Study of Antibacterial Activity of ZnZnbisporphyrin Complexes and its Free Components on <Emphasis Type="Italic">Staphylococcus aureus</Emphasis> by Microcalorimetry

The antibacterial effect of Zn(II), tetraphenyl porphyrin (TPP), propdioxyl bridged tetraphenyl bisporphyrin 1, and its metallobisporphyrin complexes (ZnMnbisporphyrin 2 and ZnZnbisporphyrin 3) towards Staphylococcus aureus growth was investigated by microcalorimetry at 37°C. Differences in their capacities to inhibit the growth metabolism of S. aureus were observed. By analyzing the power–time curves, crucial parameters such as the rate constant of bacterial growth (k), inhibitory ratio (I), and generation time (t _G) were determined. The growth rate constant (k) of S. aureus (in the log phase) in the presence of the drugs decreased linearly with increasing concentrations of the complexes. The sequence of the antibacterial activities of these compounds tested was 3 > 2 > 1 > Zn(II) > TPP. ZnZnbisporphyrin 3 is proposed to benefit from the synergetic effects of Zn(II) and 1.     

Phytochemical, antimicrobial, antioxidant and antigenotoxic potentials of Cyperus rotundus extracts

The aqueous, ethyl acetate, methanolic and Total Oligomer Flavonoids (TOF) enriched extracts, obtained from the aerial parts of Cyperus rotundus, were investigated for their contents in phenolic compounds. Antioxidative activity using the NBT/riboflavin assay system, antimicrobial activity against Gram positive and Gram negative bacterial reference strains as well as antigenotoxic activity tested with the SOS chromotest assay were also studied. Significant antibacterial activity against reference strains; Staphylococcus aureus, Enterococcus faecalis, Salmonella enteritidis and Salmonella typhimurium, was detected in the presence of ethyl acetate and TOF enriched extracts. In addition to their antimicrobial activity, the same extracts showed a significant ability to inhibit nitroblue tetrazolium reduction by the superoxide radical in a non enzymatic O₂^.− generating system, and were also able to reduce significantly the genotoxicity induced by nifuroxazide and Aflatoxin B1. The antioxidant, antimicrobial and antigenotoxic activities exhibited by C. rotundus depend on the chemical composition of the tested extracts.     

Pigment profiles and bacterial communities from Thailand thermal mats

Differently colored layers of freshwater hot spring mats at Boekleung (Western Thailand) were studied. Temperatures ranged from over 50 up to 57°C. Two mats were characterized: a laminated mat with a green and a red layers, and a monolayer, greenish-yellow mat. Bacterial communities in green, red, and yellow layers were investigated using molecular, culturing and pigment analysis methods. Pigment profiles covered a wide spectrum from chlorophylls to carotenoids. A green mat layer showed higher relative content of chlorophyll than yellow and red layers which presented higher proportion of carotenoids. Cyanobacterial isolates grow up to 55–56°C and their pigment profiles showed a relatively high content of chlorophylls suggesting the importance of other bacterial groups in the mat pigment profiles. Bacterial communities were analyzed by 16S rDNA surveys showing Cyanobacteria and Chloroflexi as the mayor components of the community. Other significant members were Candidate Division OP10, Bacteroidetes, Planctomycetes and Actinobacteria. These results highlight a major participation of Cyanobacteria and Chloroflexi in thermal mat communities, and the preferential presence of Candidate Division OP10 in green mat layers. Differently colored mat layers showed characteristic bacterial communities which could be discriminated from pigment profiles and molecular surveys.     

