Response of two marine bacterial isolates to high CO<sub>2 concentration

Abstract

Experimental results related to the effects of ocean acidification on planktonic marine microbes are still rather inconsistent and occasionally contradictory. Moreover, laboratory or field experiments that address the effects of changes in CO 2 concentrations on heterotrophic microbes are very scarce, despite the major role of these organisms in the marine carbon cycle. We tested the direct effect of an elevated CO 2 concentration (1000 ppmv) on the biomass and metabolic rates (leucine incorporation, CO 2 fixation and respiration) of 2 isolates belonging to 2 relevant marine bacterial families, Rhodobacteraceae (strain MED165) and Flavobacteriaceae (strain MED217). Our results demonstrate that, contrary to some expectations, high p CO 2 did not negatively affect bacterial growth but increased growth efficiency in the case of MED217. The elevated partial pressure of CO 2 (pCO 2 ) caused, in both cases, higher rates of CO 2 fixation in the dissolved fraction and, in the case of MED217, lower respiration rates. Both responses would tend to increase the pH of seawater acting as a negative feedback between elevated atmospheric CO 2 concentrations and ocean acidification. KEY WORDS: Bacterial metabolism · Flavobacteriaceae · Ocean acidification · RhodobacteraceaeResale or republication not permitted without written consent of the publisher Mar Ecol Prog Ser 453: 27-36, 2012 on marine bacterial isolates (Takeuchi et al. 1997, Labare et al. 2010. The latter studies found a decrease in the production and growth rates at pH < 7 -values far from the usual pH observed in ocean waters under present or future scenarios of elevated p CO 2 .Most microorganisms, particularly heterotrophic bacteria, are able to assimilate CO 2 as part of their metabolism through anaplerotic reactions (Roslev et al. 2004). Although light-independent or dark CO 2 assimilation has been usually assumed to be insignificant in oxygenated marine waters, a recent work by Alonso-Sáez et al. (2010) suggests that the global relevance of this process could have been underestimated. Those results show for the first time that high ambient CO 2 concentrations could stimulate CO 2 fixation rates by increasing the CO 2 flux into the cells.A comprehensive understanding of the effect of elevated CO 2 concentration on carbon cycling in the ocean requires the analysis of both production and respiration rates to provide a total carbon budget. However, to the best of our knowledge none of the published studies have simultaneously addressed the effect of CO 2 on BP and respiration, which are essential variables for bacterial growth efficiency (BGE) calculations. Allgaier et al. (2008) did find changes in bacterial taxonomic composition in response to high CO 2 concentrations, which suggest that the effects of elevated p CO 2 are likely to vary among species. Therefore, the aim of the present study was to test the direct effect of elevated CO 2 concentrations (1000 ppmv) on the biomass and metabolic rates (leucine incorporation, CO 2 fixation and respiration...

Interactive network configuration maintains bacterioplankton community structure under elevated CO&lt;sub&gt;2&lt;/sub&gt; in a eutrophic coastal mesocosm experiment

“…In contrast, the HC treatment had negative effects on the growth of Alphaproteobacteria compared to the LC treatment. The results reported here are in line with previous reports about the response of Flavobacteria to ocean acidification in biofilm and single species experiments (Witt et al, 2011;Teira et al, 2012). Flavobacteria are considered as the "first responders" to phytoplankton blooms, because they specialize in attacking algal cells and further degrading biopolymers and organic matter derived from algal detrital particles (Kirchman, 2002;Teeling et al, 2012).…”

“…Under lab conditions, growth of Vibrio alginolyticus, a species belonging to the class Gammaproteobacteria, was suppressed at low CO 2 levels (Labare et al, 2010). In contrast, stimulation of growth was observed for one Flavobacteria species under high CO 2 levels (Teira et al, 2012).…”

Study on the effects of near-future ocean acidification on marine yeasts: a microcosm approach

“…This may hold true for fungi in general, as osmotrophic feeding driven by the plasma membrane proton gradient is a characteristic feature of this group (Davis 2009;Richards et al 2012). The extent to which different species will benefit may depend on their specific pH regulation mechanisms, as was recently proposed for marine bacteria (Teira et al 2012).…”

Effect of CO&lt;sub&gt;2&lt;/sub&gt; enrichment on bacterial metabolism in an Arctic fjord

“…Teira et al (2012) examined the effect of CO 2 on two bacterial strains, Roseobacter and Cytophaga, and demonstrated that respiration of Cytophaga was significantly lower and BGE was higher in the elevated CO 2 treatment than control, while Roseobacter was not affected. Although an increase in the abundance of the phylum Bacteroidetes, which comprises Cytophaga, was observed after nutrient addition (Roy et al, 2013), no effect of pCO 2 on bacterial respiration of the natural community was observed.…”