Lembehsterols A and B, novel sulfated sterols inhibiting thymidine phosphorylase, from the marine sponge Petrosia strongylata.
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Lembehsterols A (1) and B (2), two novel sulfated sterols, were isolated from the marine sponge Petrosia strongylata. Both sterols showed inhibitory activity against thymidine phosphorylase, which is an enzyme related to angiogenesis in solid tumors. The structures of these sulfated sterols were established on the basis of chemical and physicochemical evidence. (+info)
Use of 16S ribosomal DNA for delineation of marine bacterioplankton species.
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All of the marine bacterioplankton-derived 16S ribosomal DNA sequences previously deposited in GenBank were reanalyzed to determine the number of bacterial species in the oceanic surface waters. These sequences have been entered into the database since 1990. The rate of new additions reached a peak in 1999 and subsequently leveled off, suggesting that much of the marine microbial species richness has been sampled. When the GenBank sequences were dereplicated by using 97% similarity as a cutoff, 1,117 unique ribotypes were found. Of the unique sequences, 609 came from uncultured environmental clones and 508 came from cultured bacteria. We conclude that the apparent bacterioplankton species richness is relatively low. (+info)
Characterization of the conserved region of the mxaF gene that encodes the large subunit of methanol dehydrogenase from a marine methylotrophic bacterium.
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The highly conserved region of the mxaF gene that encodes the large subunit of methanol dehydrogenase (MDH) was cloned and sequenced from Methylophaga sp. strain MP cells. The calculated G + C content of the conserved region was found to be 44.9%. The nucleotide sequence homology of the region to those from methylotrophs was approximately 43.5%, while the identity of the deduced amino acid sequence to other MxaF peptides was approximately 76.8%. Analysis of the codon usage revealed that UUC and CGU codons seem to be used only for phenylalanine and arginine, respectively. The aligned amino acid sequences show that several key amino acids that are required for the MDH enzyme activity are located in the deduced MxaF peptide, together with tryptophan-docking motifs, called W4 and W5. (+info)
An automatic respirometer for determining oxygen uptake in crayfish (Austropotamobius pallipes (Lereboullet)) over periods of 3-4 days.
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1. An automatic respirometer has been developed for continuous measurements over 3-4 days on 1-15 g crayfish. The sensor is a modified Mackereth oxygen electrode. Respiration is recorded on a millivolt potentiometric pen recorder during closed periods when the O2 concentration in the medium falls to a predetermined level. A solenoid-operated valve is then opened via a relay circuit energized by a reed switch mounted on the recorder. Medium flows through the respirometer until the O2 concentration is raised back to another predetermined level. Artificial media containing little or no nutrient salts are used to restrict the growth of microbes. 2. Respiration was determined chiefly on crayfish (Austropotamobius pallipes) with body wet weights of 7-0-12-5 g at 10-0 degrees C. In unrestrained but relatively quiescent animals, standard metabolism is described by the regression equation, ln O2 uptake = 3-3037 + 1-002 ln body wt. In restless crayfish active metabolism is described by the equation, ln O2 uptake = 4-4412 + 0-861 ln body wt. (+info)
The signal transducer P(II) and bicarbonate acquisition in Prochlorococcus marinus PCC 9511, a marine cyanobacterium naturally deficient in nitrate and nitrite assimilation.
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The amino acid sequence of the signal transducer P(II) (GlnB) of the oceanic photosynthetic prokaryote Prochlorococcus marinus strain PCC 9511 displays a typical cyanobacterial signature and is phylogenetically related to all known cyanobacterial glnB genes, but forms a distinct subclade with two other marine cyanobacteria. P(II) of P. marinus was not phosphorylated under the conditions tested, despite its highly conserved primary amino acid sequence, including the seryl residue at position 49, the site for the phosphorylation of the protein in the cyanobacterium Synechococcus PCC 7942. Moreover, P. marinus lacks nitrate and nitrite reductase activities and does not take up nitrate and nitrite. This strain, however, expresses a low- and a high-affinity transport system for inorganic carbon (C(i); K(m,app) 240 and 4 micro M, respectively), a result consistent with the unphosphorylated form of P(II) acting as a sensor for the control of C(i) acquisition, as proposed for the cyanobacterium Synechocystis PCC 6803. The present data are discussed in relation to the genetic information provided by the P. marinus MED4 genome sequence. (+info)
Albidovulum inexpectatum gen. nov., sp. nov., a nonphotosynthetic and slightly thermophilic bacterium from a marine hot spring that is very closely related to members of the photosynthetic genus Rhodovulum.
