Nitrogen utilization and metabolism in ruminococcus albus 8

Jong Nam Kim, Emily De Crescenzo Henriksen, Isaac K.O. Cann, Roderick I. Mackie

Research output: Contribution to journalArticle

Abstract

The model rumen Firmicutes organism Ruminococcus albus 8 was grown using ammonia, urea, or peptides as the sole nitrogen source; growth was not observed with amino acids as the sole nitrogen source. Growth of R. albus 8 on ammonia and urea showed the same growth rate (0.08 h-1) and similar maximum cell densities (for ammonia, the optical density at 600 nm [OD600] was 1.01; and for urea, the OD600 was 0.99); however, growth on peptides resulted in a nearly identical growth rate (0.09 h-1) and a lower maximum cell density (OD600=0.58). To identify differences in gene expression and enzyme activities, the transcript abundances of 10 different genes involved in nitrogen metabolism and specific enzyme activities were analyzed by harvesting mRNA and crude protein from cells at the mid- and late exponential phases of growth on the different N sources. Transcript abundances and enzyme activities varied according to nitrogen source, ammonia concentration, and growth phase. Growth of R. albus 8 on ammonia and urea was similar, with the only observed difference being an increase in urease transcript abundance and enzyme activity in urea-grown cultures. Growth of R. albus 8 on peptides showed a different nitrogen metabolism pattern, with higher gene transcript abundance levels of gdhA, glnA, gltB, amtB, glnK, and ureC, as well as higher activities of glutamate dehydrogenase and urease. These results demonstrate that ammonia, urea, and peptides can all serve as nitrogen sources for R. albus and that nitrogen metabolism genes and enzyme activities of R. albus 8 are regulated by nitrogen source and the level of ammonia in the growth medium.

Original languageEnglish (US)
Pages (from-to)3095-3102
Number of pages8
JournalApplied and environmental microbiology
Volume80
Issue number10
DOIs
StatePublished - May 2014

ASJC Scopus subject areas

  • Biotechnology
  • Food Science
  • Applied Microbiology and Biotechnology
  • Ecology

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