Large p 5 0 0 pm), suspended particles of organic and inorganic material, often referred to as 'marine snow', are considered important in the vertical transport and biogeochemical transformation of particulate organic carbon in the marine environment. Previous work has indicated that bacterial species inhabiting marine snow particles may differ greatly from those commonly found living free in the surrounding water column. To further characterize marine-snow-attached bacterial populations, we sampled marine snow by SCUBA diving during periods of intense macroaggregate formation in the northern Adriatic Sea in August 1991. Small subunit ribosomal DNA (rDNA) fragments of bacteria were amplified from extracted nucleic acids by the polymerase chain reaction (PCR). The diversity of the recovered rDNA clones was initially assessed by c o r n p m g restriction fragment length polymorphisms (RFLPs) of individual clones. Ninety-five bacterial clones examined yielded 90 different KFLP patterns, representing an estimated sampling coverage of only 5.3%. Sequence analysis of 39 randomly chosen clones was used to assess the general phylogenetic affiliation of individual clones. Bacterial phyla represented in the library included affiliates of the Planctomyces, the Gram-positive bacteria, the Cytophaga-Flavobacteria-Bacteroides (CFB) lineage, and the alpha-, gamma-, delta-, and epsilon-subdivisions of the Proteobacteria. The results suggest that bacterial colonization of suspended marine macroaggregates can result in diverse and complex assemblages, with specific phyla, such as the CFB, being commonly associated with marine particles. Futhermore, this particle-attached bacterial assemblage was similar to other bacterial assemblages found in marine sediments and terrestrial soils, with respect to the nature of the associated phylogenetic groups.

A PCR-based denaturing-gradient gel electrophoresis (DGGE) approach was applied to a partial sequence of the ␤-D-glucuronidase gene (uidA) for specific detection and differentiation of Escherichia coli populations according to their uidA sequence variations. Detection of sequence variations by PCR-DGGE and by PCR with direct sequencing correlated perfectly. Screening of 50 E. coli freshwater isolates and reference strains revealed 11 sequence types, showing nine polymorphic sites and an average number of pairwise differences between alleles of the uidA gene fragments (screened fragment length, 126 bp) of 2.3%. Among the analyzed strains a range of dominating to more rarely and/or uniquely observed E. coli sequence types was revealed. PCR-DGGE applied to fecally polluted river water samples simultaneously detected E. coli and generated a fingerprint of the mixed populations by separating the polymorphic uidA amplicons. No significant differences between non-cultivation-based and cultivation-based profiles were observed, suggesting that at least some members of all occurring sequence types could be cultivated. As E. coli is frequently used as a fecal indicator, this work is considered an important step towards a new, practical tool for the differentiation and tracing of fecal pollution in all kinds of waters.Escherichia coli contamination is a widely used parameter for the examination of various kinds of waters. The detection of E. coli in temperate freshwaters usually provides a reliable indication of fecal pollution from humans and warm-blooded animals (14, 33). Recently, efficient cultivation media for routine monitoring of E. coli in environmental freshwaters have been developed (2,9,20). Those methods are generally applied in a quantitative way to estimate the actual concentration of E. coli. No information about the qualitative composition of different strains and clones can be gained (3,14). Differentiation is not the main purpose for most routine applications, although there is a considerable demand for techniques for the simultaneous detection and differentiation of E. coli populations in aquatic habitats. A practical method generating a representative genetic fingerprint of population structures would enable routinely performed qualitative investigations such as the comparison of different sources of fecal emissions (e.g., effluents from different sewage treatment plants or human versus nonhuman fecal pollution).Several methods are available for the identification, characterization, and typing of microorganisms (34). So far, serotyping, biotyping, multilocus enzyme electrophoresis (MLEE), profiling for insertion elements and plasmids, restriction fragment length polymorphism analysis, random amplified polymorphic DNA analysis, amplified restriction fragment polymorphism analysis, ribotyping, pulsed-field gel electrophoresis, DNA sequencing, and detection of a genome polymorphism marker by PCR have been used for typing of E. coli cells, representing low-to high-range resolution techniques (8, 13, 16, 17,...

Bacterial biomass, potential bacterial production and ectoenzymatic activity were measured at 4 stations along a trophic gradient at the Atlantic Barrier Reef off Belize (Central America). We investigated the changes in the trophic status of this system, which we hypothesized would also lead to changes in the bacterial community. The bacterial community of the oligotrophic station was characterized by low biomass (mean 7.2 pg C 1-') and low potential production rates (mean 9.2 pg C l-Id-') as determined by seawater cultures whereas at the most eutrophic station bacterial biomass (mean 18.6 pg C I-') as well as potential bacterial production (mean 15.5 pg C I-' d-l) was significantly higher. Oligotrophic bacteria exhibit high potential turnover rates (1.5 d-l). Ectoenzymatic activity measurements with fluorogenic-substrate analogs showed distinct differences in the expression of certain enzymes at different trophic conditions. a-and P-D-glucosidase activity declined from eutrophic to oligotrophic in both per volume and per cell while leucine-aminopeptidase activity per cell was inversely correlated with the trophic status of the environment. Differences in ectoenzymatic activity are indicated by differences in both v,,,,, and K, . K,,, values of leucine-aminopeptidase clearly reflect the trophic situation. Substrate affinity was found to be higher in oligotrophic waters by 2 orders of magnitude as compared to eutrophic environments. Potential activity (v,,,,) of the extracellular enzymes tested was found to be correlated to potential bacterial production and bacterial biomass.

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This paper provides an overview of the various dual-use concepts applied in national and international non-proliferation and anti-terrorism legislation, such as the Biological and Toxin Weapons Convention, the Chemical Weapons Convention and United Nations Security Council Resolution 1540, and national export control legislation and in relevant codes of conduct. While there is a vast literature covering dual-use concepts in particular with regard to life sciences, this is the first paper that incorporates into such discussion the United Nations Security Council Resolution 1540. In addition, recent developments such as the extension of dual-use export control legislation in the area of human rights protection are also identified and reviewed. The discussion of dual-use concepts is hereby undertaken in the context of human- and/or national-security-based approaches to security. This paper discusses four main concepts of dual use as applied today in international and national law: civilian versus military, peaceful versus non-peaceful, legitimate versus illegitimate and benevolent versus malevolent. In addition, the usage of the term to describe positive technology spin-offs between civilian and military applications is also briefly addressed. Attention is also given to the roles civil society and research ethics may play in the governance of dual-use sciences and technologies.