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Effect of thorium on the growth and capsule morphology of Bradyrhizobium
Author(s) -
Santamaría Mónica,
DíazMarrero Ana R.,
Hernández Jairo,
GutiérrezNavarro Angel M.,
Corzo Javier
Publication year - 2003
Publication title -
environmental microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.954
H-Index - 188
eISSN - 1462-2920
pISSN - 1462-2912
DOI - 10.1046/j.1462-2920.2003.00487.x
Subject(s) - biology , bradyrhizobium , precipitation , bacteria , microbiology and biotechnology , morphology (biology) , nuclear chemistry , suspension (topology) , thorium , amorphous solid , bradyrhizobium japonicum , rhizobiaceae , rhizobium , chemistry , materials science , symbiosis , crystallography , metallurgy , physics , mathematics , uranium , homotopy , meteorology , pure mathematics , genetics
Summary The thorium effect on Bradyrhizobium growth was assayed in liquid media. Th 4+ inhibited the growth of Bradyrhizobium ( Chamaecytisus ) BGA‐1, but this effect decreased in the presence of suspensions of live or dead bacterial cells. Th 4+ induced the formation of a gel‐like precipitate when added to a dense suspension of B. ( Chamaecytisus ) BGA‐1 cells. Viable Bradyrhizobium cells remained in suspension after precipitate formation. Thorium was recovered in the precipitate, in which polysaccharide, lipopolysaccharide and proteins were also found. After Th 4+ addition, the morphology of B. ( Chamaecytisus ) BGA‐1 or Bradyrhizobium japonicum USDA 110 sedimented cells studied by scanning electron microscopy changed from an entangled network of capsulated bacteria to uncapsulated individual cells and an amorphous precipitate. Energy‐dispersive X‐ray spectroscopy showed that thorium was mainly in the amorphous fraction. Precipitate was also formed between B. ( Chamaecytisus ) BGA‐1 and Al 3+ , which was also toxic to this bacterium. Precipitate induced by Th 4+ or Al 3+ was found in all Bradyrhizobium and Sinorhizobium strains tested, but not in Rhizobium , Salmonella typhimurium , Aerobacter aerogenes or Escherichia coli . These results suggest a specific defence mechanism based on metal precipitation by extracellular polymers.