Biodegradation of free phytol by bacterial communities isolated from marine sediments under aerobic and denitrifying conditions.
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Biodegradation of (E)-phytol [3,7,11, 15-tetramethylhexadec-2(E)-en-1-ol] by two bacterial communities isolated from recent marine sediments under aerobic and denitrifying conditions was studied at 20 degrees C. This isoprenoid alcohol is metabolized efficiently by these two bacterial communities via 6,10, 14-trimethylpentadecan-2-one and (E)-phytenic acid. The first step in both aerobic and anaerobic bacterial degradation of (E)-phytol involves the transient production of (E)-phytenal, which in turn can be abiotically converted to 6,10,14-trimethylpentadecan-2-one. Most of the isoprenoid metabolites identified in vitro could be detected in a fresh sediment core collected at the same site as the sediments used for the incubations. Since (E)-phytenal is less sensitive to abiotic degradation at the temperature of the sediments (15 degrees C), the major part of (E)-phytol appeared to be biodegraded in situ via (E)-phytenic acid. (Z)- and (E)-phytenic acids are present in particularly large quantities in the upper section of the core, and their concentrations quickly decrease with depth in the core. This degradation (which takes place without significant production of phytanic acid) is attributed to the involvement of alternating beta-decarboxymethylation and beta-oxidation reaction sequences induced by denitrifiers. Despite the low nitrate concentration of marine sediments, denitrifying bacteria seem to play a significant role in the mineralization of (E)-phytol. (+info)
Visualization and enumeration of marine planktonic archaea and bacteria by using polyribonucleotide probes and fluorescent in situ hybridization.
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Fluorescent in situ hybridization (FISH) using rRNA-specific oligonucleotide probes has emerged as a popular technique for identifying individual microbial cells. In natural samples, however, the signal derived from fluor-labeled oligonucleotide probes often is undetectable above background fluorescence in many cells. To circumvent this difficulty, we applied fluorochrome-labeled polyribonucleotide probes to identify and enumerate marine planktonic archaea and bacteria. The approach greatly enhanced the sensitivity and applicability of FISH with seawater samples, allowing confident identification and enumeration of planktonic cells to ocean depths of 3,400 m. Quantitative whole-cell hybridization experiments using these probes accounted for 90 to 100% of the total 4',6-diamidino-2-phenylindole (DAPI)-stained cells in most samples. As predicted in a previous study (R. Massana, A. E. Murray, C. M. Preston, and E. F. DeLong, Appl. Environ. Microbiol. 63:50-56, 1997), group I and II marine archaea predominate in different zones in the water column, with maximal cell densities of 10(5)/ml. The high cell densities of archaea, extending from surface waters to abyssal depths, suggest that they represent a large and significant fraction of the total picoplankton biomass in coastal ocean waters. The data also show that the vast majority of planktonic prokaryotes contain significant numbers of ribosomes, rendering them easily detectable with polyribonucleotide probes. These results imply that the majority of planktonic cells visualized by DAPI do not represent lysed cells or "ghosts," as was suggested in a previous report. (+info)
Slow growth rate of a deep-sea clam determined by 228Ra chronology.
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The age of a deep-sea clam, Tindaria callistiformis, from 3803 m depth has been determined by 228Ra (6.7 year half-life) chronology of separated size fractions of a captured population. A length of 8.4 mm is attained in about 100 years. Shells of this size fraction show about 100 regularly spaced bands, indicating that the growth feature may be an annual one. (+info)
Studies on Cercariae from Kuwait Bay. XI. Description and surface topography of Cercaria kuwaitae XI sp.n. (Digenea: Echinostomatidae).
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A new echinostome cercaria, Cercaria kuwaitae XI sp.n., from the prosobranch gastropod Cerithidea cingulata (Gmelin) from Kuwait Bay is described. The new cercaria is characterized by 23 collar spines and primary excretory tubules with distinct diverticula. The cercaria encysts in the snail host and is similar to those of Acanthoparyphium sp. The surface topography of the redia, cercaria and metacercarial cyst wall is studied by scanning electron microscopy. This is the first echinostome cercaria to be recorded in a gastropod from the Arabian Gulf region. (+info)
Microbial diversity in marine sediments from Sagami Bay and Tokyo Bay, Japan, as determined by 16S rRNA gene analysis.
