Interactions of the Algicidal Bacterium Kordia algicida with Diatoms: Regulated Protease Excretion for Specific Algal Lysis

Abstract

Interactions of planktonic bacteria with primary producers such as diatoms have great impact on plankton population dynamics. Several studies described the detrimental effect of certain bacteria on diatoms but the biochemical nature and the regulation mechanism involved in the production of the active compounds remained often elusive. Here, we investigated the interactions of the algicidal bacterium Kordia algicida with the marine diatoms Skeletonema costatum, Thalassiosira weissflogii, Phaeodactylum tricornutum, and Chaetoceros didymus. Algicidal activity was only observed towards the first three of the tested diatom species while C. didymus proved to be not susceptible. The cell free filtrate and the >30 kDa fraction of stationary K. algicida cultures is fully active, suggesting a secreted algicidal principle. The active supernatant from bacterial cultures exhibited high protease activity and inhibition experiments proved that these enzymes are involved in the observed algicidal action of the bacteria. Protease mediated interactions are not controlled by the presence of the alga but dependent on the cell density of the K. algicida culture. We show that protease release is triggered by cell free bacterial filtrates suggesting a quorum sensing dependent excretion mechanism of the algicidal protein. The K. algicida / algae interactions in the plankton are thus host specific and under the control of previously unidentified factors.

Ubiquitous marine bacterium inhibits diatom cell division

“…These results suggest that C. atlanticus does not constitutively release a growth inhibitor into MB under these conditions, at least at an effective concentration. By contrast, another study showed that the flavobacterium Kordia algicida constitutively secretes a protease that negatively impacts several diatoms (Paul and Pohnert, 2011). One diatom, Chaetoceros didymus, appears to deactivate the algicidal activity of K. algicida through production of its own counter-acting protease-degrading enzymes (Paul and Pohnert, 2013).…”

“…Beneficial bacteria typically provide a useful service to the diatom in exchange for organic nutrients; for example, Ruegeria pomeroyi provides vitamin B 12 to Thalassiosira pseudonana in exchange for the organic sulfur compound 2,3-dihydroxypropane-1-sulfonate . Many detrimental bacteria are from the phylum Bacteroidetes or the class Gammaproteobacteria (Mayali and Azam, 2004) and are thought to harm phytoplankton by secreting proteases or other algaecides (Lee et al, 2000;Paul and Pohnert, 2011;Seyedsayamdost et al, 2011).…”

Laboratory-Cultured Strains of the Sea Anemone Exaiptasia Reveal Distinct Bacterial Communities

“…or Pseudomonas veronii, present in H2 and CC7, respectively. Kordia is an algicidal bacterium (Sohn et al, 2004) capable of inhibiting the growth of diatoms, and even killing them by active lysis (Paul and Pohnert, 2011). Its ubiquity and high abundance (37%) in the H2 core microbiome indicates that these bacteria might be important for the host; however, this has to be studied in more depth.…”

Perspectives on the microbial carbon pump with special reference to microbial respiration and ecosystem efficiency in large estuarine systems

“…AHLs have also been identified in marine surface-associated microbial communities (Decho et al, 2009;Huang et al, 2009). The bacterium Kordia algicida relies on QS-dependent excretion of an algicidal protein to suppress activity of marine diatoms such as Skeletonema costatum, Thalassiosira weissflogii and Phaeodactylum tricornutum (Paul and Pohnert, 2011). Algicidal bacteria, such as K. algicida, may contribute not only to the termination of algal blooms, but also to the release of algal particulate organic carbon (POC) and DOC, thus influencing the MCP process.…”