CALCIUM IS REQUIRED FOR SWIMMING BY THE NONFLAGELLATED CYANOBACTERIUMSYNECHOCOCCUS STRAIN WH8113

The marine cyanobacterium Synechococcus strain WH8113 swims in the abs ence of any recognizable organelles of locomotion, We have found that calcium is required for this motility, Cells deprived of calcium stopp ed swimming, while addition of calcium completely restored motility, N o other divalent ions tested could replace calcium, Terbium, a lanthan ide ion, blocked motility even when calcium was present at 10(5)-fold- higher concentrations, presumably by occupying calcium binding sites, Calcium chelators, EGTA or EDTA, blocked motility, even when calcium w as present at 25-fold-higher concentrations, presumably by acting as c alcium ionophores. Finally, motility was blocked by verapamil and nitr endipine, molecules known to block voltage-gated calcium channels of e ukaryotic cells by an allosteric mechanism, These results suggest that a calcium potential is involved in the mechanism of motility.