Antifouling Potential of Some Marine Organisms from India Against Species of Bacillus and Pseudomonas

Crude methanolic extracts of 37 marine organisms (16 species of flora, 21 species of fauna) were screened for antibacterial properties against 5 strains of bacteria isolated from marine environments. Of these, 10 plant and 9 animal extracts exhibited antibacterial activity against at least one bacterial strain. The extracts of 6 species were active against all the strains: i.e., Stoechospermum marginatum (brown algae), Cymodocea rotundata (seagrass), Petrosia sp. and Psammaplysilla purpurea (sponges), Sinularia compressa (soft coral), and Cassiopeia sp. (jellyfish). Among the plants, Padina tetrastromatica (brown algae) extract exhibited significant activity (9–11-mm inhibition zone at 500 μg per 6-mm disc) against Bacillus pumilus and Pseudomonas vesicularis, while the extracts of Petrosia, Psammaplysilla, and Cassiopeia were strongly active (11–13-mm inhibition zone at 500 μg per 6-mm disc) against B. circulans and P. putida. It was further confirmed that the attachment of bacterial strains on glass slides was inhibited remarkably with increasing concentrations of bioextracts of Petrosia sp. and Psammaplysilla purpurea. The present findings could form the basis for exploring the antibacterial potential of bioactive molecules from some of the marine organisms that exhibited moderate to strong antibacterial properties.     

Antioxidant and antimicrobial actions of the clubmoss <Emphasis Type="Italic">Lycopodium clavatum</Emphasis> L.

Purpose of the present study was to evaluate antioxidant, antibacterial, antifungal, and antiviral activities of the petroleum ether, chloroform, ethyl acetate and methanol extracts as well as the alkaloid fraction of Lycopodium clavatum L. (LC) from Lycopodiaceae growing in Turkey. Antioxidant activity of the LC extracts was evaluated by 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging method at 0.2 mg/ml using microplate-reader assay. Antiviral assessment of LC extracts was evaluated towards the DNA virus Herpes simplex (HSV) and the RNA virus Parainfluenza (PI-3) using Madin-Darby Bovine Kidney (MDBK) and Vero cell lines. Antibacterial and antifungal activities of the extracts were tested against standard and isolated strains of the following bacteria; Escherichia coli, Pseudomonas aeruginosa, Proteus mirabilis, Acinobacter baumannii, Klebsiella pneumoniae, Staphylococcus aureus, Bacillus subtilis as well as the fungi; Candida albicans and C. parapsilosis. All of the extracts possessed noteworthy activity against ATCC strain of S. aureus (4 μg/ml), while the LC extracts showed reasonable antifungal effect. On the other hand, we found that only the chloroform extract was active against HSV (16–8 μg/ml), while petroleum ether and alkaloid extracts inhibited potently PI-3 (16–4 μg/ml and 32–4 μg/ml, respectively). However, all of the extracts had insignificant antiradical effect on DPPH. In addition, we also analyzed the content of the alkaloid fraction of the plant by capillary gas chromatography-mass spectrometry (GC-MS) and identified lycopodine as the major alkaloid.     

Bacterial diversity from benthic mats of Antarctic lakes as a source of new bioactive metabolites

During the MICROMAT project, the bacterial diversity of microbial mats growing in the benthic environment of Antarctic lakes was accessed for the discovery of novel antibiotics. In all, 723 Antarctic heterotrophic bacteria belonging to novel and/or endemic taxa in the α-, β- and γ-subclasses of the Proteobacteria, the Bacteroidetes branch, and of the high and low percentage G+C Gram-positives, were isolated, cultivated in different media and at different temperatures, and then screened for the production of antimicrobial activities. A total of 6348 extracts were prepared by solid phase extraction of the culture broths or by biomass solvent extraction. 122 bacteria showed antibacterial activity against the Gram-positives Staphylococcus aureus and to a lower extent Enterococcus faecium, and versus the Gram-negative Escherichia coli. Few of these strains showed also some antifungal activity against Cryptococcus neoformans, Aspergillus fumigatus and to a lower extent Candida albicans. LC–MS fractionation of extracts from a subset of strains (hits) that exhibited relatively potent antibacterial activities evidenced a chemical novelty that was further investigated. Two strains of Arthrobacter agilis produced potent antibacterial compounds with activity against Gram-positives and possibly related to novel cyclic thiazolyl peptides. To our knowledge, this is the first report of new antibiotics produced by bacteria from benthic microbial mats from Antarctic lakes. With no doubts these microbial assemblages represent an extremely rich source for the isolation of new strains producing novel bioactive metabolites with the potential to be developed as antibiotic compounds.     

