This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Reprints and Permissions Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Ballal, A. Articles by Apte, S. K. Search for Related Content PubMed PubMed Citation Articles by Ballal, A. Articles by Apte, S. K. Agricola Articles by Ballal, A. Articles by Apte, S. K.

 Previous Article  |  Next Article 

Applied and Environmental Microbiology, September 2005, p. 5297-5303, Vol. 71, No. 9
0099-2240/05/$08.00+0     doi:10.1128/AEM.71.9.5297-5303.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.

Differential Expression of the Two kdp Operons in the Nitrogen-Fixing Cyanobacterium Anabaena sp. Strain L-31

Molecular Biology Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085, India

Received 22 February 2005/ Accepted 19 April 2005

In several types of bacteria, the Kdp ATPase (comprising of the KdpABC complex) is an inducible, high-affinity potassium transporter that scavenges K⁺ from the environment. The cyanobacterium Anabaena sp. strain L-31 showed the presence of not one but two distinct kdp operons in its genome. The kdp1 consisted of kdpA1B1G1C1D genes, whereas the kdp2 contained the kdpA2B2G2C2 genes. Among the regulatory genes, the kdpD open reading frame of Anabaena sp. strain L-31 was truncated compared to the kdpD of other bacteria, whereas a kdpE-like gene was absent in the vicinity of the two kdp operons. In response to K⁺ limitation (<0.05 mM external K⁺), only kdp2 (and not kdp1) expression could be detected as a 5.3-kb transcript on Northern blots, indicating that kdpA2B2G2C2 genes constitute a polycystronic operon. Unlike E. coli, addition of osmolytes like NaCl, or a change in pH of the medium did not enhance the kdp expression in Anabaena sp. strain L-31. Interestingly, the Anabaena sp. strain L-31 kdp2 operon was strongly induced in response to desiccation stress. The addition of K⁺ to K⁺-starved cultures resulted in repression and degradation of kdp2 transcripts. Our results clearly show that kdp2 is the major kdp operon expressed in Anabaena sp. strain L-31 and may play an important role in adaptation to K⁺ limitation and desiccation stress.