Browsing by Subject "CELL-WALL"

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  • Liu, Miao; Liu, Xingxing; Kang, Jieyu; Korpelainen, Helena; Li, Chunyang (2020)
    This study clarifies the mechanisms of Cd uptake, translocation and detoxification in Populus cathayana Rehder females and males, and reveals a novel strategy for dioecious plants to cope with Cd contamination. Females exhibited a high degree of Cd uptake and root-to-shoot translocation, while males showed extensive Cd accumulation in roots, elevated antioxidative capacity, and effective cellular and bark Cd sequestration. Our study also found that Cd is largely located in epidermal and cortical tissues of male roots and leaves, while in females, more Cd was present in vascular tissues of roots and leaves, as well as in leaf mesophyll. In addition, the distributions of sulphur (S) and phosphorus (P) were very similar as that of Cd in males, but the associations were weak in females. Scanning electron microscopy and energy spectroscopy analyses suggested that the amounts of tissue Cd were positively correlated with P and S amounts in males, but not in females (a weak correlation between S and Cd). Transcriptional data suggested that Cd stress promoted the upregulation of genes related to Cd uptake and translocation in females, and that of genes related to cell wall biosynthesis, metal tolerance and secondary metabolism in males. Our results indicated that coordinated physiological, microstructural and transcriptional responses to Cd stress endowed superior Cd tolerance in males compared with females, and provided new insights into mechanisms underlying sexually differential responses to Cd stress.
  • Lovikka, Ville A.; Rautkari, Lauri; Maloney, Thaddeus C. (2018)
    Details on how cellulosic surfaces change under changing moisture are incomplete and even existing results are occasionally neglected. Unlike sometimes reported, water adsorption is unsuitable for surface area measurements. However, water can be utilized for assessing surface dynamics. Hygroscopic changes of pulp and bacterial cellulose were studied by dehydrating the samples in a low polarity solvent and then introducing them into a moist atmosphere in a dynamic vapor sorption (DVS) apparatus at 0-93% relative humidity (RH). The DVS treatment caused hygroscopicity loss near applied RH maxima, however, the hygroscopicity increased at RH values > 10-20% units lower. Additionally, the hygroscopic changes were partially reversible near the RH maximum. Therefore the hygroscopicity of cellulose could be controlled by tailoring the exposure history of the sample. Hornification reduced these changes. The observations support reported molecular simulations where cellulose was shown to restructure its surface depending on the polarity of its environment.
  • Douillard, Francois P.; Kant, Ravi; Ritari, Jarmo; Paulin, Lars; Palva, Airi; de Vos, Willem M. (2013)
  • Raulinaitis, Vytas; Tossavainen, Helena; Aitio, Olli; Juuti, Jarmo T.; Hiramatsu, Keiichi; Kontinen, Vesa; Permi, Perttu (2017)
    We introduce LytU, a short member of the lysostaphin family of zinc-dependent pentaglycine endopeptidases. It is a potential antimicrobial agent for S. aureus infections and its gene transcription is highly upregulated upon antibiotic treatments along with other genes involved in cell wall synthesis. We found this enzyme to be responsible for the opening of the cell wall peptidoglycan layer during cell divisions in S. aureus. LytU is anchored in the plasma membrane with the active part residing in the periplasmic space. It has a unique Ile/Lys insertion at position 151 that resides in the catalytic site-neighbouring loop and is vital for the enzymatic activity but not affecting the overall structure common to the lysostaphin family. Purified LytU lyses S. aureus cells and cleaves pentaglycine, a reaction conveniently monitored by NMR spectroscopy. Substituting the cofactor zinc ion with a copper or cobalt ion remarkably increases the rate of pentaglycine cleavage. NMR and isothermal titration calorimetry further reveal that, uniquely for its family, LytU is able to bind a second zinc ion which is coordinated by catalytic histidines and is therefore inhibitory. The pH-dependence and high affinity of binding carry further physiological implications.