Confocal Laser Scanning Microscopy Image Analysis for Cyanobacterial Biomass Determined at Microscale Level in Different Microbial Mats

We recently published a new method based on determining cyanobacterial biomass by confocal laser scanning microscopy image analysis (CLSM-IA) (Solé et al., Ultramicrosc 107:669–673, 2007). CLSM-IA allows biomass calculation for microorganisms of a small size, since the limit of the technique’s resolution is that generated by a voxel, the smallest unit of a three-dimensional digital image, equivalent to 1.183 × 10⁻³ mgC/cm³ of sediment. This method is especially suitable for the quantitative analysis of a large number of CLSM images generated from benthic sediments in which complex populations of cyanobacteria are abundant, such as microbial mats. In order to validate the new CLSM approach, mats with varying structural characteristics were studied. We have grouped them into three types: Microcoleus mats (laminated), sandy mats (nonlaminated and composed of well-sorted quartz sands), and oil-polluted mats. In this work, we applied CLSM-IA in natural [the Ebro delta and Sant Jordi colony (Spain), Salins-de-Giraud and Etang de Berre (France), and Orkney Islands (Scotland)] and artificial [mesocosms (Israel)] microbial mats. A total of 4,103 confocal images were obtained in order to determine total and individual cyanobacteria biomass profiles, at microscale level. The data presented in this paper show the efficacy of the method, as it can be applied to highly diverse mat samples.     

Diversity of volatile compounds of <Emphasis Type="Italic">afitin</Emphasis>, <Emphasis Type="Italic">iru</Emphasis> and <Emphasis Type="Italic">sonru</Emphasis>, three fermented food condiments from Benin

Volatile compounds in afitin, iru and sonru, three traditional food condiments produced in Benin by natural fermentation of the African locust bean (Parkia biglobosa) were identified and quantified, using the Likens-Nickerson simultaneous distillation-extraction method and GC-MS analysis. A total of 13 chemical groups of volatile compounds were identified and classified in six major groups: pyrazines, aldehydes, ketones, alcohols, esters and benzene derivatives. From these groups, 2,5–dimethylpyrazine, tetramethylpyrazine, 3-methylbutanal, 2-decanone, 3,5-dimethylphenylmethanol, ethyl linoleate and chlorobenzene were found in higher amounts in the three condiments. Afitin was characterized by high concentration of 2-decanone, whereas 2,5-dimethylpyrazine, tetramethylpyrazine, 3-methylbutanal and ethyl linoleate were found particularly in higher concentration, both in iru and sonru.     

Structural and functional properties of sympagic communities in the annual sea ice at Terra Nova Bay (Ross Sea, Antarctica)

