Ag Nanorod Arrays for SERS: Aspects of Spectral Reproducibility, Surface Contamination, and Spectral Sensitivity

Ag nanorod arrays prepared by oblique angle vapor deposition (OAD) represent regular, large area substrates for surface-enhanced Raman scattering (SERS) spectroscopy. We studied uniformity and spectral reproducibility of silver OAD-fabricated substrates (AgOADs) by spectral mapping of methylene blue. The results demonstrate good reproducibility apart from occasional “hot-spot” sites where the intensity is higher. The number of “hot-spots” represents 2%–6% of SERS-active sites of mapping substrate area. We were able to obtain good SERS spectra of testing amino acid tryptophan at 1 × 10−5 M concentration and three different free-base porphyrins down to ∼10−7 M concentration. We found out that keeping the AgOADs in a vacuum chamber overnight prevents the surface from binding any contaminants from the ambient atmosphere, without significant reduction in the SERS enhancement. Such substrates provide stable SERS enhancement even when stored for 1 year after preparation

Studium fotobiontů lichenizovaného rodu Lepraria

My study is focused on green algal photobionts - lichenized algae from the genera Asterochloris and Trebouxia (the last was studied in a lesser extent). The principal objectives of the thesis can be characterized as follows: 1) to investigate the chloroplast morphology in lichenized algae Asterochloris and Trebouxia; 2) to study the photobiont diversity in lichen community growing in heavy metal polluted habitats; 3) to inventorize the photobionts in selected lichen taxa (Lepraria, Stereocaulon) in order to reveal their ecological requirements. Using confocal microscopy, significant differences in the chloroplast structure of lichenized and cultured (free-living) algae were detected. Moreover, algae exhibited gradual changes in chloroplast shape and structure during successive phases of cultivation - from the relatively simple lichenized form to the complex lobate chloroplast with several ontogenetic (morphological) stages observable in mature axenic cultures. Several Asterochloris lineages and one Trebouxia species were detected in terricolous lichen community from metal-polluted habitats using phylogenetic analysis of algal ITS sequences. All these lineages represented photobionts with broad ecological amplitude and worldwide distribution. In several taxa of pioneer lichens, low specificity as..

Lichens-a new source or yet unknown host of herbaceous plant viruses?

Abstract Lichens are symbiotic associations of fungi with green algae or cyanobacteria. They have arisen independently several times within the Ascomycota and Basidiomycota. This symbiosis became with time one of the most successful life forms on Earth. Outside of the symbiotic algae and fungi, there are endophytic fungi, other algae, and lichen-associated bacteria present within lichen thalli. Till now, no lichen-specific pathogens have been reported among bacteria and viruses. Around 15 dsRNA viruses are known from Eurotiomycetes and another dsRNA and reverse transcribed ssRNA viruses from Dothideomycetes containing some lichenized fungal lineages. Algal viruses have been identified from less than 1 % of known eukaryotic algal species but no virus has been found in Trebouxia or in Trentepohlia (Chlorophyta, Pleurastrophyceae, Pleurastrales), the most common green lichen photobionts. On the other hand, dsDNA viruses infecting related Chlorella algae are well known from freshwater phytoplankton. However, high-molecular weight dsRNA isolated from different lichen thalli indicated to us presence of ss or dsRNA viruses. A PCRbased search for viruses with genus-specific and speciesspecific primers resulted in amplification of genome segments highly identical with those of plant cytorhabdoviruses and with Apple mosaic virus (ApMV). The nucleotide sequence of the putative lichen cytorhabdovirus showed high identity (98 %) with Ivy latent cytorhabdovirus. The nucleotide sequences of six Apple mosaic virus isolates from lichens showed high similarity with ApMV isolates from apple and pear hosts. The lichen ApMV isolates were mechanically transmitted to an herbaceous host and detected positive in ELISA 14 days thereafter, which support its infectivity on plants. We prepared axenic cultures of photobionts identified as Trebouxia sp. from this ApMVpositive lichen samples. All these cultures were positive for ApMV in RT-PCR test. We suggest that lichens as a whole (or their photobionts, more specifically) could serve as reservoirs for viruses, despite the fact that the way of transmission between different organisms is not Eur J Plant Patho

Ekologická rozhraní: interakce živého a neživého v povrchových mikroekosystémech půd a antropogenních substrátů

Výsledky za rok jsou uvedeny v kapitolách: A. Abiotické a ekofyziologické charakteristiky studovaných lokalit, B. Studium sinic a řas, C. Studium hub, D. Studium lišejníků, E. Studium mechorostů, F. Inokulace substrátu sinicí rodu Nostoc. Uveden je přehled o čerpání finančních prostředků

Ekologická rozhraní: interakce živého a neživého v povrchových mikroekosystémech půd a antropogenních substrátů

V roce 2005 byl studován soubor dvanácti lokalit - tři přírodní stanoviště, pět odkališť, dvě výsypky a dvě kulturní plochy. Předběžné výsledky jednotlivých pracovních skupin: algologické, mykologické, bryologicko-lichenologické a geobotanické