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16S rDNA clone libraries were analysed to investigate the microbial diversity in marine sediments from Sagami Bay (stations SA, water depth of 1159 m, and SB, 1516 m) and Tokyo Bay (station TK, 43 m). A total of 197 clones was examined by amplified rDNA restriction analysis (ARDRA) using three four-base-specific restriction enzymes (Hhal, Rsal and Haelll). In SA, 57 RFLP types were detected from 77 clones. In SB, 17 RFLP types were detected from 62 clones. In TK, 21 RFLP types were detected from 58 clones. The genotypic diversity among the three sampling sites was 0.958, 0.636 and 0.821, respectively, indicating that the microbial diversity of SA was higher than at the other two stations. At SA, the most abundant RFLP type constituted 10% of all clones. The samples from SB and TK had dominant RFLP types which constituted 60% and 38% of the total clone libraries, respectively. The community structure of SA included many single-type clones, which were found only once in the clone libraries. This structure contrasted with that of the other two stations. Thirty-seven clones were selected and sequenced according to dendrograms derived from ARDRA, to cover most of the microbial diversity in the clone libraries. No clones were identical to any of the known 165 rRNA sequences or to each other. All sequences had >84.8% similarity to rDNA sequences retrieved from the DNA databases. Sequenced clones fell into five major lineages of the domain Bacteria: the gamma, delta and epsilon Proteobacteria, Gram-positive bacteria and the division Verrucomicrobia. At SA, the Verrucomicrobia and the three subclasses of the Proteobacteria were found. Most clone sequences belonged to the gamma Proteobacteria. The high-GC Gram-positive bacteria and the gamma subclass of the Proteobacteria were common at both SB and TK. Although the depths of SB and TK were very different, the community diversity inferred from ARDRA and the taxonomic position of the dominant clones were similar. All clones belonging to the highGC Gram-positive bacteria collected from both SB and TK fell into the same cluster and are regarded as members of an unknown actinomycete group. The clone compositions were different at each sampling site, and clones of the gamma Proteobacteria and high-GC Gram-positive bacteria were dominant. (+info)
Role of metallothionein against oxidative stress in the mussel Mytilus galloprovincialis.
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Metallothionein (MT) is a sulfhydryl-rich protein involved mainly in heavy metal homeostasis and detoxification. In this study, the use of the mussel as an experimental model allowed us to test MT antioxidant properties at the molecular, cellular, and organism level. MT induction was achieved by mussel exposure to Cd (200 microg/l) in aquaria for 7 days followed by detoxification in the sea for 28 days. Cd-preexposed and nonexposed mussels were then treated with Fe (300-600 microg/l) in aquaria for 3 days. Biochemical assays on digestive gland tissue showed that treatment with Fe led to a significant increase in oxyradical production and malondialdehyde level only in mussels not preexposed to Cd. The Cd-dependent resistance to oxidative stress was ascribed to MT induction, as Cd produced no significant variation of reduced glutathione and major antioxidant enzymes. Digital imaging of isolated digestive gland cells showed lower oxyradical rise and higher viability in cells from Cd-preexposed mussels after treatments with 0.5-5 mM H2O2. Analyses on whole organisms showed that anoxic survival was lowered in mussels that had been treated with Fe, but such an effect was less pronounced in Cd-preexposed mussels compared with nonpreexposed ones. In conclusion, data suggest an antioxidant role for MT, which seems to occur through oxyradical scavenging and is able to protect both isolated cells and the entire organism from oxidative stress. (+info)
Turning on of activities in unfertilized sea urchin eggs: correlation with changes of the surface.
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Unfertilized sea urchin eggs exposed to low concentrations of ammonia enter into a number of activities which normally appear after fertilization. It is shown that the effects are attributable to ammonia, rather than to NH4+ ions of elevated pH. The same effects are obtained by exposure to isotonic urea and to glycerol at very low ionic strengths. All treatments which produce these changes (such as the turning on of chromosome replication and condensation in unfertilized eggs) also bring about changes of the outer cell surface which are visible in the scanning electron microscope. The most striking indicator is the elongation of the microvilli which cover the surface of the unfertilized egg. The changes of the surface are interpreted as the dissociation of a component from the outer surface layer. This component is not the "vitelline" sheet as defined morphologically or by the ability of the egg to form a fertilization membrane upon insemination. It is proposed further that this component is a peripheral component of the plasma membrane, whose removal modifies the membrane functionally and leads to the derepression of various processes within the egg. (+info)
Na(+) and Ca(2+) pumps in the gills, epipodites and branchiostegites of the european lobster Homarus gammarus: effects of dilute sea water.
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Crude homogenates and plasma-membrane-enriched fractions were prepared from the epithelium of the gills, epipodites and branchiostegites of intermoult European lobsters Homarus gammarus, and Na(+)/K(+)-ATPase, Ca(2+)-ATPase and Na(+)/Ca(2+) exchange activities were quantified in these tissues. Lobsters were kept in sea water (salinity 35 ) or were adapted to dilute sea water (22.1 ). The lobster hyperregulates haemolymph osmolarity and Ca(2+) levels in both media. Homogenates of the podobranchs, arthrobranchs and pleurobranchs had comparable Na(+)/K(+)-ATPase specific activities, and mean activities increased significantly for all three types of gills when the animals were kept in dilute sea water. In the epipodites and branchiostegites, Na(+)/K(+)-ATPase specific activities exceeded those in the gills, and exposure to dilute sea water greatly enhanced these activities. In sea water, 80 % of the total Na(+)/K(+)-ATPase activity is associated with the gills and epipodites (each tissue containing 40 %) and 20 % with the branchiostegites; in dilute sea water, the gills contained approximately 25 %, the epipodites 40 % and the branchiostegites approximately 35 % of the total activity, indicating the relative importance of the epipodites and branchiostegites for ionic hyperregulation in dilute media. In plasma membrane vesicles isolated from the gills, epipodites and branchiostegites, Ca(2+) transport driven by ATP and by a Na(+ )gradient was demonstrated. Exposure to dilute sea water enhanced Na(+)/Ca(2+ )exchange and Ca(2+)-ATPase activities in the epipodites and branchiostegites; in the gills, however, Ca(2+) transport activities decreased. The role of these tissues and enzymes in Na(+) and Ca(2+) handling by the lobster is discussed. (+info)