Potassium uptake and retention by Oceanomonas baumannii at low water activity in the presence of phenol

Abstract

Oceanomonas baumanniiT (ATCC 700832) is a halotolerant bacterium capable of degrading phenol, which requires potassium in order for turgor growth to occur in minimal medium containing 5% NaCl (w/v). However, at this salinity growth can be inhibited by reduced potassium concentrations. The affinity for potassium (K S ) was determined to be 219 WM and 408 WM for cultures utilising phenol and succinate respectively as the sole carbon source for growth. Rubidium but not caesium could substitute for potassium in alleviating growth inhibition due to potassium limitation. The effect of elevated phenol on potassium retention was studied, and it was shown that contrary to expectations, as external phenol concentration was increased the levels of intracellular potassium were significantly elevated. This observation correlated with changes in the cytoplasmic membrane, particularly the increase in the saturated:unsaturated fatty acid ratio from 0.47 to 1.44, and the decrease in the zwitterionic:anionic phospholipid ratio from 2.23 to 1.22. Both these changes promote membrane bilayer configurations and increase lipid ordering of the membrane reducing its permeability and inhibiting cation efflux. ß

Cesium (137Cs and 133Cs), Potassium and Rubidium in Macromycete Fungi and Sphagnum Plants

“…Although correlation analyses is not the best tool for analyzing the uptake mechanism, the closest positive correlations between K:Rb ratios in fungal mycelium and in soil indicated similarities in the uptake mechanism of these two elements by fungi, although the relationships between K: 133 Cs ratios in soil mycelium and in soil were less pronounced. These findings were in good agreement with the suggestion by Yoshida & Muramatsu (1998) that there might be an alternative pathway for 133 Cs uptake into cells and the mechanism of 133 Cs uptake by fungi could be similar to that for Rb, as 133 Cs does not show a good correlation with K. The high efficiency of Rb uptake by fungi indicates Rb, but not 133 Cs, eventually replaces essential K due to K limitation (Brown & Cummings, 2001) and Rb has the capacity to partially replace K, but 133 Cs does not (Wallace, 1970 and references therein). Forest plants apparently discriminate between K+ and Rb+ in soils and a shortage of K+ favors the uptake of the closely related Rb+ ion (Nyholm & Tyler, 2000), whereas, increasing K+ availability in the system decreases Rb+ uptake (Drobner & Tyler, 1998).…”

Microbial Genomics and the Periodic Table

“…A major impetus for the study of these elements has been the microbiological sequestration of radionuclides produced in nuclear reactors, such as cesium-137 (4,117,130 Rubidium and barium are not of concern as radioactive pollutants, but the ability of these elements to function as analogs to the lighter essential elements of their respective groups (or ions of similar valence) has been explored. No absolute requirement for rubidium in bacterial growth has been identified, but in the absence of K ϩ , Rb ϩ restored normal or near-normal growth in several bacteria (17,53,77). Rb ϩ effectively substituted for K ϩ in the biosynthesis of a bacterial pigment (18) and for K ϩ or NH 4 ϩ in the activation of some bacterial and fungal enzymes (11,135,141).…”

Complete Genome Sequence of Oceanimonas sp. GK1, a Halotolerant Bacterium from Gavkhouni Wetland in Iran

“…Two unique genes, trkA and trkH, were predicted in the GK1 genome, and these encode TrkA and TrkH proteins as two components of Trk system for potassium uptake in response to osmotic stress (3,7). The choline and betaine uptake and betaine biosynthesis system was identified in the genome.…”