Effects of iron limitation on growth and carbon metabolism in oceanic and coastal heterotrophic bacteria

Abstract

We investigated the metabolic response to iron (Fe) limitation of two bacterial strains of Alteromonas macleodii, isolated from a coastal and an oceanic marine environment. Bacteria were grown under Fe‐limited and Fe‐replete conditions, and comparative analyses of cellular properties and total proteomes were conducted. Respiration was reduced by a factor of two in both strains, but the growth rate of the oceanic strain was less affected by Fe limitation (reduced by 1.2‐fold) than the coastal strain (reduced by 2‐fold). Fe limitation led to significant changes in the expression of several key enzymes associated with carbon catabolism, specifically those involved in the citric acid cycle, glycolysis, and oxidative phosphorylation. The strain‐specific overall responses to Fe limitation were in part reflected in different metabolic strategies of the carbon metabolism and energy acquisition. Our study provides novel insights on how Fe limitation can affect bacterial heterotrophic metabolism, and how this could influence the coupling of the Fe and carbon cycles in the ocean.

Vibrio Population Dynamics in Mid-Atlantic Surface Waters during Saharan Dust Events

“…are capable of fixing nitrogen, which requires extremely high amounts of iron as a co-factor (Criminger et al, 2007;Chimetto et al, 2008). Iron availability has a direct effect on Vibrio growth and ability to metabolize carbon and other biologically important macronutrients like N and P (Kirchman et al, 2003;Sunda, 2012;Fourquez et al, 2014). Furthermore, Vibrio can utilize dust leachate filtered through a 0.2 µm pore size membrane (Westrich et al, 2016), suggesting that these often particle-associated microbes are not necessarily reliant on dust particulates for growth, but can utilize dust nutrients in a freeliving state.…”

Saharan dust nutrients promote Vibrio bloom formation in marine surface waters

“…This genetic repertoire suggests that Vibrio are effective competitors for Fe in many different environmental niches. The availability of Fe can also control the metabolism of other nutrients such as N and P, and can limit C utilization, effectively setting limits on growth for both open ocean and coastal heterotrophic bacteria (16,33,34). Potential colimitation is especially important in light of the fundamental contribution of heterotrophic bacteria to the cycling of C in marine ecosystems (33,37).…”

“…The availability of Fe can also control the metabolism of other nutrients such as N and P, and can limit C utilization, effectively setting limits on growth for both open ocean and coastal heterotrophic bacteria (16,33,34). Potential colimitation is especially important in light of the fundamental contribution of heterotrophic bacteria to the cycling of C in marine ecosystems (33,37). Vibrio and other rapidly responding heterotrophs likely play a pivotal, but as yet largely unexplored, role, in coupling Fe flux with C cycling in marine food webs, ultimately influencing global climate processes (18,19,37).…”

“…Although the response of marine autotrophs to dust deposition has been investigated (15,25), the full biological response to the episodic deposition of dust-Fe to ocean surface water, especially among microbial communities, has yet to be clearly elucidated. Evidence is growing that heterotrophic bacteria, especially among the class γ-proteobacteria, may play a role in processing deposited minerals and nutrients (31,32), but studies to date, which have largely focused on bulk bacterial response and longer timescales, have shown equivocal results (33,34). We hypothesized that specific opportunistic bacteria, like Vibrio, can respond quickly to newly available dust-associated Fe and suggest a role of dust-Fe as a driver of Vibrio population dynamics.…”

Central role for ferritin in the day/night regulation of iron homeostasis in marine phytoplankton

“…When a precise control of the iron concentration and speciation were required, we used AQUIL medium (41,42) with 100 μM EDTA. Different final concentrations of total iron were obtained by adding different amounts of Fe(III) EDTA complex.…”