Studies on the chemical and biological properties of annual pack ice at a coastal station in Terra Nova Bay (74°41.72′S, 164°11.63′E) were carried out during austral spring at 3-day intervals from 5 November to 1 December 1997. Temporal changes of nutrient concentrations, algal biomasses, taxonomic composition, photosynthetic pigment spectra and P–E relationships were studied. Quantity, composition and degradation rates of organic matter in the intact sea ice were also investigated. In addition, microcosm experiments were carried out to evaluate photosynthetic and photo-acclimation processes of the sympagic flora in relation to different light regimes. High concentrations of ammonia were measured in four ice-cores (weighted mean values of the cores ranged from 4.3 ± 1.9 μM to 7.2 ± 3.4 μM), whereas nitrate and phosphate displayed high concentrations (up to 35.9 μM and 7.6 μM, respectively) only in the bottom layer (135–145 cm depth). Particulate carbohydrate and protein concentrations in the intact sea ice ranged from 0.5 to 2.3 mg l⁻¹ and 0.2 to 2.0 mg l⁻¹, respectively, displaying a notable accumulation of organic matter in the bottom colored layer, where bacterial enzymatic activities also reached the highest values. Aminopeptidase activity was extremely high (up to 19.7 μM l⁻¹ h⁻¹ ± 0.05 in the bottom layer), suggesting a rapid turnover rate of nitrogen–enriched organic compounds (e.g. proteins). By contrast, bacterial secondary production was low, suggesting that only a very small fraction of mobilized organic matter was converted into bacterial biomass (<0.01‰). The sympagic autotrophic biomass (in terms of chlorophaeopigments) of the bottom layer was high, increasing during the sampling period from 680 to 2480 μg l⁻¹. Analyses of pigments performed by HPLC, as well as microscope observations, indicated that diatoms dominated bottom communities. The most important species were Amphiprora sp. and Nitschia cfr. stellata. Bottom sympagic communities showed an average P ^B _max of 0.12 mgC mg Chl⁻¹ and low photoadaptation index (E _k=18 μE m⁻² s⁻¹, E _m=65 μE m⁻² s⁻¹). Results of the microcosm experiment also indicated that communities were photo-oxidized when irradiance exceeded 100 μE m⁻² s⁻¹. This result suggests that micro- autotrophs inhabiting sea ice might have a minor role in the pelagic algal blooms. Accepted: 4 August 1999     

Invasion by a Perennial Herb Increases Decomposition Rate and Alters Nutrient Availability in Warm Temperate Lowland Forest Remnants

We determined the impact of the invasive herb, Tradescantia fluminensis Vell., on litter decomposition and nutrient availability in a remnant of New Zealand lowland podocarp–broadleaf forest. Using litter bags, we found that litter beneath mats of Tradescantia decomposed at almost twice the rate of litter placed outside the mat. Values of k (decomposition quotient) were 9.44±0.42 yrs for litter placed beneath Tradescantia and 5.42±0.42 yrs for litter placed in native, non-Tradescantia plots. The impact of Tradescantia on decomposition was evident through the smaller forest floor mass in Tradescantia plots (2.65±1.05 t ha⁻¹) compared with non-Tradescantia plots (5.05±1.05 t ha⁻¹), despite similar quantities of annual leaf litterfall into Tradescantia plots (6.85±0.85 t ha⁻¹ yr⁻¹) and non-Tradescantia plots (7.45±1.05 t ha⁻¹ yr⁻¹). Moreover, there was increased plant nitrate available, as captured on resin bags, in Tradescantia plots (25.77 ± 8.32 cmol(−)/kg resin) compared with non-Tradescantia plots (9.55±3.72 cmol(−)/kg resin). Finally, the annual nutrient uptake by Tradescantia represented a large proportion of nutrients in litterfall (41% N, 61% P, 23% Ca, 46% Mg and 83% K), exceeded the nutrient content of the forest floor (except Ca), but was a small proportion of the topsoil nutrient pools. Taken together, our results show that Tradescantia increases litter decomposition and alters nutrient availability, effects that could influence the long-term viability of the majority of podocarp–broadleaf forest remnants affected with Tradescantia in New Zealand. These impacts are likely mostly due to Tradescantia's vegetation structure (i.e., tall, dense mats) and associated microclimate, compared with native ground covers. This revised version was published online in July 2006 with corrections to the Cover Date.     

