Identification of bacteria associated with Dinoflagellates (Dinophyceae) Alexandrium spp. using tyramide signal amplification fluorescent in situ hybridization and confocal microscopy

In the marine environment, phytoplankton and bacterioplankton can be physically associated. Such association has recently been hypothesized to be involved in the toxicity of the dinoflagellate genus Alexandrium. However, the methods, which have been used so far to identify, localize, and quantify bacteria associated with phytoplankton, are either destructive, time consuming, or lack precision. In the present study we combined tyramide signal amplification–fluorescent in situ hybridization (TSA-FISH) with confocal microscopy to determine the physical association of dinoflagellate cells with bacteria. Dinoflagellate attached microflora was successfully identified with TSA-FISH, whereas FISH using monolabeled probes failed to detect bacteria, because of the dinoflagellate autofluorescence. Bacteria attached to entire dinoflagellates were further localized and distinguished from those attached to empty theca, by using calcofluor and DAPI, two fluorochromes that stain dinoflagellate theca and DNA, respectively. The contribution of specific bacterial taxa of attached microflora was assessed by double hybridization. Endocytoplasmic and endonuclear bacteria were successfully identified in the nonthecate dinoflagellate Gyrodinium instriatum. In contrast, intracellular bacteria were not observed in either toxic or nontoxic strains of Alexandrium spp. Finally, the method was successfully tested on natural phytoplankton assemblages, suggesting that this combination of techniques could prove a useful tool for the simultaneous identification, localization, and quantification of bacteria physically associated with dinoflagellates and more generally with phytoplankton.

A study of Aldred's multiple glosses to the Lindisfarne Gospels

Aldred, the glossator of the Lindisfarne Gospels, presents himself as carefully rendering the Latin lemmata in front of him, in terms of both their internal structure and meaning. His work includes a very high number of multiple glosses, which often attempt to clarify the polysemous character of a lemma or to provide additional information. This paper explores the multiple glosses including different lexemes which Aldred added to lexical lemmata in Mark’s Gospel in an attempt to establish whether there is any correlation between Aldred’s ordering practices and the frequency with which he used the interpretamenta to render those lemmata. The results of the study show some preference for placing the interpretamentum which most commonly renders the Latin lemma in first position, although Aldred’s practice is not fully consistent.