COMPOSITION OF EXTRACELLULAR POLYMERIC SUBSTANCES FROM PERIPHYTON ASSEMBLAGES IN THE FLORIDA EVERGLADES1

In wetland habitats, periphyton is a common component of open‐water areas with species assemblage determined by local water quality. Extracellular polymeric substances (EPS) secreted by algae and bacteria give structure to periphyton, and differences in EPS chemistry affect the functional roles of these polymers. The Florida Everglades provide a unique opportunity to study compositional differences of EPS from distinctive algal assemblages that characterize areas of differing water chemistry. Water conservation area (WCA)‐1 is a soft‐water impoundment; periphyton was loosely associated with Utricularia stems and amorphous in structure, with a diverse desmid and diatom assemblage, and varying cyanobacterial abundance. Extracellular polymers were abundant and were loosely cell‐associated sheaths and slime layers in addition to tightly cell‐associated capsules. The EPS were complex heteropolysaccharides with significant saccharide residues of glucose, xylose, arabinose, and fucose. Carboxylic acids were also prominent, while ester sulfates and proteins were small components. Structured, cohesive cyanobacteria‐dominated periphyton was observed in WCA‐2A, a minerotrophic impoundment, and filaments were heavily encrusted with calcium carbonate and detrital matter. EPS were primarily cell‐associated sheaths, and polymer residues were dominated by glucose, xylose, fucose, and galactose, with uronic acids also a significant component of the polymers. Principal components analysis revealed that periphyton community assemblage determined the monosaccharide composition of EPS, which ultimately determines a range of biogeochemical processes within the periphyton.     

Carbon and Nitrogen Mineralization of Lead Treated Soils in the Eastern Mediterranean Region,Turkey

The aim of this study was to determine the first effect of lead on microbial activity in soil. The study was carried out in the soil samples from four different radish (Raphanus sativus L. var. radicula, Brassicaceae) fields along the highway in a district (Kadirli, Osmaniye) of the Eastern Mediterranean Region, Turkey. After the calculation of Pb contents, the Pb amounts of the soil samples were brought up to 50 and 100 mg Pb kg^?1 by treatment with Pb(NO ₃ ) ₂ , and the samples for the carbon and the nitrogen mineralization were incubated under controlled conditions (28°C, constant moist). The carbon mineralization was determined by a CO ₂ respiration method for 30 days. The nitrogen mineralization was observed in vitro for 6 weeks. The untreated group was statistically different from the 50 and 100 mg Pb kg^?1 treatments in the aspect of the C(CO ₂ ) outlet during mineralization (P ≤ 0.05), but difference between the 50 and 100 mg Pb kg^?1 treatments was not significant. NH ₄ -N and NO ₃ -N contents of each soil were shown differences between across treatments. Based on these results, it is possible to conclude that the addition of 50 and 100 mg Pb kg^?1 provided a toxic effect threshold for the microbial activity into 30 days.     

Incidence of mycoflora and mycotoxins in some edible fruits and seeds of forest origin

Twelve fungi namelyAlternaria alternata, Aspergillus flavus, A niger, A ochraceus, Actinomucor repens, Capnodoium spp., Curvularia lunata, Fusarium pallidoroseum, F solani, F verticillioides, Penicillium citrinum and Rhizopus stolonifer were recorded from samples ofAegle marmelos, Aesculus indica, Buchanania lanzan andPinus gerardiana. In case ofPrunus amygdalus only Rstolonifer was recorded. A significant variation in pattern of mycoflora incidence was observed in terms of source and season. Fungal infestation in most of the substrates was found to be highest during monsoon. Aflatoxins were the most common mycotoxins elaborated by different isolates ofA flavus obtained fromA marmelos, B lanzan andP gerardiana. The amount of aflatoxins produced by the toxigenic isolates ofA flavus was in the range of traces to 0.9–26.0 μg/ml inA marmelos, 0.8–17.5 μg/ml inP gerardiana and 0.65–13.2 μg/ml inB lanzan. The percentage toxigenicity was comparatively lower in the isolates of other mycotoxigenic fungi. Aflatoxins were detected almost in all the samples analyzed for mycotoxin contamination. However, traces of zearalenone were detected inA marmelos. The concentration of aflatoxin B₁ was in the range of 0.13–0.75 μg/g inA marmelos, 0.09–0.60 μg/g inP gerardiana and 0.01–0.20 ug/g inB lanzan. Mycotoxins were not detected inAesculus indica andPrunus amygdalus.     