Screening of Malaysian indigenous microalgae for antioxidant properties and nutritional value

Fourteen indigenous microalgal samples from Malaysia were isolated, purified and cultured from fresh, brackish and marine waters. The ability of the microalgae to be natural sources of antioxidants was studied by a screening test using three antioxidant chemical assays [ferric thiocyanate (FTC), thiobarbituric acid (TBA) and 1, 1’-diphenyl-2-picrylhydrazyl (DPPH)]. The results showed that six microalgal methanolic crude extracts (Isochrysis galbana, Chaetoceros calcitrans, Scenedesmus quadricauda, Chlorella vulgaris, Nannochloropsis oculata and Tetraselmis tetrathele) were active in inhibiting the lipid peroxidation of linoleic acid. Among all the microalgae, I. galbana and C. calcitrans showed the highest antioxidant activity (>90%) in FTC and TBA assays, indicating that these microalgae might contain active compounds for protection from lipid peroxidation. Nutritional analyses were performed on microalgae with high antioxidant activities (I. galbana and C. calcitrans) in order to investigate their nutritive value. Both microalgae were found to be rich in nutrients. For examples, I. galbana had average percentage composition of protein, carbohydrate, and lipid, as 47.9 ± 2.5; 26.8 ± 0.2; 14.5 ± 1.4%, respectively, while the corresponding values for C. calcitrans were 36.4 ± 1.7; 27.4 ± 3.0; 15.5 ± 0.9%. In addition, they contained high levels of omega-3 polyunsatrated fatty acids (PUFA) (28.0% ± 0.7 in I. galbana and 28.5% ± 1.4 in C. calcitrans), omega-6 PUFA (6.5% ± 1.8 in I. galbana and 23.0% ± 2.5 in C. calcitrans) and a high composition of essential amino acids. This study illustrates that some microalgae such as I. galbana and C. calcitrans have the potential to be used as natural sources of antioxidants with high nutritional value. Presented at the 6th Meeting of the Asian Pacific Society of Applied Phycology, Manila, Philippines.     

Production of flavour compounds by yogurt starter cultures

The present work studied the production of carbonyl compounds and saturated volatile free fatty acids by pure cultures of Streptococcus thermophilus and Lactobacillus bulgaricus, and by starter cultures for Bulgarian yogurt during cultivation and cooling. The mixed cultures formed volatile aromatic compounds more actively than the pure cultures. A guiding factor in the preparation of the starter cultures was the biochemical activity of Lactobacillus bulgaricus in synthesizing the major carbonyl compounds, acetaldehyde, diacetyl and the volatile fatty acids C₂–C₁₀. The activity of the yogurt cultures in synthesizing carbonyl compounds was at its highest during milk coagulation and cooling, up to 7 h. However, maximum concentration was reached by 22–31 h. In the cooled 22–h starter cultures, acetaldehyde predominated (1415.0–1734.2 μg per 100 g) followed by diacetyl (165.0–202.0 μg per 100 g), acetoin (170.0–221.0 μg per 100 g), acetone (66.0–75.5 μg per 100 g), ethanol (58.0 μg per 100 g), and butanone-2 (3.6–3.8 μg per 100 g). The thermophilic streptococcus and lactobacillus cultures, and the starter cultures contained predominantly acetic, butyric and caproic acids. Received 19 June 1997/ Accepted in revised form 10 January 1998     

Marine bacterial isolates inhibit biofilm formation and disrupt mature biofilms of Pseudomonas aeruginosa PAO1

According to the Centers for Disease Control and Prevention, biofilms cause 65% of infections in developed countries. Pseudomonas aeruginosa biofilm cause life threatening infections in cystic fibrosis infection and they are 1,000 times more tolerant to antibiotic than the planktonic cells. As quorum sensing, hydrophobicity index and extracellular polysaccharide play a crucial role in biofilm formation, extracts from 46 marine bacterial isolates were screened against these factors in P. aeruginosa. Eleven extracts showed antibiofilm activity. Extracts of S6-01 (Bacillus indicus = MTCC 5559) and S6-15 (Bacillus pumilus = MTCC 5560) inhibited the formation of PAO1 biofilm up to 95% in their Biofilm Inhibitory Concentration(BIC) of 50 and 60 μg/ml and 85% and 64% in the subinhibitory concentrations (1/4 and 1/8 of the BIC, respectively). Furthermore, the mature biofilm was disrupted to 70–74% in their BIC. The antibiofilm compound from S6-15 was partially purified using solvent extraction followed by TLC and silica column and further characterized by IR analysis. Current study for the first time reveals the antibiofilm and antiquorum-sensing activity of B. pumilus, B. indicus, Bacillus arsenicus, Halobacillus trueperi, Ferrimonas balearica, and Marinobacter hydrocarbonoclasticus from marine habitat.     

