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Rhodobacter sphaeroides only showed chemotaxis towards ammonia if grown under nitrogen-limited conditions. This chemotactic response was completely inhibited by the addition of methionine sulfoximine. There was no effect of methionine sulfoximine treatment on motility or taxis towards propionate, demonstrating that the effect is specific to ammonia taxis. It is known that methionine sulfoximine inhibits glutamine synthetase and hence blocks ammonia assimilation. Methionine sulfoximine does not inhibit ammonia transport in R. sphaeroides; therefore, these results suggest that limited metabolism via a specific pathway is required subsequent to transport to elicit a chemotactic response to ammonia. Bacteria grown on high ammonia show transport but no chemotactic response to ammonia, suggesting that the pathway of assimilation is important in eliciting a chemotactic response.

Original publication




Journal article


J Bacteriol

Publication Date





2900 - 2902


Ammonia, Chemotaxis, Methionine Sulfoximine, Propionates, Rhodobacter sphaeroides