What’s on the microbial menu?

Every living organism needs the right food to thrive, and microbes are no exception. In gas and hydrogen infrastructure, microorganisms thrive in nutrient-limited, anaerobic environments, feeding on the smallest traces of organic and inorganic compounds. But not all microbes eat the same meal. Understanding who consumes what is key to predicting and managing their impact on your system!

The main microbial players in gas and hydrogen storage are impacting the infrastructure by microbiologically influenced corrosion (MIC) and H₂ consumption.  

1.    Anaerobic Sulfate Reducers

Dissimilatory sulfate reduction is the main energy pathway for strictly anaerobic microorganisms that reduce sulfate to sulfide, producing sulfide as an obligatory intermediate. Besides that, other sulfur compounds like thiosulfate or elemental sulfur are used and also organic compounds might be used in a fermentative way. Together, these microorganisms, known as sulfate-reducing microorganisms (SRMs), including both bacteria and archaea, are among the most significant culprits of reservoir souring and infrastructure corrosion.

A.    Sulfate Reducing Bacteria (SRB)

In anoxic environments, SRBs often use sulfate as an electron acceptor. Electron donors might be present as organic carbon sources, hydrogen, or even metals.Their metabolism produces hydrogen sulfide (H₂S), a toxic and corrosive gas responsible for microbially influenced corrosion of carbon steel, a major concern in pipelines and underground storage facilities.

B.     Sulfate-Reducing Archaea (SRA)

SRAs belong to the domain Archaea that reduce sulfate to sulfide. SRAs play a similar role to SRBs but dominate under more extreme or energy-limited conditions, such as in deep subsurface reservoirs or hydrogen storage caverns. Their corrosion potential is often underestimated.

2.    Methanogens

Methanogenic archaea generate methane (CH₄) through either H₂ + CO₂ (hydrogenotrophic), acetate (acetoclastic) or methyl-based (methylotrophic) pathways. While beneficial for biomethanation, methanogens may be problematic in hydrogen storage infrastructure, as they consume valuable H₂ and alter the gas composition. Their #biofilm formation also impacts gas flow in porous rock storages, influencing both system performance and corrosion dynamics.

3.    Acetogens

Acetogens are a diverse group of anaerobic microorganisms, including both bacteria and archaea, that play a crucial role in accelerating corrosion through their metabolic activities. They transform carbon dioxide (CO₂) and hydrogen (H₂) into acetate, a vital intermediate in anaerobic food webs.

By competing with methanogens for hydrogen, acetogens influence both carbon flow and gas composition in subsurface systems. Certain acetogens, such as Geobacter species, go a step further, reducing metals like iron (Fe(III)) and uranium (U(VI)) while forming electrical connections with extracellular electron acceptors.

Figure 1. Phase-contrast and epifluorescence microscopy of anaerobic microorganisms enriched during a MIC-monitoring campaign at Microbify.(a) Desulfovibrio sp., a typical sulfate-reducing bacterium and heavy H₂S producer, (b) Methanobacterium sp., a methanogenic archaeon that consumes hydrogen.

Understanding Microbial Diets to Protect Infrastructure

Knowing what the microbes eat, and under which conditions they thrive, provides valuable insight into the chemical and biological processes within the gas systems. From SRB-driven corrosion to methanogenic gas alteration, substrate availability directly determines microbial activity.

At Microbify GmbH, we combine molecular biology, chemical analysis and anaerobic microbiology. By identifying the microbes, their food preferences, and their metabolites, we help operators take targeted actions to prevent #corrosion, maintain gas quality, and optimize system performance.