Bio-optical Characteristics and the Vertical Distribution of Photosynthetic Pigments and Photosynthesis in an Artificial Cyanobacterial Mat

Abstract Zonations of photosynthesis and photopigments in artificial cyanobacterial mats were studied with (i) oxygen and pH microsensors, (ii) fiber-optic microprobes for field radiance, scalar irradiance, and PSII fluorescence, and (iii) a light microscope equipped with a spectrometer for spectral absorbance and fluorescence measurements. Our analysis revealed the presence of several distinct 1–2 mm thick cyanobacterial layers mixed with patches of anoxygenic photosynthetic bacteria. Strong attenuation of visible light confined the euphotic zone to the uppermost 3 mm of the mat, where oxygen levels of 3–4 times air saturation and a pH peak of up to pH 8.8 were observed under saturating irradiance (413 μmol photon m⁻² s⁻¹). Oxygen penetration was 5 mm in light and decreased to 1 mm in darkness. Volumetric oxygen consumption in the photic and aphotic zones of illuminated mat was 5.5 and 2.9 times higher, respectively, than oxygen consumption in dark incubated mats. Scalar irradiance reached 100–150% of incident irradiance in the upper 0.5 mm of the mat due to intense scattering in the matrix of cells, exopolymers, and carbonate precipitates. In deeper mat layers scalar irradiance decreased nearly exponentially, and highest attenuation coefficients of 6–7 mm⁻¹ were found in cyanobacterial layers, where photosynthesis and photopigment fluorescence also peaked. Visible light was attenuated >100 times more strongly than near infrared light. Microscope spectrometry on thin sections of mats allowed detailed spectral absorbance and fluorescence measurements at defined positions relative to the mat surface. Besides strong spectral signals of cyanobacterial photopigments (Chl a and phycobiliproteins), the presence of both green and purple photosynthetic bacteria was evident from spectral signals of Bchl a and Bchl c. Microprofiles of photopigment absorbance correlated well with microdistributions of phototrophs determined in an accompanying study. Received: 20 December 1999; Accepted: 10 June 2000; Online Publication: 28 August 2000     

Ecological studies of Chloroflexis,a gliding photosynthetic bacterium

Summary Chloroflexis, a gliding, filamentous, photosynthetic bacterium, is present in the stratified algal-bacterial mats which occur in the 50°–70°C temperature range of alkaline hot spring effluents. The organism is in association with the alga in the upper, algal layer, and also forms thick, orange mats beneath the algal layer. Natural populations of Chloroflexis from these mats demonstrated light-stimulated uptake of some ¹⁴C-labelled organic compounds. Photosynthetic ¹⁴CO₂ fixation by natural samples of Chloroflexis was investigated with respect to temperature, light intensity and mat depth. Bacterial photosynthesis was determined in samples in which algae were present by use of the inhibitor 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU). Bacterial photosynthesis was maximal at depths down to about 3 mm and then decreased rapidly to very low levels at greater depths. The greatest amounts of bacteriochlorophyll pigments were also concentrated in the top 3–4 mm of the mat. The optimum light intensity for bacterial photosynthesis (about 400 ft-c) was considerably lower than the normal summer light intensity at the surface of the mat (5000-8000 ft-c).The temperature optima for photosynthesis by the bacterial component of natural mat samples from several sites of different temperatures in a hot spring thermal gradient were determined. Temperature optima approximated the environmental temperatures, indicative of the occurrence of strains of Chloroflexis adapted to different temperatures. Although bacterial standing crop was greatest in the temperature range 50°–55°C, maximum photosynthetic efficiency was observed at about 45°C. Sulfide was stimulatory to photosynthetic ¹⁴CO₂ fixation by naturally occurring populations of Chloroflexis under field conditions. These data are consistent with the hypothesis that Chloroflexis may utilize sulfide as an electron donor for photosynthetic CO₂ reduction. However, it is also likely that Chloroflexis grows photoheterotrophically in these mats, obtaining organic compounds from algal excretory products.     