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Several bacterial isolates, with an optimum growth temperature of about 50 degrees C, were recovered from the marine hot spring at Ferraria on the island of Sao Miguel in the Azores. The geothermal water emerged from a porous lava flow and rapidly cooled in contact with seawater except at low tide. The bacterial species represented by strains FRR-10(T) and FRR-11 was nonpigmented, strictly aerobic, and organotrophic. Several genes, bchZ, pufB, pufA, pufL, or pufM, encoding the photosynthetic reaction center proteins and the core light-harvesting complexes were not detected in these strains. The organism oxidized thiosulfate to sulfate with enhancement of growth. The organism did not require additional NaCl in the culture medium for growth, but NaCl at 1.0% enhanced growth. Phylogenetic analyses using the 16S rRNA gene sequence of strain FRR-10(T) indicated that the new organism represented a new species of the alpha-3 subclass of the Proteobacteria and that it branches within the species of the genus Rhodovulum. The contradiction of classifying an organism which branches within the radiation of the genus Rhodovulum but does not possess the hallmark characteristics of this genus is discussed. However, the absence of several of these characteristics, namely, the lack of photosynthesis and pigmentation, which could be related to colonization of dark environments, and growth at high temperatures, leads to our proposal that strains FRR-10(T) and FRR-11 should be classified as a new species of a novel genus, Albidovulum inexpectatum, representing, at present, the most thermophilic organism within the alpha-3 subclass of the Proteobacteria. (+info)
Molecular evidence for a uniform microbial community in sponges from different oceans.
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Sponges (class Porifera) are evolutionarily ancient metazoans that populate the tropical oceans in great abundances but also occur in temperate regions and even in freshwater. Sponges contain large numbers of bacteria that are embedded within the animal matrix. The phylogeny of these bacteria and the evolutionary age of the interaction are virtually unknown. In order to provide insights into the species richness of the microbial community of sponges, we performed a comprehensive diversity survey based on 190 sponge-derived 16S ribosomal DNA (rDNA) sequences. The sponges Aplysina aerophoba and Theonella swinhoei were chosen for construction of the bacterial 16S rDNA library because they are taxonomically distantly related and they populate nonoverlapping geographic regions. In both sponges, a uniform microbial community was discovered whose phylogenetic signature is distinctly different from that of marine plankton or marine sediments. Altogether 14 monophyletic, sponge-specific sequence clusters were identified that belong to at least seven different bacterial divisions. By definition, the sequences of each cluster are more closely related to each other than to a sequence from nonsponge sources. These monophyletic clusters comprise 70% of all publicly available sponge-derived 16S rDNA sequences, reflecting the generality of the observed phenomenon. This shared microbial fraction represents the smallest common denominator of the sponges investigated in this study. Bacteria that are exclusively found in certain host species or that occur only transiently would have been missed. A picture emerges where sponges can be viewed as highly concentrated reservoirs of so far uncultured and elusive marine microorganisms. (+info)
Unveiling the organisms behind novel eukaryotic ribosomal DNA sequences from the ocean.
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Despite the fact that the smallest eukaryotes (cells less than 5 micro m in diameter) play key roles in marine food webs, particularly in open oligotrophic areas, the study of their in situ diversity started just one year ago. Perhaps the most remarkable finding of the most recent studies has been the discovery of completely new phylogenetic lineages, such as novel clades belonging to the stramenopile and alveolate phyla. The two new groups account for a significant fraction of clones in genetic libraries from North Atlantic, equatorial Pacific, Antarctic, and Mediterranean Sea waters. However, the identities and ecological relevance of these organisms remain unknown. Here we investigate the phylogenetic relationships, morphology, in situ abundance, and ecological role of novel stramenopiles. They form at least eight independent clades within the stramenopile basal branches, indicating a large phylogenetic diversity within the group. Two lineages were visualized and enumerated in field samples and enrichments by fluorescent in situ hybridization using specific rRNA-targeted oligonucleotide probes. The targeted organisms were 2- to 3- micro m-diameter, round-shaped, nonpigmented flagellates. Further, they were found to be bacterivorous. One lineage accounted for up to 46% (average during an annual cycle, 19%) of heterotrophic flagellates in a coastal environment, providing evidence that novel stramenopiles are important and unrecognized components of the total stock of bacterial grazers. (+info)