title: Sodium, an obligate growth requirement for predominant rumen bacteria.
abstract: Sodium is an obligate growth requirement for most currently recognized predominant species of rumen bacteria. The isoosmotic deletion of Na(+) from a nutritionally adequate defined medium completely eliminated growth of most species. Growth yields and rates were both a function of Na(+) concentration for Na(+)-requiring species, and Na(+) could not be replaced by Rb(+), Li(+), or Cs(+) when these ions were substituted for Na(+) at a concentration equivalent to an Na(+) concentration that supported abundant growth. Li(+), Cs(+), or Rb(+) was toxic at an Na(+)-replacing concentration (15 mM) but not at a K(+)-replacing concentration (0.65 mM). K(+) was also an obligate growth requirement for rumen bacteria in media containing Na(+) and K(+) as major monovalent cations, but K(+) could be replaced, for most species, by Rb(+). The quantities of Na(+) that support rapid and abundant growth of Na(+)-requiring rumen bacteria show that these organisms are slight halophiles. A growth requirement for Na(+) appears more frequent among nonmarine bacteria than has been previously believed.
mesh_terms: D000693:Anaerobiosis; D000818:Animals; D001419:Bacteria / Q000254:growth & development / Q000378:metabolism; D002586:Cesium / Q000378:metabolism; D003470:Culture Media; D005750:Gastric Juice; D008094:Lithium / Q000378:metabolism; D011188:Potassium / Q000378:metabolism; D012413:Rubidium / Q000378:metabolism; D012417:Rumen / Q000382:microbiology*; D012964:Sodium / Q000378:metabolism*; D013045:Species Specificity; D013053:Spectrophotometry
chemical_list: D003470:Culture Media; D002586:Cesium; D008094:Lithium; D012964:Sodium; D012413:Rubidium; D011188:Potassium