Phylogenetic and Physiological Diversity of Bacteria Isolated from Puruogangri Ice Core

The microbial abundance, the percentage of viable bacteria, and the diversity of bacterial isolates from different regions of a 83.45-m ice core from the Puruogangri glacier on the Tibetan Plateau (China) have been investigated. Small subunit 16S rRNA sequences and phylogenetic relationships have been studied for 108 bacterial isolates recovered under aerobic growth conditions from different regions of the ice core. The genomic fingerprints based on ERIC (enterobacterial repetitive intergenic consensus)-polymerase chain reaction and physiological heterogeneity of the closely evolutionary related bacterial strains isolated from different ice core depths were analyzed as well. The results showed that the total microbial cell, percentages of live cells, and the bacterial CFU ranged from 10⁴ to 10⁵ cell ml⁻¹ (Mean, 9.47 × 10⁴; SD, 5.7 × 10⁴, n = 20), 25–81%, and 0–760 cfu ml⁻¹, respectively. The majority of the isolates had 16S rRNA sequences similar to previously determined sequences, ranging from 92 to 99% identical to database sequences. Based on their 16S rRNA sequences, 42.6% of the isolates were high-G + C-content (HGC) gram-positive bacteria, 35.2% were low-G + C (LGC) gram-positive bacteria, 16.6% were Proteobacteria, and 5.6% were CFB group. There were clear differences in the depth distribution of the bacterial isolates. The isolates tested exhibited unique phenotypic properties and high genetic heterogeneity, which showed no clear correlation with depths of bacterial isolation. This layered distribution and high heterogeneity of bacterial isolates presumably reflect the diverse bacterial sources and the differences in bacteria inhabiting the glacier’s surface under different past climate conditions.     

Investigations into the occurrence of alkaloids in ergot and single sclerotia from the 2007 and 2008 harvests

As a contribution to the occurrence of ergot alkaloids in ergot from German rye and triticale, samples from the 2007 and 2008 harvests were analyzed. Twelve alkaloids—six pairs of main alkaloids and their corresponding epimers—were determined in extracts prepared under alkaline conditions by HPLC with fluorescence detection without preceding purification. The total alkaloid content was found to be 0.03–0.18% in ergot from rye (n = 19) and 0.06–0.22% in ergot from triticale (n = 4), respectively. Furthermore, single sclerotia (n = 40) were investigated in terms of alkaloid content and distributional pattern. The main alkaloids in ergot were ergocristine, ergotamine and ergocornine, although the alkaloid composition was highly variable. Presented in part at the 30th Mykotoxin-Workshop, Utrecht, The Netherlands, April 28–30, 2008     

Antibacterial Activities of Novel Diselenide-bridged <Emphasis Type="Italic">bis</Emphasis>(Porphyrin)s on <Emphasis Type="Italic">Staphylococcus aureus</Emphasis> Investigated by Microcalorimetry

The actions of two novel diselenide-bridged bis(porphyrin)s (1 and 2) on Staphylococcus aureus growth was investigated by microcalorimetry at 37.00°C, compared with that of Na₂SeO₃. Differences in their capacities to inhibit the growth metabolism of S. aureus were observed. By analyzing the power–time curves, crucial parameters such as the rate constant of bacterial growth (k), inhibitory rate (I), and generation time (t _G) were determined. The growth rate constant (k) of S. aureus (in the log phase) in the presence of the drugs decreased with increasing concentrations of the drugs regularly. The relationship of k and c is nearly linear for diselenide-bridged bis(porphyrin) 2. The sequence of the antibacterial activities of these selenium compounds tested was 2 > 1 > Na₂SeO₃.     

