Sodium-coupled energy transduction in the newly isolated thermoalkaliphilic strain LBS3

Abstract

Strain LBS3 is a novel anaerobic thermoalkaliphilic bacterium that grows optimally at pH 9.5 and 50؇C. Since a high concentration of Na ؉ ions is required for growth, we have analyzed the primary bioenergetic mechanism of energy transduction in this organism. For this purpose, a method was devised for the isolation of right-side-out membrane vesicles that are functional for the energy-dependent uptake of solutes. A strict requirement for Na ؉ was observed for the uptake of several amino acids, and in the case of L-leucine, it was concluded that amino acid uptake occurs in symport with Na ؉ ions. Further characterization of the leucine transport system revealed that its pH and temperature optima closely match the conditions that support the growth of strain LBS3. The ATPase activity associated with inside-out membrane vesicles was found to be stimulated by both Na ؉ and Li ؉ ions. These data suggest that the primary mechanism of energy transduction in the anaerobic thermoalkaliphilic strain LBS3 is dependent on sodium cycling. The implications of this finding for the mechanism of intracellular pH regulation are discussed.

Anaerobranca gottschalkii sp. nov., a novel thermoalkaliphilic bacterium that grows anaerobically at high pH and temperature.

“…The function of this ion in neutrophiles (Lolkema et al, 1994), as well as alkaliphiles (Krulwich & Guffanti, 1989 ;Krulwich et al, 1990) and some extremophiles (Speelmans et al, 1995), is either as a coupling ion for energy transduction or in pH homeostasis. We have demonstrated previously that Na + ions play a crucial role in the energy transduction of strain LBS3 T (Prowe et al, 1996). This was also supported by the fact that Na + could not be replaced by K + in the growth medium.…”

“…3c). As reported previously, Na + ions play a major role in the energy transduction of this micro-organism ; K + ions have no such effect (Prowe et al, 1996). Based on these results, it can be concluded that A. gottschalkii LBS3 T depends strictly on Na + ions for growth.…”

“…A. gottschalkii LBS3 T is, nevertheless, regarded as Gram-positive, due to the data obtained from 16S rDNA analysis (see below). This was also supported by the fact that protoplasts were obtained easily by lysozyme treatment (Prowe et al, 1996). Ultrathin sectioning of cells also showed an atypical thin cell wall (Fig.…”

“…In this report, we describe the isolation, characterization and identification of a new anaerobic thermoalkaliphile, LBS3 T , isolated from a hot alkaline inlet from the alkaline Lake Bogoria, Kenya. Previously, we reported on the role of sodium ions in the process of energy transduction in this extremophile (Prowe et al, 1996).…”

Ferrous-iron-dependent Uptake ofL-Glutamate by a Mesophilic, Mixotrophic Iron-oxidizing Bacterium Strain OKM-9

“…20,21) L-Ami-no acids are transported into these bacterial cells via proton-or sodium-dependent amino acid transport systems. The uptake of amino acids by the extremely acidophilic, thermophilic archaeon Picrophilus oshimae 22) has been reported.…”