Influence of microbial interactions on the susceptibility of Karenia spp. to algicidal bacteria

Abstract

A bacterial strain (D38BY) belonging to the family Flavobacteriaceae and antagonistic towards an algicidal bacterium (strain S03; Flavobacteriaceae) was isolated from a culture of the red tide dinoflagellate Karenia brevis that had previously been characterized as resistant to attack by strain S03. This antagonistic bacterium increased the survival time of otherwise susceptible, bacteriafree K. brevis cultures in a concentration-dependent manner during exposure to the algicidal bacterium. Experimental evidence indicated that direct contact was required in order for strain D38BY to inhibit the killing activity of algicidal strain S03. While further work is needed to determine its precise mode of action, the antagonistic properties of strain D38BY provide further evidence that the resistance or susceptibility of certain algal taxa to algicidal attack can be more a function of interactions within the ambient microbial community than an intrinsic property of the alga. KEY WORDS: Algicidal bacteria · Antagonism · CFB complex · Karenia brevis · Microbial interactions Resale or republication not permitted without written consent of the publisherAquat Microb Ecol 50: [251][252][253][254][255][256][257][258][259] 2008 Previous studies have shown that bacteria in contact with organic matter have a greater tendency to inhibit the growth of other bacteria (Nair & Simidu 1987, Burgess et al. 1999. Long & Azam (2001) reported that the number of bacterial strains inhibited by attached bacteria was approximately 3 times higher than those adversely affected by free-living bacteria. Grossart et al. (2004) found that over 50% of strains isolated from marine aggregates were capable of inhibiting at least 1 other bacterium. Although these studies highlight the contributions of attached bacteria, free-living microbes also warrant consideration. Mayali & Doucette (2002) showed that resistance and susceptibility to an algicidal bacterium could be transferred among cultures of the red tide dinoflagellate Karenia brevis simply by exchanging the native freeliving microbial communities associated with susceptible and resistant isolates. Their findings implicated interactions among bacteria as a potential mechanism for modulating the killing activity of algicidal strains. The ecological significance of antagonistic or inhibitory interactions between bacteria remains largely speculative. Nonetheless, such interactions could influence competition for nutrients or space (Holmström & Kjelleberg 1999) and lead to changes in microbial species composition that may, in turn, alter the nature and rates of bacterially-mediated carbon cycling (Martinez et al. 1996, Long et al. 2003. A better understanding of these relationships and knowledge of the key species involved are essential for predicting their impacts on marine ecosystems. Our goal was to isolate and characterize the antagonistic microbial component(s) of a Karenia brevis culture responsible for impeding the killing activity of an algicidal bacterium reported as lethal to other ...

Variability of Prokaryotic Community Structure in a Drinking Water Reservoir (Marathonas, Greece)

“…Cytophaga -like bacteria have been found in Lake Constance, the Mindelsee and the Meldsee (SW Germany) (48). Both Cytophagales and Flavobacteriales have been associated with harmful algal blooms (49) based on their algicidal activity and antagonism towards other bacteria (51). Within the order of Sphingobacteriales , one doubleton was affiliated with Candidatus ‘ Aquirestis calciphila ’.…”

Investigation of the algicidal exudate produced by Shewanella sp. IRI-160 and its effect on dinoflagellates

“…Several studies, for instance, have described algicidal bacteria that are only effective on a specific genus or species of algae (Fukami et al, 1992;Doucette et al, 1999), while others target a broader range of algal classes (Imai et al, 1995;Lovejoy et al, 1998;Kang et al, 2008;Roth et al, 2008a). The mode of activity can also vary such that direct cell-to-cell contact is necessary for algicidal activity in some bacterial species (Kim et al, 1998;Roth, 2005;Roth et al, 2007Roth et al, , 2008b, while other algicidal bacteria have been found to secrete bioactive compounds with varying effects on the target algal species (Lovejoy et al, 1998;Doucette et al, 1999;Lee et al, 2000;Skerratt et al, 2002;Kang et al, 2008;Kim et al, 2008;Mayali et al, 2008). For example, Roth et al (2007) found that direct contact with the dinoflagellate Karenia brevis was required for algicidal activity of Flavobacteriaceae strain S03, which induced cell lysis after 24 h exposure.…”

Comparative analysis of bacterioplankton assemblages from Karenia brevis bloom and nonbloom water on the west Florida shelf (Gulf of Mexico, USA) using 16S rRNA gene clone libraries

“…In the specific case of K. brevis , the most comprehensive study of the associated microbial community was conducted almost two decades ago using classical bacteriological methods (Buck & Pierce, 1989). Since then, investigators have used molecular techniques to classify and characterize algicidal bacteria active against this dinoflagellate (Doucette et al , 1999; Mayali & Doucette, 2002; Roth et al , 2008a, b) and have documented a complex relationship between algicidal bacteria and antagonistic (against the algicidal bacteria), potentially co‐occurring microorganisms (Roth et al , 2008a). Moreover, the isolation of algicidal bacteria from waters with and without detectable K. brevis cells suggests that such strains are part of the ambient microbial community and likely increase in abundance when exposed to their target algal cells.…”