Luminescent Whole-Cell Cyanobacterial Bioreporter for Measuring Fe Availability in Diverse Marine Environments

Abstract

A Synechococcus sp. strain PCC 7002 Fe bioreporter was constructed containing the isiAB promoter fused to the Vibrio harveyi luxAB genes. Bioreporter luminescence was characterized with respect to the free ferric ion concentration in trace metal-buffered synthetic medium. The applicability of the Fe bioreporter to assess Fe availability in the natural environment was tested by using samples collected from the Baltic Sea and from the high-nutrient, low-chlorophyll subarctic Pacific Ocean. Parallel assessment of dissolved Fe and bioreporter response confirmed that direct chemical measurements of dissolved Fe should not be considered alone when assessing Fe availability to phytoplankton.

Dissolved iron (II) in the Baltic Sea surface water and implications for cyanobacterial bloom development

“…Their study though is not carried out under natural daylight conditions and thus excludes Fe(II). Particularly in the context of iron limitation when the Fe(II) pool is excluded, our data suggest that Fe(II) plays a major role in iron acquisition by phytoplankton, namely diazotrophic cyanobacteria, in the Baltic Sea and may thus alleviate iron limitation as suggested for cyanobacterial bloom development and nitrogen fixation in the Baltic Sea (Stal et al, 1999;Schubert et al, 2007;Boyanapalli et al, 2007).…”

“…Boyanapalli et al (2007), using a luminescent bioreporter approach and water samples from the Gotland Deep station, demonstrate that only a proportion of the dissolved iron fraction is bioavailable and suggest potential iron limitation. Their study though is not carried out under natural daylight conditions and thus excludes Fe(II).…”

Biogeochemical controls on the bacterial populations in the eastern Atlantic Ocean

“…Apart from the effect of offshore transport, atmospheric input of high Fe concentrations may facilitate fast plankton growth followed by its degradation and production of DOM to support the heterotrophic bacterial community. In this context, the bioavailability and solubility of iron may play an important role (Jickells et al, 2005;Boyanapalli et al, 2007). In a recent microcosm experiment, the addition of atmospheric dust caused a drastic increase (12-fold) in the pathogenic Vibrio cholerae population within a day (Lipp and Westrich, 2011).…”

Iron biogeochemistry across marine systems – progress from the past decade

“…Utilization of laboratory based extensive instrumentation such as FlFFF, x-ray spectroscopy with TEM microscopy, as well as bioreporters, molecular techniques and genomic information allow for in depth studies and visualization of Fe limitation and Fe organic matter interactions (e.g. Heldal et al, 1996;Toner et al, 2009;Stolpe et al, 2005) and particularly also of iron bioavailability (Lam et al, 2006;Boyanapalli et al, 2007;Hassler et al, 2006). Nevertheless, some methods still depend on high material/biomass concentrations and future development and work may lead towards more direct measurement techniques overcoming pre-concentration artifacts.…”