An experimental recirculating aquaculture system was constructed under ambient seawater conditions to compare microbial community diversity of nitrifying and denitrifying biofilters that were derived from a commercial inoculum used for aquarium applications. Next generation sequencing revealed distinct and diverse microbial communities in samples analyzed from the commercial inoculant and the denitrification and nitrification biofilters. In all samples, communities were represented by a few dominant operational taxonomic units (OTUs). Bacteria having the capacity to carry out ammonia and nitrite oxidation were more abundant in the nitrification biofilter. Similarly, the proportion of the bacterial taxa known to carry out heterotrophic and autotrophic denitrification and participate in sulfur cycling were found in the denitrification bioreactor, and likely originated from the ambient environmental water source. Our results indicated that environmental seawater can be a favorable enhancement to the bacterial consortium of recirculating aquaculture systems biofilters.

A Planctomyces limnophilus mutant generated using the EZ-Tn5 transposome was found to possess an insertion within pckA, encoding phosphoenolpyruvate carboxykinase. Disruption of pckA expression and elimination of enzymatic activity resulted in poor growth in glucose-free medium, demonstrating a gluconeogenic role for pckA in P. limnophilus. Bacteria belonging to the phylum Planctomycetes possess several distinctive phenotypic and molecular characteristics, including a proteinaceous cell wall that is devoid of peptidoglycan (17), reproduction by yeast-like division, and in many cases, internal cell compartmentalization resembling the eukaryotic nucleus (2, 19). They are found in aquatic and soil environments (3), as well as among microbial communities associated with the intestinal tracts of many organisms, including mammals (11) and fish (15). The Planctomycetes are significant participants in the global carbon and nitrogen cycles and contain a unique group capable of carrying out anaerobic ammonium oxidation (anammox) (5,8). While the availability of genome sequences for several Planctomycetes (cited in reference 6), as well as biochemical, physiological, and ecological studies, have provided some insight into this fascinating group of bacteria, the lack of molecular genetic tools has made it difficult to examine them in greater detail.Recently, Jogler et al. (6) described a genetic approach for studying Planctomyces limnophilus and suggested that this bacterium be used as a model species for the Planctomycetes. P. limnophilus is a chemoheterotroph that has a distinct cell cycle, with sessile cells that form stalks; its ability to form multicellular rosettes, its low salt tolerance, pinkish red pigmentation, high growth rate compared to the growth of other Planctomycetes (4), intracytoplasmic membrane structure, and the availability of a genome sequence (10) make it an ideal subject for molecular genetic studies. We have been examining the use of the Epicentre (Madison, WI) R6K␥ori/Kan-2 transposon kit (EZ-Tn5) (9) for creating P. limnophilus mutants by a procedure similar to that described by Jogler et al. (6). Here, we report the isolation of mutants obtained using this approach and describe the characterization of one mutant that contains an insertion within the gene encoding phosphoenolpyruvate carboxykinase, pckA.Transposon mutagenesis and isolation of mutants. Electrocompetent cells of P. limnophilus (DSM 3776), a gift from Naomi Ward, University of Wyoming, were prepared from a 5-day-old culture grown in 500 ml of modified 621 medium (DSMZ) (peptone and yeast extract concentrations were doubled to 0.05% each) at 28°C and 190 rpm that was washed with 10% glycerol and suspended in 1.5 ml 10% glycerol. Cells prepared in this manner were electrocompetent for several months when stored at Ϫ80°C. Electroporation was carried out by mixing 1 l of EZ-Tn5 transposome solution and 1 l of TypeOne restriction inhibitor (Epicentre) with 70-l cells in a microcentrifuge tube, incubating on ice for 5 min, and then transf...

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Vessels, specifically ballast water and hull fouling, are a major vector for the introduction of non-indigenous species (NIS) in European seas. The Mediterranean is one of the world's marine regions where their invasion is heaviest. The shallow Adriatic basin is a highly sensitive area that is already experiencing its consequences. The secondary spread of NIS over a wider area through natural dispersion is a complex process that depends on a wide range of oceanographic factors. This work analysed the dataset of the BALMAS project, in whose framework twelve ports in the Adriatic Sea were subjected to a Port Baseline Survey (PBS), to estimate the natural spread of NIS organisms from their port of arrival to the wider Adriatic basin. Its findings indicate that the prevailing water circulation patterns facilitate the natural dispersal of harmful aquatic organisms and pathogens (HAOP).

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The objective of this study was to determine whether the use of the electromagnetic field (EMF) of 50 Hz frequency and magnetic induction of 0.25 T could make for successful inactivation of a phytoplankton species, namely, marine microalgae Tetraselmis suecica and two bacteria strains; Escherichia coli and Enterococcus faecalis. A number of laboratory electromagnetic field tolerance experiments with the selected organisms was performed; each microorganism was treated for various lengths of time; 1, 5 and 10 minutes, and in three various media with special regards to the conductivity. Bacteria were exposed to high, moderate and extremely low conductivity media, and the microalgae to high, low and extremely low conductivity media. The microbial viability was checked by counting the bacterial colony forming units, as well as alive and dead stained microalgae cells. It was found that the time of exposure to the EMF had a profound effect on the viability of T. suecica only in the extremely low conductivity media, and that it did not affect the viability of E. coli or E. faecalis at all. Sažetak Cilj ovoga istraživanja bio je utvrditi može li elektromagnetsko polje (EMP) frekvencije 50 Hz i magnetske indukcije od 0,25 T uspješno inaktivirati jednu morsku fitoplanktonsku vrstu; mikroalgu Tetraselmis suecica te dvije vrste bakterija; Escherichia coli i Enterococcus faecalis. Provedeni su laboratorijski pokusi tolerancije odabranih organizama na elektromagnetsko polje. Svaki mikroorganizam tretiran je u različitim razdobljima; 1, 5 i 10 minuta, te u tri različita medija s obzirom na vodljivost. Bakterije su bile izložene u mediju visoke, umjerene i ekstremno niske vodljivosti, a mikroalge u mediju visoke, niske i ekstremno niske vodljivosti. Mikrobna vijabilnost je ispitivana uz pomoć brojanja izraslih kolonija bakterija, te živih i mrtvih obojenih stanica mikroalgi. Utvrđeno je da je vrijeme izlaganja elektromagnetskom polju imalo velik utjecaj na vijabilnost T. suecica samo u mediju ekstremno niske vodljivosti i da nije uopće utjecalo na vijabilnost E. coli ili E. faecalis.