Fluorescence and Infrared Spectrometric Study of Cell Walls from Candida, Kluyveromyces, Rhodotorula and Schizosaccharomyces Yeasts in Relation with Their Chemical Composition

Bone marrow mesenchymal stem cells offer an immune-privileged niche to Cutibacterium acnes in case of implant-associated osteomyelitis

Considered as some of the most devastating complications, Cutibacterium acnes (C. acnes)-related osteomyelitis are among the hardest infections to diagnose and treat. Mesenchymal stem cells (MSCs) secrete number of immunomodulatory and antimicrobial soluble factors, making them an attractive treatment for bacterial infection. In this study, we examined MSCs/C. acnes interaction and analyzed the subsequent MSCs and bacteria's behaviors. Human bone marrow-derived MSCs were infected by C. acnes clinical strain harvested from non-infected bone site. Following 3 h of interaction, around 4% of bacteria were found in the intracellular compartment. Infected MSCs increased the secretion of prostaglandin E2 and indolamine 2,3 dioxygenase immunomodulatory mediators. Viable intracellular bacteria analyzed by infrared spectroscopy and atomic force microscopy revealed deep modifications in the wall features. In comparison with unchallenged bacteria, the viable intracellular bacteria showed (i) an increase in biofilm formation on orthopaedical-based materials, (ii) an increase in the invasiveness of osteoblasts and (iii) persistence in macrophage, suggesting the acquisition of virulence factors. Overall, these results showed a direct impact of C. acnes on bone marrow-derived MSCs, suggesting that blocking the C. acnes/MSCs interactions may represent an important new approach to manage chronic osteomyelitis infections. STATEMENT OF SIGNIFICANCE: The interaction of bone commensal C. acnes with bone marrow mesenchymal stem cells induces modifications in C. acnes wall characteristics. These bacteria increased (i) the biofilm formation on orthopaedical-based materials, (ii) the invasiveness of bone forming cells and (iii) the resistance to macrophage clearance through the modification of the wall nano-features and/or the increase in catalase production.

Transcriptome analysis of Cryptococcus humicola under aluminum stress revealed the potential role of the cell wall in aluminum tolerance

Aluminum (Al) toxicity is one of the most important limiting factors for crop yield in acidic soils. Bound Al gets converted into a toxic ionic state (Al3+) in acidic soil. Recent studies have shown that Al can act on the cell walls, cell membranes, organelles, and nuclei of microorganisms and affect substance and energy metabolism. To explore the gene expression at the transcriptional level under Al stress, we sequenced the transcriptome of Cryptococcus humicola, which is a highly Al-resistant yeast strain isolated from acidic soil and tolerates up to 200 mM Al3+. The screening conditions for genes from the control and experimental group were a false discovery rate (FDR) <0.05 and log 2|FC| > 1. A total of 4760 genes were differentially expressed, among which 3066 were upregulated and 1694 were downregulated. These genes control glycometabolism, protein synthesis, lipid metabolism and signalling pathways. Eleven selected differentially expressed genes were further validated using qRT-PCR. The results suggested that Al stress leads to complex responses in C. humicola. The effects of Al on the β-d-glucan and mannose contents and Al accumulation in the cell wall were determined. With an increase in the Al treatment time and concentration, the contents of β-d-glucan and mannose showed a trend of first increasing and then decreasing. Under Al treatment, the Al content of the cell wall also showed a trend of first increasing and then decreasing. These results suggested that Al accumulates in the cell wall and the cell wall plays a vital role in the Al resistance of C. humicola. The differentially expressed genes provide a foundation for the further study of Al tolerance in C. humicola.

Early fungi from the Proterozoic era in Arctic Canada

Fungi are crucial components of modern ecosystems. They may have had an important role in the colonization of land by eukaryotes, and in the appearance and success of land plants and metazoans^1-3. Nevertheless, fossils that can unambiguously be identified as fungi are absent from the fossil record until the middle of the Palaeozoic era^4,5. Here we show, using morphological, ultrastructural and spectroscopic analyses, that multicellular organic-walled microfossils preserved in shale of the Grassy Bay Formation (Shaler Supergroup, Arctic Canada), which dates to approximately 1,010-890 million years ago, have a fungal affinity. These microfossils are more than half a billion years older than previously reported unambiguous occurrences of fungi, a date which is consistent with data from molecular clocks for the emergence of this clade^6,7. In extending the fossil record of the fungi, this finding also pushes back the minimum date for the appearance of eukaryotic crown group Opisthokonta, which comprises metazoans, fungi and their protist relatives^8,9.

