Titanospirillum velox: A huge, speedy, sulfur-storing spirillum from Ebro Delta microbial mats

摘要

A long (20-30 #mu#), wide (3-5 #mu#m) micro- bial-mat bacterium from the Ebro Delta (Tarragona, Spain) was grown in mixed culture and videographcd live. Intra- cellular elemental sulfur globules and unique cell termini were observed in scanning-electron-microprobe and trans- mission-electron micrographs. A polar organelle underlies bundles of greater than 60 flagella at each indented termi- nus. These Gram-negative bacteria bend, flex, and swim in a spiral fashion; they translate at speeds greater than 10 body lengths per second. The large size of the spirillum permits direct observation of cell motility in single individ- ual bacteria. After desiccation (i.e., absence of standing water for at least 24 h), large populations developed in mat samples remoistened with sea water. Ultrastructural obser- vations reveal abundant large sulfur globules irregularly distributed in the cytoplasm. A multilayered cell wall, pliable and elastic yet rigid, distends around the sulfur globules. Details of the wall, multiflagellated termini, and large cytoplasmic sulfur globules indicate that these fast- moving spirilla are distinctive enough to warrant a genus and species designation: Titanospirillum velox genus nov., sp. nov. The same collection techuiques at a similar habitat in the United States (PIum lsland, northeast Essex County, Massachusetts) also yielded large populations of the bac- terium among purple phototrophic and other inhabitants of sulfurous microbial-mat muds. The months-long survival of T.velox from Spain and from the United States in closed jars filled with mud taken fro