Link between Domoic Acid Production and Cell Physiology after Exchange of Bacterial Communities between Toxic Pseudo-nitzschia multiseries and Non-Toxic Pseudo-nitzschia delicatissima (original) (raw)
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Harmful Algae, 2004
The interaction between bacteria and phytoplankton is increasingly becoming recognised as an important factor in the physiology of toxin production and the dynamics of harmful algal blooms (HABs). Bacteria can play a direct or indirect role in the production of biotoxins once solely attributed to microalgae. Evidence implicating bacteria as an autonomous source paralytic shellfish poisoning biotoxins raises the question of autonomous bacterial toxigenesis of the neurotoxin domoic acid (DA), the cause of amnesic shellfish poisoning. Here, we examine whether the previously observed bacterial enhancement of DA production by Pseudo-nitzschia multiseries (Hasle) Hasle may be attributable to independent biotoxin production by the extra-cellular bacteria associated with this diatom. The growth and toxicity of six cultures of xenic P. multiseries clone CLN-1 were followed for 24 days. Up to day 14 (mid-stationary phase), DA production was not statistically different among culture flasks. On day 14, P. multiseries cells were removed by gentle filtration from a set of triplicate flasks, leaving the bacteria in the filtrate. Following the removal of the algal cells, DA in the filtrate ceased to increase. Instead, DA levels continuously declined. A follow-up experiment determined that this was likely caused by photodegradation rather than by bacterial degradation. We conclude that after removing P. multiseries cells, the extra-cellular bacteria remaining in the filtrate were incapable of autonomous DA toxigenesis, even in the presence of P. multiseries exudates. However, scanning electron microscopy revealed that P. multiseries cells harboured epiphytic bacteria, the importance of which can still not be ruled out in DA production. Crown
Natural Toxins, 1995
Axenic cultures of Pseudo-nitzschia multiseries (formerly Pseudonitzschia pungens f. multiseries) produce less domoic acid (DA) than the original bacteria-containing cultures. Bacterial strains isolated from two nonaxenic P. multiseries clones were reintroduced individually into cultures of three axenic P. multiseries strains. The bacteria did not substantially affect division rates or cell yields. However, they did cause a 2-to 95-fold enhancement of DA production (per cell basis) relative to the axenic culture, depending on the P. multiseries and bacterial strain used. Bacteria isolated from a nontoxic Chaetoceros sp. culture also enhanced DA per cell (by 115-fold), showing that it is not necessary for the bacteria to be isolated from a toxic culture in order to enhance toxin production. There was no evidence of intracellular bacteria in disrupted P. multiseries cells obtained from axenic cultures. Our results demonstrate an important, but nonessential, role of extracellular bacteria in DA production. Characterization of the bacterial strains using morphology, substrate utilization, and restriction fragment length polymorphism (RFLP) analysesclearly showed that we had isolated different species of bacteria from the various nonaxenic cultures. We conclude that not one but several bacterial species enhance DA production by P. multiseries.
Journal of Plankton Research, 2011
ABSTRACT Here we compare cell physiology and domoic acid (DA) production for two strains of the diatom Pseudo-nitzschia multiseries originating from two opposite latitudes: Canada (CA) and Brazil (BR). The algae were grown as chemostat cultures at 0.2, 0.3 and 0.4 day(-1) under nitrogen (N)- and phosphorus (P)-deficient conditions. The level of deficiency significantly affected the atomic C:N, C:P, C:Si and N:P ratios in both strains. In both strains, P per cell was 2-4 x higher in the N- than in the P-deficient cultures. The opposite was not found for N in the P-deficient cultures) as shown by the N:P ratios and C:N ratios. The C:N and C:P ratios were significantly lower in the CA strain, and this did not change due to the level of deficiency The concentration and production of DA per cell per day were significantly higher for both strains under P deficiency as expected since the toxin is rich in N. However, DA was also produced by both strains during continuous cell division under N deficiency High or low bacterial densities associated with P multiseries did not increase or decrease DA production. Our data imply that more attention needs to be given to the N:P ratios and concentrations in the waters where these algae occur, as both N and P deficiencies affect DA production and cellular DA concentrations.
