Inorganic and Metal-Organic Growth Requirements of the Genus Bacteroides1

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The inorganic and metal-organic growth requirements of ruminal and nonruminal Bacteroides species were compared. The heme requirement of many nonruminal Bacteroides species was similar to that of Bacteroides ruminicola subsp. ruminicola and was a general tetrapyrrole requirement. Some nonruminal Bacteroides species utilized succinate or alpha-ketoglutarate, as well as tetrapyrrole-containing compounds, in place of heme. Fe+ as well as heme was required for maximal yields of some Bacteroides species. The divalent cation requirements of Bacteroides species are complex. Mg2+ deletion from a medium containing Mg2+, Ca2+, Co2+, and Mn2+ reduced the yields of all isolates. Ca2+ deletion from the same medium reduced the growth yields of Bacteroides fragilis, B. fundiliformis, and one strain of B. oralis. The effects of Mg2+ and Ca2+ on the growth of Bacteroides isolates was influenced by other divalent cations. Relatively large quantities of Na+ were obligately required by all of the currently recognized predominant rumen Bacteroides species. Nonruminal Bacteroides species either did not require Na+ or required only small amounts. The Na+ requirement of some nonruminal Bacteroides species could be partially replaced by Li+ or Cs+. The Na+ requirement of rumen Bacteroides species was absolute. The inorganic and metal-organic growth requirements of Bacteroides species appear useful as aids in species differentiation.

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