Open AccessCaesium transport in the cyanobacterium Anabaena variabilis : Kinetics and evidence for uptake via ammonium transport system(s)
Author(s) -
Avery Simon V.,
Codd Geoffrey A.,
Gadd Geoffrey M.
Publication year - 1992
Publication title -
fems microbiology letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.899
H-Index - 151
eISSN - 1574-6968
pISSN - 0378-1097
DOI - 10.1111/j.1574-6968.1992.tb05375.x
Subject(s) - anabaena variabilis , ammonium , chemistry , kinetics , nitrogen , ammonium chloride , anabaena , biophysics , nuclear chemistry , biology , cyanobacteria , bacteria , genetics , physics , organic chemistry , quantum mechanics
Analysis of caesium uptake over a range of external Cs + concentrations revealed that uptake was determined by a single transport system [ K m approx. 0.25 mM; V max approx. 220 nmol Cs + h −1 (10 9 cells) −1 ] in the cyanobacterium Anabaena variabilis . Linear inhibition of Cs + uptake in the presence of elevated external concentrations of NH 4 + (added as chloride) resulted in an increase in the K m and a decrease in the V max suggesting that NH 4 + was a competitive/non‐competitive inhibitor of Cs + uptake. Cs + uptake was markedly dependent on the nitrogen source supplied during growth of A. variabilis ; maximal uptake was observed in nitrogen‐fixing cells. Lowest levels of Cs + uptake were observed in a mutant strain of A. variabilis which was deficient in NH 4 + transport. These results suggest that Cs + and NH 4 + share a common transport mechanism in A. variabilis .