Bacterial community composition differs with species and toxigenicity of the diatom Pseudo-nitzschia
Aquatic Microbial Ecology, 2011
Interactions between bacteria and members of the marine diatom genus Pseudonitzschia may enhance production of the toxin domoic acid (DA) by toxigenic strains of Pseudonitzschia. To gain a broader understanding of relationships between bacteria and Pseudo-nitzschia species, we used automated ribosomal intergenic spacer analysis (ARISA) to assess the composition of the bacterial communities coexisting with 18 Pseudo-nitzschia strains representing 6 species. For cultures surveyed across multiple time points and size fractions, the attached and free-living bacterial communities were not significantly distinct from one another, and bacterial composition was stable across diatom growth phases (exponential versus stationary) and approximately 1 yr in culture. Among all cultures, bacterial communities differed significantly with Pseudo-nitzschia species and toxigenicity. Toxigenic strains of Pseudo-nitzschia hosted fewer bacterial ARISA operational taxonomic units (OTUs), in comparison to nontoxigenic strains. We constructed two 16S rDNA clone libraries to identify bacteria coexisting with 1 P. multiseries (toxigenic) and 1 P. delicatissima (nontoxigenic) culture. Both cultures hosted members of the Roseobacter clade, Gammaproteobacteria, and Flavobacteria, yet the specific bacteria coexisting with each Pseudo-nitzschia strain differed at the genus level or above. Our findings support the hypothesis that bacterial communities respond to DA or other species-specific differences in the environments created by Pseudo-nitzschia strains.
Marine Ecology Progress Series, 2004
The effect of elevated pH on growth and on production of the neurotoxin domoic acid was studied in selected diatoms belonging to the genera Pseudo-nitzschia and Nitzschia. Growth of most of the 11 species studied stopped at pH values of 8.7 to 9.1. However, for P. delicatissima and N. navis-varingica the pH limit for growth was higher, 9.3 and 9.7 to 9.8, respectively. A compilation of all available data on the pH limits for growth of marine planktonic diatoms suggests that species from ponds and rock pools all have higher limits than coastal and oceanic species. Taking only coastal and oceanic species into account, the data suggest that smaller species have a higher upper pH limit for growth than larger species. Elevated pH induced production of domoic acid in P. multiseries in amounts comparable to those detected previously under silicate and phosphate limitation. As Pseudo-nitzschia species are found in high concentrations in nutrient-enriched areas, high pH and hence induction of the production of domoic acid would be expected during blooms. These results may help to understand when and why Pseudo-nitzschia species produce domoic acid in the field.
Journal of Phycology, 1996
Production of domozc acid (DA), a neurotoxzn, by the din to vi Pseudon i t z sc h i a mu 1 ti se r i es ( p rev zo usly Nitzschia pungensf: multiseries) Hasle and zts cellular chernzcal composztion were studied in phosphate-lzmited cheinohtat contznuous cultures and in subseque?1t batch cultures. Under steaclj-state chelnostat condztzons, D A production increased frow 0 . 0 1 to 0.26 pg DA.cell-"d-' as the growth rate decreased. W h e n the nutrzent supply was discoutinuecl (to produce a batch culture), D A production was eiahanced bq a factor of ca 3. D A productzon was teniporarzlj suspended upon addztioil of phosphate to the batch cultures but resumed 1 d later at a hzgher rate coincident ulith the decline of phosphate uptake. I n both steadystate contznuous culture and batch culture, more D A was produced when alkaline phosphatase actzuzty (APA) urns high The associatzon of high DA production with high leilels of APi4 and high cellular N:P ratios strong11 suggests that phosphate liinitatzon enhances D A productzon. Also, DL4 production was hzgh when other przmary metabolism (e.g. uptake of carbon, nitrogen, phosphorus and szlicon, and cell d i m i o n ) was low, but chlorophyll a and adenoszne trzphosphate were general11 hzgh. Thzs suggests that the Jyntheszs of DA requires a substantial amount of bzogenzc energ).
Journal of Phycology, 2002
A nonaxenic isolate of the potentially toxic diatom Pseudo-nitzschia australis (Frenguelli) from Irish waters was tested in two separate batch culture experiments. When grown under a low irradiance ( ف 12 mol photons ؒ m Ϫ 2 ؒ s Ϫ 1 ; 16:8-h light:dark cycle) for up to 40 days, the culture produced only trace amounts of the neurotoxin domoic acid (DA) during late stationary phase. Growth at a higher irradiance ( ف 115 mol photons ؒ m Ϫ 2 ؒ s Ϫ 1 ; 12:12-h light:dark cycle) resulted in DA production starting during late exponential phase and reaching a maximum concentration of 26 pg DA ؒ cell Ϫ 1 during late stationary phase. Liquid chromatography coupled to mass spectrometry was used to confirm the identity of DA in the culture. Irradiance and photoperiod could be important factors that contribute directly or indirectly to the control of DA production in P. australis. This is the first record of a DA-producing diatom in Irish waters, and results indicate P. australis may have been the source of DA that has recently contaminated shellfisheries in this area.
2010
Twenty-six Pseudo-nitzschia multistriata cultures were tested for intracellular domoic acid production and fourteen were found to be toxic. Four suboptimal growth conditions were compared with conditions observed to be optimal to explore possible triggers for intracellular domoic acid production. Silica-and phosphate-limitation and low light treatment induced elevated toxin concentrations whereas high temperature appeared to suppress it. Inheritance of the toxin-production ability was investigated by measuring intracellular toxin content in a total of thirty-nine F 1 strains from two different crosses. Results showed radical differences in domoic acid levels among the F 1 offspring from the same parents.