Molecular quantification of toxic Alexandrium fundyense in the Gulf of Maine.

Abstract

ing genes in T. erythraeum. Given the morphological distinction of the Trichodesmium species, this high degree of similarity was surprising. However, coverage of the entire gene in each species may reveal regions within the genes that are less highly conserved. This hypothesis is consistent with the results for the only other functional gene to be sequenced from multiple Trichodesmium species, hetR, which shows a lower degree of similarity, 91%–95% (7). Despite extensive efforts to amplify all the genes by varying annealing temperature, primers, and concentrations of magnesium, enzyme, and template, we were unable to amplify pstS2 or phoA from T. thiebautii. This is particularly interesting because T. thiebautii has been shown to have alkaline phosphatase activity (2), and because of the degree of similarity of phoA among the other species. Additionally, T. thiebautii’s evolutionary relationship, inferred from Trichodesmium ITS sequences (6), indicates T. tenue and K. spiralis are more closely related to each other than to T. thiebautii. It may be that phoA in T. thiebautii is very different compared to the other species or that a different gene and gene product are used in the hydrolysis of dissolved organic phosphorus for this species. Future work is needed to determine whether pstS2 and phoA are present in T. thiebautii. Although other species and isolates of Trichodesmium should be analyzed, our initial identification of putative P-regulated genes in these Trichodesmium species has improved our knowledge of phosphorus scavenging mechanisms in this important genus. This work was funded by NSF grant OCE-0220945, and by NSF Research Experience for Undergraduates grant OCE-0097498.