Microbial Competition in Aquatic Environment

By: Marco V. Munoz

Fig.1 Comparison between a fixed environment and control cultures (a) Sample of incubated microbes with additional iron granules used as electron donor. (b) Sample of incubated microbes in a control solution (no additional iron). (c) Sample of methane production after environment became sediment-free and iron was replaced by acetate solution.

One key element to preserve diversity in microorganisms of aquatic environments is by the interactions between species that benefit one or both organisms. Previous studies have proposed that acetate produced by acetogens can feed commensal acetoclastic methanogens. However, a recent study carried out by Palacios and colleagues demonstrated that corrosive microbial communities (MIC) such as methanogens and acetogens found in low-sulfide environments in the sea, compete with each other rather than cooperate under the presence of electrons from metals such as iron (Fe0). The researchers collected sediment cores samples from Bothnian Bay, Baltic Sea at a water depth of 15 m. All cultures made from collected samples were tested and examined over a time frame. The analysis identified Sporomusa and Methanosarcina dominated the corrosive microbial communities found in samples based on taxonomy and the number of microbes observed. Microbial cultures with the addition of iron granules demonstrated a much higher production of methane and acetate compared to control cultures and decreased in number of Sporomusa was based on methane production being higher than acetate; Also, acetoclastic methanogens were observed being inactivated after the environment became sediment-free and iron was substituted by acetate solution (Figure 1). This concluded independency and competition for electrons between these two species existing in the same habitat. This is important to understand because microbial induced corrosion accounts for 20% damage to industries which affects the economy and also contributes to water contamination that leads to health and environment issues affecting other living organisms.

Original Article

Palacios PA, Snoeyenbos-West O, Löscher CR, Thamdrup B, and Rotaru AE. (2019). Baltic Sea Methanogens Compete with Acetogens for Electrons from Metallic Iron. The Isme Journal. doi:10.1038/s41396-019-0490-0.