Substance P-immunoreactive neurons in the brainstem of the cat related to cardiovascular centers

Summary The distribution of substance P-immunoreactivity (SP-IR) in the brainstem and spinal cord of normal and colchicine-pretreated cats was analysed using the peroxidase-antiperoxidase (PAP) technique. Numerous SP-IR fibers are present in the nucleus solitarius, nucleus dorsalis nervi vagi and nucleus spinalis nervi trigemini, various parts of the formatio reticularis, substantia grisea centralis mesencephali, locus coeruleus and nucleus parabrachialis. SP-IR perikarya occur in the substantiae gelatinosa and intermedia of the spinal cord, the nucleus spinalis nervi trigemini-pars caudalis, the nucleus dorsalis nervi vagi, and the nucleus solitarius, as well as in the adjacent formatio reticularis and the medullary nuclei of the raphe. In addition, SP-IR cell bodies are located in the nuclei raphe magnus and incertus, ventral and dorsal to the nucleus tegmentalis dorsalis (Gudden), nucleus raphe dorsalis, substantia grisea centralis mensencephali, locus coeruleus, nucleus parabrachialis and colliculus superior.The results indicate that SP-IR neurons may be involved in the regulation of cardiovascular functions both at the central and peripheral level. A peripheral afferent portion seems to terminate in the nucleus solitarius and an efferent part is postulated to originate from the nucleus dorsalis nervi vagi and from the area of the nuclei retroambiguus, ambiguus and retrofacialis.     

Pleurotaenium trabecula,a desmid of wetland biofilms: the extracellular matrix and adhesion mechanisms1

Pleurotaenium trabecula (Ehren.) Nägeli is a placoderm desmid that commonly occurs in wetland biofilms of the southeastern Adirondacks (NY, USA). It often displays a distinctive habit whereby the cell remains attached to the substrate via the polar end of one semicell, while the remainder of the cell is suspended in the water column. In this study, we examined the extracellular matrix (ECM) of this alga to elucidate its adhesion mechanisms and postadhesion behavior. The ECM consists of the following: (i) an extracellular polymeric substance (EPS), which includes polyanionic and sulfated polysaccharides; (ii) a thin pectin‐containing primary cell wall, which is quickly sloughed off after postcytokinetic semicell expansion; and (iii) a thick secondary cell wall that is perforated with a distinct pore complex. Each pore of this complex possesses an external network of densely aggregated fibrils. Selective solubilization and immunolabeling studies suggest that these fibrillar aggregates or “adhesion centers” (i.e., ACs) contain arabinogalactan protein and are involved in initial adhesion of the cell to a substrate. We propose that postinitial adhesion behavior entails localized secretion of EPS derived from a large pool of EPS‐containing vesicles situated in the peripheral cytoplasm. As the EPS absorbs water, hygroscopic pressure breaks the connections between the ACs on the cell wall and substrate and allows a portion of a cell to lift up into the water column.     

An improved method for the hydrolysis of hardwood carbohydrates to monomers

The range of xylan content reported for sugar maple (Acer saccharum) is wider than for most hardwoods. Credible values have been reported that range from less than 16 wt% to more than 19 wt% based on extractive-free wood. Carbohydrate composition of biomass is normally determined by a two stage H₂SO₄ hydrolysis followed by quantification of the sugar monomers. Acetic and uronic acids are also quantified for xylan-rich materials. In this research, the H₂SO₄ hydrolysis conditions were modified and an average xylan content of 18.7% was obtained for sugar maple with a standard deviation (SD) of 0.41% for eight analyses. Minor refinements were made and an average of 18.6% (SD = 0.29%) was obtained for another eight analyses. On this occasion the acetyl to xylose mole ratio was 0.71 with a standard deviation of only 0.008. Proton NMR was utilized in quantifying sugar monomers and acetic acid. The modified hydrolysis procedure gave all the expected results for Betula papyrifera, a species without much controversy regarding its carbohydrate composition. A high percentage of glucan plus xylan was also obtained for an experimentally grown poplar with a low lignin content of 17.7%. The summative analyses varied from 99.7% to 101.5% for the three species.