Community respiration studies in saltern crystallizer ponds

Abstract

To measure community respiration by the heterotrophic Archaea (dominated by Haloquadratum) and Bacteria (Salinibacter) in the NaCl-saturated crystallizer brines of the solar salterns in Eilat, Israel, and to obtain information on the substrates preferred by the community as energy sources, we used 2 complementary approaches: monitoring of changes in oxygen concentration using planar optode sensors in short (up to 30 min) experiments, and long-term (up to 40-50 h) incubations using Winkler titration to assess changes in oxygen levels. Respiration rates measured were ~3 fmol cell -1 h -1. Respiration was markedly stimulated by glycerol, dihydroxyacetone and pyruvate, but not by yeast extract, succinate, and fumarate. These findings are discussed in view of genomic information on the dominant heterotrophic organisms in the community as well as the outcome of earlier studies on the behavior of halophilic prokaryotes in situ and in laboratory cultures. Despite the low in situ respiration rate, the oxygen uptake studies added information on the activities of the heterotrophic communities in salt-saturated ecosystems and on the substrates metabolized by the microorganisms present.

The Function of Gas Vesicles in Halophilic Archaea and Bacteria: Theories and Experimental Evidence

“…Using a method based on the Winkler titration, Rodriguez-Valera et al [ 60 ] measured 0.3–0.8 mg/L (9–25 μM) oxygen in salt-saturated saltern ponds in Spain. Similar values (~20–27 μM) were estimated for crystallizer brine in the Eilat, Israel salterns [ 61 ]. Such concentrations are probably not limiting to the community of aerobic halophilic microorganisms in any way.…”

Glycerol metabolism in hypersaline environments

“…Another approach to assess the effect of glycerol on the heterotrophic activities in hypersaline environments is by its effect on the community respiration. Addition of glycerol (1 mM) stimulated respiratory oxygen uptake in saltern crystallizer brines up to 50% (Warkentin et al ., ; Oren, ). A similar glycerol‐induced stimulation was reported in the respiratory electron transport activity as measured by the reduction of 2‐( p ‐iodophenyl)−3‐( p ‐nitrophenyl)−5‐phenyl tetrazolium chloride (INT) to INT‐formazan.…”

Lytic failure in cross-inoculation assays between phages and prokaryotes from three aquatic sites of contrasting salinity

“…(Riemann et al, 2009). In hypersaline environments (with salinities higher than 250%), the unicellular microalga Dunaliella salina is known to produce large amounts of glycerol to ensure osmotic stabilization of the cytoplasm, and this compound is often thought to be the main source of organic carbon for the heterotrophic prokaryotes in these systems (Oren, 1995;Elevi Bardavid et al, 2008;Warkentin et al, 2009). In Lake Retba, where Dunaliella is abundant (Y.…”