  • Özel, B; Simsek, Ömer; Akcelik, M; Saris, Per Erik Joakim (2018)
    Nisin is a bacteriocin produced by Lactococcus lactis that has been approved by the Food Drug Administration for utilization as a GRAS status food additive. Nisin can inhibit spore germination and demonstrates antimicrobial activity against Listeria, Clostridium, Staphylococcus, and Bacillus species. Under some circumstances, it plays an immune modulator role and has a selective cytotoxic effect against cancer cells, although it is notable that the high production cost of nisin-a result of the low nisin production yield of producer strains-is an important factor restricting intensive use. In recent years, production of nisin has been significantly improved through genetic modifications to nisin producer strains and through innovative applications in the fermentation process. Recently, 15,400 IU ml-1 nisin production has been achieved in L. lactis cells following genetic modifications by eliminating the factors that negatively affect nisin biosynthesis or by increasing the cell density of the producing strains in the fermentation medium. In this review, innovative approaches related to cell and fermentation systems aimed at increasing nisin production are discussed and interpreted, with a view to increasing industrial nisin production.
  • Mansikkala, Tuomas; Patanen, Minna; Karkonen, Anna; Korpinen, Risto; Pranovich, Andrey; Ohigashi, Takuji; Swaraj, Sufal; Seitsonen, Jani; Ruokolainen, Janne; Huttula, Marko; Saranpaa, Pekka; Piispanen, Riikka (2020)
    Lignans are bioactive compounds that are especially abundant in the Norway spruce (Picea abiesL. Karst.) knotwood. By combining a variety of chromatographic, spectroscopic and imaging techniques, we were able to quantify, qualify and localise the easily extractable lignans in the xylem tissue. The knotwood samples contained 15 different lignans according to the gas chromatography-mass spectrometry analysis. They comprised 16% of the knotwood dry weight and 82% of the acetone extract. The main lignans were found to be hydroxymatairesinols HMR1 and HMR2. Cryosectioned and resin-embedded ultrathin sections of the knotwood were analysed with scanning transmission X-ray microscopy (STXM). Cryosectioning was found to retain only lignan residues inside the cell lumina. In the resin-embedded samples, lignan was interpreted to be unevenly distributed inside the cell lumina, and partially confined in deposits which were either readily present in the lumina or formed when OsO(4)used in staining reacted with the lignans. Furthermore, the multi-technique characterisation enabled us to obtain information on the chemical composition of the structural components of knotwood. A simple spectral analysis of the STXM data gave consistent results with the gas chromatographic methods about the relative amounts of cell wall components (lignin and polysaccharides). The STXM analysis also indicated that a torus of a bordered pit contained aromatic compounds, possibly lignin.
  • Liu, Miao; Bi, Jingwen; Liu, Xiucheng; Kang, Jieyu; Korpelainen, Helena; Niinemets, Ulo; Li, Chunyang (2020)
    Although increasing attention has been paid to the relationships between heavy metal and nitrogen (N) availability, the mechanism underlying adaptation to cadmium (Cd) stress in dioecious plants has been largely overlooked. This study examined Cd accumulation, translocation and allocation among tissues and cellular compartments in Populus cathayana Rehder females and males. Both leaf Cd accumulation and root-to-shoot Cd translocation were significantly greater in females than in males under a normal N supply, but they were reduced in females and enhanced in males under N deficiency. The genes related to Cd uptake and translocation, HMA2, YSL2 and ZIP2, were strongly induced by Cd stress in female roots and in males under a normal N supply. Cadmium largely accumulated in the leaf blades of females and in the leaf veins of males under a normal N supply, while the contrary was true under N deficiency. Furthermore, Cd was mainly distributed in the leaf epidermis and spongy tissues of males, and in the leaf palisade tissues of females. Nitrogen deficiency increased Cd allocation to the spongy tissues of female leaves and to the palisade tissues of males. In roots, Cd was preferentially distributed to the epidermis and cortices in both sexes, and also to the vascular tissues of females under a normal N supply but not under N deficiency. These results suggested that males possess better Cd tolerance compared with females, even under N deficiency, which is associated with their reduced root-to-shoot Cd translocation, specific Cd distribution in organic and/or cellular compartments, and enhanced antioxidation and ion homeostasis. Our study also provides new insights into engineering woody plants for phytoremediation.
