Green algal extracellular products regulate antialgal toxin production in a cyanobacterium.
Many bacterial genes and virulence factors are regulated by interbacterial and/or host-parasite chemical signals. We demonstrate that toxin production by a free-living freshwater cyanobacterium is regulated in part by the presence of extracellular products of a eukaryotic green alga. In growth experiments, extracellular products made by the cyanobacterium Anabaena flos-aquae contained both anatoxin and microcystin, and significantly reduced the yield of Chlamydomonas reinhardtii, a green alga. Based on experiments in which we added purified toxins to C. reinhardtii cultures, we believe that microcystin was responsible for the growth reduction. A. flos-aquae produced anatoxin constitutively when grown alone, but anatoxin concentration increased in the presence of C. reinhardtii elicitors. Microcystin accumulation depended on the growth phase; however, high concentrations of C. reinhardtii extracellular products completely inhibited microcystin accumulation. Our results demonstrate that cyanobacterial toxin production may be regulated by complex growth phase-dependent and environmental chemical cues, and suggest that secreted chemicals can mediate the outcome of competition between the cyanobacterium A. flos-aquae and the green alga C. reinhardtii.
Kearns
K D
KD
Institute of Ecology, University of Georgia, Athens 30602-2202, USA. kdkearns@sparc.ecology.uga.edu
Hunter
M D
MD
D017033:Anabaena / Q000254:growth & development / Q000378:metabolism*; D000818:Animals; D001427:Bacterial Toxins / Q000096:biosynthesis*; D002450:Cell Communication; D016825:Chlamydomonas reinhardtii / Q000166:cytology / Q000187:drug effects / Q000254:growth & development* / Q000378:metabolism*; D000087522:Cyanobacteria Toxins; D005110:Extracellular Space / Q000378:metabolism; D008387:Marine Toxins / Q000096:biosynthesis*; D052998:Microcystins; D010456:Peptides, Cyclic / Q000096:biosynthesis* / Q000494:pharmacology
D001427:Bacterial Toxins; D000087522:Cyanobacteria Toxins; D008387:Marine Toxins; D052998:Microcystins; D010456:Peptides, Cyclic; C078588:microcystin