Identification and Characterization of Potentially Algal‐lytic Marine Bacteria Strongly Associated with the Toxic Dinoflagellate Alexandrium catenella

Abstract

The toxic dinoflagellate Alexandrium catenella isolated from fjords in Southern Chile produces several analogues of saxitoxin and has been associated with outbreaks of paralytic shellfish poisoning. Three bacterial strains, which remained in close association with this dinoflagellate in culture, were isolated by inoculating the dinoflagellate onto marine agar. The phenotypically different cultivable bacterial colonies were purified. Their genetic identification was done by polymerase chain reaction amplification of the 16S rRNA genes. Partial sequence analysis suggested that the most probable affiliations were to two bacterial phyla: Proteobacteria and the Cytophaga group. The molecular identification was complemented by morphological data and biochemical profiling. The three bacterial species, when grown separately from phytoplankton cells in high-nutrient media, released algal-lytic compounds together with aminopeptidase, lipase, glucosaminidase, and alkaline phosphatase. When the same bacteria, free of organic nutrients, were added back to the algal culture they displayed no detrimental effects on the dinoflagellate cells and recovered their symbiotic characteristics. This observation is consistent with phylogenetic analysis that reveals that these bacteria correspond to species distinct from other bacterial strains previously classified as algicidal bacteria. Thus, bacterial-derived lytic activities are expressed only in the presence of high-nutrient culture media and it is likely that in situ environmental conditions may modulate their expression.

Characterizing the Interactions Among a Dinoflagellate, Flagellate and Bacteria in the Phycosphere of Alexandrium tamarense (Dinophyta)

“…Many of the α-and γ-Proteobacteria have been shown to be the phycosphere bacteria of A. tamarense (Mayali and Azam, 2004;Bai et al, 2011). The Pseudomonas, alteromonas, Pseudoalteromonas, and Roseobacter group, which show a high identity to our isolations, were well known to be key algicidal bacteria of A. tamarense and many other harmful algae (Lovejoy et al, 1998;Mayali and Azam, 2004;Amaro et al, 2005;Wang et al, 2010;Oh et al, 2011), and this finding suggests that bacteria might be useful for regulating HABs.…”

“…Algal-bacterial interactions are a typical model in microecosystem studies (Doucette et al, 1998;Amaro et al, 2005), in part because bacteria transform energy and regenerate inorganic nutrient in marine ecosystems (Azam et al, 1983;Su et al, 2011). Alexandrium tamarense is a model dinoflagellate alga that is globally distributed and known for producing harmful algal blooms (HABs) that cause paralytic shellfish poisoning (Anderson et al, 1996).…”

Allelopathic potential of the dinoflagellate Alexandrium tamarense on marine microbial communities

“…Bacteria associated with diatom cultures revealed specific bacterial ''satellite'' communities (Schä fer et al, 2002;Grossart et al, 2005;Kaczmarska et al, 2005). In Alexandrium cultures, the presence of specific bacterial consortia may be explained by symbiotic relationships between bacteria and the dinoflagellate (Amaro et al, 2005;Jasti et al, 2005). Additionally, cell wall components, exudates, pigment composition and life cycle features of the algae may also select for specific bacterial consortia.…”

Effects of bacterial communities on biofuel-producing microalgae: stimulation, inhibition and harvesting

“…and Thalassobius aestuarii were key factors that caused the lysis (Wang et al, 2010c). Many bacterial isolates have been proved to have the capability to kill microalgae (algicidal activity) by different ways (Amaro et al, 2005;Lovejoy et al, 1998;Simon et al, 2002;Skerratt et al, 2002). Certain algicidal bacterial strains (e.g.…”