Antipathogenic potential of marine <Emphasis Type="Italic">Bacillus</Emphasis> sp. SS4 on <Emphasis Type="Italic">N</Emphasis>-acyl-homoserine-lactone-mediated virulence factors production in <Emphasis Type="Italic">Pseudomonas aeruginosa</Emphasis> (PAO1)

Antipathogenic therapy is an outcome of the quorum-sensing inhibition (QSI) mechanism, which targets autoinducer-dependent virulent gene expression in bacterial pathogens. N-acyl homoserine lactone (AHL) acts as a key regulator in the production of virulence factors and biofilm formation in Pseudomonas aeruginosa PAO1 and violacein pigment production in Chromobacterium violaceum. In the present study, the marine bacterial strain SS4 showed potential QSI activity in a concentration-dependent manner (0.5–2 mg/ml) against the AHL-mediated violacein production in C. violaceum (33–86%) and biofilm formation (33–88%), total protease (20–65%), LasA protease (59–68%), LasB elastase (36–68%), pyocyanin (17–86%) and pyoverdin productions in PAO1. The light and confocal laser scanning microscopic analyses confirmed the reduction of the biofilm-forming ability of PAO1 when treated with SS4 extract. Furthermore, the antibiofilm potential was confirmed through static biofilm ring assay, in which ethyl acetate extract of SS4 showed concentration-dependent reduction in the biofilm-forming ability of PAO1. Thus, the result of this study clearly reveals the antipathogenic and antibiofilm properties of the bacterial isolate SS4. Through 16S rDNA analysis, the strain SS4 was identified as Bacillus sp. (GenBank Accession Number: GU471751).     

Antioxidant Properties of Selected <Emphasis Type="Italic">Boletus</Emphasis> Mushrooms

Considering the growing interest for mushrooms and the demand search of natural antioxidants sources, the aim of this study was to investigate the antioxidant properties of two edible widely used Boletus species, Boletus edulis, and Boletus auranticus, collected from Istra region in Croatia in late summer 2007. To evaluate the antioxidant properties and content of antioxidant compounds, scavenging capacity on DPPH˙, OH˙, and O₂˙⁻ radicals, reducing power and capacity to inhibit lipid peroxidation has been investigated. It is determined that content of total phenols (41.82 ± 0.08 mg gallic acid equivalent per gram of dry extract) was higher for B. edulis. Using high performance liquid chromatography/diode array detector analysis, the main antioxidant compound, variegatic acid, has been detected and quantified. 1,1-Diphenyl-2-picryl-hydrazyl-hydrate assay was used as a preliminary free radical–scavenging evaluation. By this assay, it has been found that B. edulis dry mushroom extract exhibits 50% of inhibition value at the extract concentration of 0.016 ± 0.0003 mg/ml. The extracts were capable of reducing iron(III) and, thus, are capable of donating electrons. Using electron paramagnetic resonance spin-trapping and spin-probing techniques, activity against relevant reactive species, ˙OH and O₂˙⁻ radical, was analyzed for both mushroom extracts. Both investigated extracts are determined as good inhibitors for ˙OH radical reduction, and both exhibited significant capacity for scavenging O₂˙⁻ radical and for that could help to prevent or meliorate oxidative damage. Only B. edulis extract prevents lipid peroxidation. Investigated mushroom extracts could represent easily accessible natural antioxidant resource.