed of short pseudohyphae and blastospores with reduced adhesion ability to abiotic material, suggesting a significant defect in cell adherence. Immunolabelling assays showed a decreased expression of adhesins Als1p and Als3p only in the tpk2 Δ/tpk2 Δ strain. Complementation of this mutant with a wild-type copy of TPK2 restored all the altered functions: pseudohyphae elongation, biofilm composition, cell aggregation and adhesins expression. Our study suggests that the Tpk2p isoform may be part of a mechanism underlying not only polarized pseudohyphal morphogenesis but also cell adherence.     

Shelf life of cashew nut kernels packed in banana starch-based nanocomposites

Starch-based films incorporated with cellulose nanofibres (CNFs) were tested as packaging to improve the stability of cashew nut kernels (CNKs). CNKs were conditioned in four packings: commercial polyethylene film (PEF), starch film (CF), nanocomposite CHF (starch + CNFs from chemical hydrolysis) and nanocomposite EHF (starch + CNFs from enzymatic hydrolysis). Effect of the packaging methods on peroxides value (POV), acidity value (AV), weight gain (WG), water activity (Aw), hardness and colour properties of the CNKs was investigated. CNKs packed with CHF and EHF showed lower POV (0.91 and 0.92 meq_peroxide/kg_sample, respectively) after 21 days of storage than other packed (1.07–1.13 meq_peroxide/kg_sample) and unpacked samples (1.32 meq_peroxide/kg_sample). CNKs packaged with nanocomposites presented similar WG to samples packaged with PEF and lower values than unpackaged CNKs. Biodegradable nanocomposites films showed potential to be used as packaging for food product, being an effective material for extending oilseeds shelf life.     

Nanodelivery of the Gramicidin Peptide for Enhancing Antimicrobial Activity

Gramicidin S (GraS) is an amphiphilic peptide that has emerged as an effective alternative antibiotic. However, its applicability is restricted for clinical uses due to its effect on eukaryotic cells and low aqueous solubility. In this work, a novel water-soluble peptide formulation with bactericidal activity is developed by the incorporation of Gramicidin S in the lipid bilayer of liposomes (L-GraS). As a result, GraS included in the lipid vesicles is stabilized in aqueous medium and showed antimicrobial activity against Staphylococcus aureus. In addition, L-GraS reveals enhanced biocompatibility with mammalian cells in comparison with the free peptide. Molecular dynamics simulations shed light on the collective behavior between GraS peptides and liposomes from a molecular approach. The molecular dynamic simulations are in agreement with experimental results and further confirm the effective incorporation of GraS in the liposomes, letting understand the best formulation procedure of the vesicles. Therefore, the L-GraS nanosystem presented here is an interesting alternative to conventional antibiotics, with less restrictions and promising features to improve current therapies. Practical Applications: Incorporation of GraS in liposomes is an interesting approach to increase the solubility of the peptide, thus expanding its therapeutic horizon as a promising alternative to combat bacterial colonization especially in wound infections.     

Can the maximum volume fraction ensure optimum reinforcement in short-fiber composites?

Short sisal fiber composites (SSFCs) based on a pectin matrix were prepared and characterized mechanical and optically. Different concentrations (1–30 wt %) of fibers were used to evaluate the packing effect on the reinforcement of a polymer matrix. Theoretical models were used to obtain the maximum packing or volume fraction (ϕ_max) of randomly oriented short fibers and its relationship with the mechanical parameters. A higher elastic modulus and tensile strength were observed when the fiber content was increased in the composite at a fixed aspect ratio (length/diameter = 2.8). Material selection charts showed that SSFCs with a fiber concentration of 20 wt % had a higher reinforcement effect at ϕ_max, as was predicted through theoretical models. Nevertheless, SSFCs with a fiber concentration of 7 wt % presented optimum reinforcement because it resulted in the strongest and lightest composite material. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47821.     

Feasibility of a flip-chip approach to integrate an IR filter and an IR detector in a future gas detection cell

In this work we have studied the feasibility of integrating an infrared filter and an infrared detector by means of a flip-chip technique. This filter and detector combination should be the heart of a future gas detection cell based on infrared absorption. In our case the filter is a surface micromachined Fabry-Perot interferometer, and the infrared detector is a bulk micromachined thermopile. The flip-chip technique is an elegant solution to assure the optical micro-alignment of both devices and allows the electrical contact needed to actuate active optical filters.Work originally presented at DTIP 2003. Spanish CICYT projects no TIC-98-0987-C03-03 and DPI-2001-3213-C02-01 have financed this work.     

Effects of conventional and nonconventional drying on the stability of Bifidobacterium animalis subsp. lactis INL1

Freeze, spray, vacuum, microwave vacuum‐ and microwave freeze‐drying were applied to Bifidobacterium animalis subsp. lactis INL1. Freeze and microwave freeze‐drying showed the highest survival after drying. When a storage test (25 °C; oxygen) was performed, these cultures were the most sensitive ones at a_w = 0.23, but the addition of lactose improved their stability after 8 weeks. Flow cytometry was useful to assess viability after drying but not during storage. Our results show that dehydration technologies other than freeze‐drying might be suitable alternatives that deserve further investigation for the preservation of sensitive probiotic bacteria. Microwave drying rendered cultures of comparable characteristics to their conventional counterparts, requiring significantly shorter drying times.