We examined diel trends in internal pools and net efflux of free amino acids in colonies of the nonheterocystous, diazotrophic cyanobacterium Trichodesmium thiebautii, freshly collected from waters of the Caribbean and the Bahamas. The kinetics of glutamate uptake by whole colonies were also examined. While intracolonial pools of most free amino acids were relatively constant through the day, pools of glutamate and glutamine varied over the diel cycle, with maxima during the early afternoon. This paralleled the daily cycle of nitrogenase activity. We also observed a large net release of these two amino acids from intact colonies. Glutamate release was typically 100 pmol of N colony-' h-1. This is about one-fourth the concurrent rate of N2 fixation during the day. However, while nitrogenase activity only occurs during the day, net release of glutamate and glutamine persisted into the night and may therefore account for a greater loss of recently fixed N on a daily basis. This release may be an important route of new N input into tropical, oligotrophic waters. Whole colonies also displayed saturation kinetics with respect to glutamate uptake. The K, for whole colonies varied from 1.6 to 3.2 ,uM, or about 100-fold greater than typical ambient concentrations. Thus, uptake systems appear to be adapted to the higher concentrations of glutamate found within the intracellular spaces of the colonies. This suggests that glutamate may be a vehicle for N exchange among trichomes in the colony.

Aims: To evaluate the in¯uence of marine bacterial assemblages from the Bay of Fundy on Alexandrium fundyense str. CB301 growth. Methods and Results: Bacterial assemblages were collected from the Bay of Fundy during an Alexandrium spp. bloom, serially diluted to extinction and inoculated into axenic CB301 cultures. Bacterial assemblages dramatically enhanced CB301 growth. Retrieval and analysis of 16S rDNA fragments revealed an Alteromonas sp. strain to be the only detectable bacterium in all assemblages that promoted A. fundyense and the sole bacterium found in the most dilute inoculum that promoted A. fundyense. While this bacterium has not yet been isolated, other isolates obtained from the assemblages did not stimulate A. fundyense, indicating that the observed stimulation was not a general effect of marine bacteria. Conclusions: Bay of Fundy marine bacterial assemblages dominated by a member of the family Alteromonadaceae were found to dramatically stimulate growth of A. fundyense. Signi®cance and Impact of the Study: These results show that native bacteria have the potential to dramatically promote the growth of A. fundyense and may play an important role in in¯uencing A. fundyense dynamics in the Bay of Fundy.

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The algistatic properties of aqueous barley straw (Hordeum vulgare) extracts have been observed in laboratory studies and in situ. This reported algistatic property has been used by farmers and horticulturists to control algal blooms in various systems and has become standard practice in some areas. However, both inhibition and stimulation of algal growth in freshwater and marine species have been demonstrated. While the number of taxa known to be inhibited by barley straw has increased, comparatively little has been done to isolate and classify the compound(s) responsible for this algistatic effect. A microplate assay system using Microcystis aeruginosa was developed to isolate and identify the inhibitory components of barley straw extract. M. aeruginosa was selected for the bioassay because it is consistently inhibited by barley straw extract in studies conducted by our laboratory and others. The 24-well plate assay utilizes in vivo fluorescence monitoring with a TECAN GENios plate reader to determine chlorophyll-a levels in each culture. Fractionation and partial chemical characterization of inhibitory extracts suggests that the inhibitors are polyphenolics with molecular weights (MW) between 1,000 and 3,000 Da. Percolation of the aqueous extract through a Polyamide CC6 resin or through various MW cutoff filters resulted in the loss of algistatic activity, which confirms this assertion, while hydrolysis resulted in little change in the activity profile. Fractionation by HPLC methods yielded a highly potent multi-compound fraction, showing toxicity at 353 mg L −1 and algistatic activity between 11.1 and 3.53 mg L −1 .

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In vitro cultures of scarlet flax (Linum grandiflorum L.), an important ornamental flax, have been established as a new possible valuable resource of lignans and neolignans for antioxidant and anti-inflammatory applications. The callogenic potential at different concentrations of α-naphthalene acetic acid (NAA) and thidiazuron (TDZ), alone or in combinations, was evaluated using both L. grandiflorum hypocotyl and cotyledon explants. A higher callus induction frequency was observed on NAA than TDZ, especially for hypocotyl explants, with a maximum frequency (i.e., 95.2%) on 1.0 mg/L of NAA. The presence of NAA (1.0 mg/L) in conjunction with TDZ tended to increase the frequency of callogenesis relative to TDZ alone, but never reached the values observed with NAA alone, thereby indicating the lack of synergy between these two plant growth regulators (PGRs). Similarly, in terms of biomass, NAA was more effective than TDZ, with a maximum accumulation of biomass registered for medium supplemented with 1.0 mg/L of NAA using hypocotyls as initial explants (DW: 13.1 g). However, for biomass, a synergy between the two PGRs was observed, particularly for cotyledon-derived explants and for the lowest concentrations of TDZ. The influence of these two PGRs on callogenesis and biomass is discussed. The HPLC analysis confirmed the presence of lignans (secoisolariciresinol (SECO) and lariciresinol (LARI) and neolignan (dehydrodiconiferyl alcohol [DCA]) naturally accumulated in their glycoside forms. Furthermore, the antioxidant activities performed for both hypocotyl- and cotyledon-derived cultures were also found maximal (DPPH: 89.5%, FRAP 866: µM TEAC, ABTS: 456 µM TEAC) in hypocotyl-derived callus cultures as compared with callus obtained from cotyledon explants. Moreover, the anti-inflammatory activities revealed high inhibition (COX-1: 47.4% and COX-2: 51.1%) for extract of hypocotyl-derived callus cultures at 2.5 mg/L TDZ. The anti-inflammatory action against COX-1 and COX-2 was supported by the IC50 values. This report provides a viable approach for enhanced biomass accumulation and efficient production of (neo)lignans in L. grandiflorum callus cultures.

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