  • Tytgat, Hanne L. P.; Rasinkangas, Pia; Ritari, Jarmo; Reunanen, Justus; Aalvink, Steven; Lin, Chia-wei; Palva, Airi; Douillard, Francois P.; de Vos, Willem M. (2021)
    Many studies have established the functional properties of Lacticaseibacillus rhamnosus GG, previously known as Lactobacillus rhamnosus GG, marketed worldwide as a probiotic. The extraordinary capacity of L. rhamnosus GG to bind to human mucus and influence the immune system especially stand out. Earlier, we have shown the key role of its SpaCBA sortase-dependent pili encoded by the spaCBA-srtC1 gene cluster herein. These heterotrimeric pili consist of a shaft pilin SpaA, a basal pilin SpaB, and tip pilin SpaC that contains a mucus-binding domain. Here, we set out to characterize a food-grade non-GMO mutant of L. rhamnosus GG, strain PA11, which secretes its pilins, rather than coupling them to the cell surface, due to a defect in the housekeeping sortase A. The sortase-negative strain PA11 was extensively characterized using functional genomics and biochemical approaches and found to secrete the SpaCBA pili into the supernatant. Given the functional importance and uniqueness of the mucus-binding pili of L. rhamnosus GG, strain PA11 offers novel opportunities towards the characterization and further therapeutic application of SpaCBA pili and their low-cost, large-scale production.
  • Wambui, Joseph; Eshwar, Athmanya K.; Aalto-Araneda, Mariella; Pöntinen, Anna; Stevens, Marc J. A.; Njage, Patrick M. K.; Tasara, Taurai (2020)
    Nisin is a commonly used bacteriocin for controlling spoilage and pathogenic bacteria in food products. Strains possessing high natural nisin resistance that reduce or increase the potency of this bacteriocin against Listeria monocytogenes have been described. Our study sought to gather more insights into nisin resistance mechanisms in natural L. monocytogenes populations by examining a collection of 356 field strains that were isolated from different foods, food production environments, animals and human infections. A growth curve analysis-based approach was used to access nisin inhibition levels and assign the L. monocytogenes strains into three nisin response phenotypic categories; resistant (66%), intermediate (26%), and sensitive (8%). Using this categorization isolation source, serotype, genetic lineage, clonal complex (CC) and strain-dependent natural variation in nisin phenotypic resistance among L. monocytogenes field strains was revealed. Whole genome sequence analysis and comparison of high nisin resistant and sensitive strains led to the identification of new naturally occurring mutations in nisin response genes associated with increased nisin resistance and sensitivity in this bacterium. Increased nisin resistance was detected in strains harboring RsbUG77S and PBPB3V240F amino acid substitution mutations, which also showed increased detergent stress resistance as well as increased virulence in a zebra fish infection model. On the other hand, increased natural nisin sensitivity was detected among strains with mutations in sigB, vir, and dlt operons that also showed increased lysozyme sensitivity and lower virulence. Overall, our study identified naturally selected mutations involving pbpB3 (lm0441) as well as sigB, vir, and dlt operon genes that are associated with intrinsic nisin resistance in L. monocytogenes field strains recovered from various food and human associated sources. Finally, we show that combining growth parameter-based phenotypic analysis and genome sequencing is an effective approach that can be useful for the identification of novel nisin response associated genetic variants among L. monocytogenes field strains.
  • Rytioja, Johanna; Hilden, Kristiina; Di Falco, Marcos; Zhou, Miaomiao; Aguilar-Pontes, Maria Victoria; Sietiö, Outi-Maaria; Tsang, Adrian; de Vries, Ronald; Mäkelä, Miia R. (2017)
    The ability to obtain carbon and energy is a major requirement to exist in any environment. For several ascomycete fungi, (post-)genomic analyses have shown that species that occupy a large variety of habitats possess a diverse enzymatic machinery, while species with a specific habitat have a more focused enzyme repertoire that is well-adapted to the prevailing substrate. White-rot basidiomycete fungi also live in a specific habitat, as they are found exclusively in wood. In this study, we evaluated how well the enzymatic machinery of the white-rot fungus Dichomitus squalens is tailored to degrade its natural wood substrate. The transcriptome and exoproteome of D. squalens were analyzed after cultivation on two natural substrates, aspen and spruce wood, and two non-woody substrates, wheat bran and cotton seed hulls. D. squalens produced ligninolytic enzymes mainly at the early time point of the wood cultures, indicating the need to degrade lignin to get access to wood polysaccharides. Surprisingly, the response of the fungus to the non-woody polysaccharides was nearly as good a match to the substrate composition as observed for the wood polysaccharides. This indicates that D. squalens has preserved its ability to efficiently degrade plant biomass types not present in its natural habitat.