A potential contribution of the less negatively charged cell wall to the high aluminum tolerance of Rhodotorula taiwanensis RS1

Rhodotorula taiwanensis RS1 (Rt) is a high-aluminum (Al)-tolerant yeast that can survive Al at concentrations up to 200 mM. In this study, we compared Rt with an Al-sensitive congeneric strain, R. mucilaginosa AKU 4812 (Rm) and Al sensitive mutant 1 (alsm1) of Rt, to explore the Al tolerance mechanisms of Rt. The growth of Rm was completely inhibited by 1 mM Al, but that of Rt was not inhibited until Al concentration was more than 70 mM. The growth of alsm1 was inhibited much more by 70 mM and 100 mM Al than that of Rt. Compared with Rm cells, Rt cells accumulated less Al in the cell wall and cytoplasm. A time-course analysis showed that Al was absorbed by Rm cells much more rapidly than by Rt cells when exposed to the same Al concentration. Meanwhile, the Al content of alsm1 was higher than that of Rt. Although the cell wall of Rt was thicker than that of alsm1 and Rm under control and 0.1 mM Al, that of Rt was thinner than that of alsm1 under 70 mM Al despite that their cell walls were thickened. The alcian blue adsorption was lower and cell wall zeta-potential was higher in Rt and alsm1 than in Rm, indicating a less negative charge of cell wall of Rt and alsm1 than that of Rm. Taken together, the less negatively charged cell wall of Rt may restrict the adsorption of cationic Al in cells, potentially contributing to its high Al tolerance. Copyright © 2016 John Wiley & Sons, Ltd.

Uranium Binding Mechanisms of the Acid-Tolerant Fungus Coniochaeta fodinicola

The uptake and binding of uranium [as (UO2)(2+)] by a moderately acidophilic fungus, Coniochaeta fodinicola, recently isolated from a uranium mine site, is examined in this work in order to better understand the potential impact of organisms such as this on uranium sequestration in hydrometallurgical systems. Our results show that the viability of the fungal biomass is critical to their capacity to remove uranium from solution. Indeed, live biomass (viable cells based on vital staining) were capable of removing ∼16 mg U/g dry weight in contrast with dead biomass (autoclaved) which removed ∼45 mg U/g dry weight after 2 h. Furthermore, the uranium binds with different strength, with a fraction ranging from ∼20-50% being easily leached from the exposed biomass by a 10 min acid wash. Results from X-ray absorption spectroscopy measurements show that the strength of uranium binding is strongly influenced by cell viability, with live cells showing a more well-ordered uranium bonding environment, while the distance to carbon or phosphorus second neighbors is similar in all samples. When coupled with time-resolved laser fluorescence and Fourier transformed infrared measurements, the importance of organic acids, phosphates, and polysaccharides, likely released with fungal cell death, appear to be the primary determinants of uranium binding in this system. These results provide an important progression to our understanding with regard to uranium sequestration in hydrometallurgical applications with implications to the unwanted retention of uranium in biofilms and/or its mobility in a remediation context.

Distinction of fungal polysaccharides by N/C ratio and mid infrared spectroscopy

A set of fungal polysaccharide samples was characterised by elemental analysis and FTIR spectroscopy and compared with reference chitins, chitosans and β-D-glucans. The nitrogen to carbon (N/C) values and FTIR spectra were used to compare the samples based on their composition. It was found that the N/C ratio correlates well with deacetylation degree (DD) of chitosans and chitin/glucan ratio R(chit) of fungal chitin – β-D-glucan complexes with the exception of some samples having significant nitrogen and/or carbon admixtures. FTIR spectroscopy was indicative for the N-acetylation of chitins (chitosans) as well as for the chitin (chitosan) contribution to fungal polysaccharide preparations. Multivariate analyses of the FTIR data (HCA, PCA) discriminated samples and reference materials into several clusters depending on their similarity. Chitosan lactates, chitosan – β-D-glucans and chitin – β-D-glucans of high and low amounts of chitin were successfully discriminated from the reference polysaccharides and from each other. The proposed procedures based on the N/C ratio and multivariate analyses of FTIR spectra may be used in screening fungal polysaccharide preparations.

On the production of glycogen by Pseudomonas fluorescens during biofilm development: an in situ study by attenuated total reflection-infrared with chemometrics

Attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy was used to monitor Pseudomonas fluorescens biofilms in situ, non-destructively, in real time, and under fully hydrated conditions. Changes accompanying the metabolic evolution of the sessile bacterial cells from the nascent biofilm monolayer to the beginning of the multi-layered structure in the presence of nutrients were identified via the ATR-FTIR fingerprints of the young biofilm on the ATR crystal. The ATR-FTIR spectra were analysed by classical methods (time evolution of integrated intensities and profile evolution of specific bands), and also by a multivariate curve resolution, Bayesian positive source separation, to extract the pure component spectra and their change of concentration over time occurring during biofilm settlement. This work showed clearly the overproduction of glycogen by sessile P. fluorescens, which had not previously been described by other research groups.

Li+ effect on the cell wall of the yeast Saccharomyces cerevisiae as probed by FT-IR spectroscopy

The effect of Li+ ions as a transformation inducing agent on the yeast cell wall has been studied. Two Saccharomyces cerevisiae strains, p63-DC5 with a native cell wall, and strain XCY42-30D(mnn1) which contains structural changes in the mannan-protein complex, were used. Fourier transform infrared (FT-IR) spectroscopy has been used for the characterization of the yeast strains and for determination of the effect of lithium cations on the cell wall. A comparison of the carbohydrate absorption band positions in the 970–1185 cm−1 range, of Na+ and Li+ treated yeast cells has been estimated. Absorption band positions of the cell wall carbohydrates of p63-DC5 were not influenced by the studied ions. On the contrary, the treatment of XCY42-30D(mnn1) cells with Li+ ions shifted glucan band positions, implying that the cell wall structure of strain XCY42-30D(mnn1) is more sensitive to Li+ ion treatment.

Stabilization of astaxanthin by a novel biosurfactant produced by Rhodotorula mucilaginosa KUGPP-1

We found that a novel biosurfactant from the cultured broth of red yeast, Rhodotorula mucilaginosa KUGPP-1, originating in the Antarctic, has dispersive power against astaxanthin. The novel biosurfactant was purified from extracts to the ultrafiltration state by acetone precipitation and chromatography on a DEAE-Toyopearl 650 M, and gel filtration on a Sephacryl S-400 HR. The molecular mass of the novel biosurfactant was estimated to be about 730,000 by gel filtration chromatography. The novel biosurfactant was comprised of sugar and protein in an approximate molar ratio of 9 : 1. The sugars were comprised of mannose, galactose and glucose. The particle size of the astaxanthin (0.13 µ g/ml) micelle was about 410 nm. Astaxanthin was stable to oxidation in the novel biosurfactant micelles. To our knowledge, this is the first report on a glycoprotein type of biosurfactant with astaxanthin-stabilizing ability.

Production of extracellular glycogen by Pseudomonas fluorescens: spectroscopic evidence and conformational analysis by biomolecular recognition

Glycogen is mainly found as the principal storage form of glucose in cells. Many bacteria are able to synthesize large amounts of glycogen under unfavorable life conditions. By combining infrared spectroscopy, single molecule force spectroscopy (SMFS) and immuno-staining technique, we evidenced that planktonic P. fluorescens (Pf) cells are also able to produce glycogen as an extracellular polymeric substance. For this purpose, Pf suspensions were examined at 3 and 21 h of growth in nutritive medium (LB, 0.5 g/L). The conformation of the extracellular glycogen, revealed through its infrared spectral signature, has been investigated by SMFS measurements using Freely Jointed Chain model. The analysis of force versus distance curves showed over growth time that the increase of glycogen production was accompanied by an increase in glycogen contour lengths and ramifications. These results demonstrated that the production of extracellular bacterial glycogen can occur even if the cells are not subjected to unfavorable life conditions.

Is there anyone out there?--Single-molecule atomic force microscopy meets yeast genetics to study sensor functions

The ability to react to environmental stress is a key feature of microbial cells, which frequently involves the fortification of their cell wall as a primary step. In the model yeast Saccharomyces cerevisiae the biosynthesis of the cell wall is regulated by the so-called cell wall integrity signal transduction pathway, which starts with the detection of cell surface stress by a small family of five membrane-spanning sensors (Wsc1-Wsc3, Mid2, Mtl1). Although genetic evidence indicated that these proteins act as mechanosensors, direct in vivo evidence for their function remained scarce. Here, we review a new approach integrating the tools and concepts of genetics with those of nanotechnology. We show how atomic force microscopy can be combined with advanced protein design by yeast genetics, to study the function and the mechanical properties of yeast sensors in living cells down to the single molecule level. We anticipate that this novel integrated technology will enable a paradigm shift in cell biology, so that pertinent questions can be addressed, such as the nanomechanics of single sensors and receptors, and how they distribute across the cell surface when they respond to extracellular stress.

A synchrotron FTIR microspectroscopy investigation of fungal hyphae grown under optimal and stressed conditions

Synchrotron FTIR can provide high spatial resolution (<10 microm pixel size) in situ biochemical analyses of intact biotissues, an area of increasing importance in the post-genomic era, as gene functions and gene networks are coming under direct scrutiny. With this technique, we can simultaneously assess multiple aspects of cell biochemistry and cytoplasmic composition. In this paper, we report the first results of our synchrotron FTIR examination of hyphae of three important fungal model systems, each with sequenced genomes and a wealth of research: Aspergillus, Neurospora, and Rhizopus. We have analyzed the FTIR maps of Aspergillus nidulans cells containing the hypA1 allele, a well-characterized single-gene temperature-sensitive morphogenetic mutation. The hypA1 cells resemble wildtype at 28 degrees C but have growth defects at 42 degrees C. We have also investigated Neurospora and Rhizopus cultures grown in media with optimal or elevated pH. Significant differences between the spectra of the three fungi are likely related to differences in composition and structure. In addition, high spatial resolution synchrotron FTIR spectroscopy provides an outstanding method for monitoring subtle subcellular changes that accompany environmental stress.