How Oxygen-Using Bacteria Survive Low Oxygen in Methane-Producing Lake Sediments

Jim Crocker
3rd July, 2024

How Oxygen-Using Bacteria Survive Low Oxygen in Methane-Producing Lake Sediments

To investigate how aerobic methanotrophs survive in low-oxygen environments, this study enriched microbes from Lake Kinneret sediment under either ambient air (a) or hypoxic conditions (b) for subsequent comparative genomic analysis (c).

Image adapted from: Gafni et al. / CC BY (Source)

Key Findings

  • Researchers from Ben-Gurion University studied the adaptability of aerobic methanotrophs in the hypoxic sediments of Lake Kinneret
  • They found that these microorganisms can survive and function in low-oxygen conditions by using specific genes
  • This adaptability suggests that methanotrophs can help control methane emissions in various aquatic environments, even where oxygen levels are low
Microbial methane oxidation, known as methanotrophy, is essential in controlling methane emissions, a potent greenhouse gas, from aquatic ecosystems. While aerobic methanotrophy, which relies on oxygen, is well-documented in oxygen-rich environments, recent studies have shown that these microorganisms might also be active in low-oxygen (hypoxic) conditions. The adaptability of aerobic methanotrophs to such environments, however, has been poorly understood. Researchers from Ben-Gurion University[1] have investigated this adaptability in the methanogenic sediments of Lake Kinneret (LK), providing new insights into how these microorganisms function in hypoxic conditions. Methane is a significant contributor to global warming, accounting for about 20% of the postindustrial increase in global temperatures[2]. A substantial portion of methane production and consumption is driven by microbial processes, yet the specific roles and mechanisms of these microorganisms are not fully understood. Traditionally, methane oxidation has been associated with oxygen or sulfate as electron acceptors. However, recent studies have expanded our understanding of the microbial processes involved in methane oxidation under different environmental conditions. The Ben-Gurion University study focused on sediments from Lake Kinneret, located below the oxidic (oxygen-rich) and sulfidic (sulfur-rich) zones. These sediments were previously noted for methane oxidation coupled with iron reduction, implicating aerobic methanotrophs in the process. This finding challenges the traditional view that aerobic methanotrophy requires high oxygen levels, suggesting that these microorganisms can adapt to hypoxic conditions. The study utilized genetic analysis to explore how aerobic methanotrophs adapt to hypoxia. The researchers examined the genetic material of these microorganisms, identifying specific genes that enable them to survive and function in low-oxygen environments. This genetic adaptability is crucial for understanding how these microorganisms contribute to methane oxidation in various aquatic systems. The findings from Lake Kinneret build on earlier research that has demonstrated the versatility of methanotrophic processes. For instance, the anaerobic oxidation of methane (AOM) has been shown to occur with various electron acceptors such as sulfate, iron, and manganese[3]. More recent studies have identified novel methanotrophic pathways, such as the coupling of AOM to nitrite reduction by the bacterium Candidatus 'Methylomirabilis oxyfera'[3]. Another study revealed that a microbial consortium from anoxic sediments could oxidize methane coupled to denitrification, indicating that methane oxidation can proceed in the absence of oxygen[4]. The Ben-Gurion University study adds to this growing body of knowledge by highlighting the genetic mechanisms that allow aerobic methanotrophs to adapt to hypoxic conditions. These findings are significant because they suggest that methanotrophs are more versatile than previously thought, capable of functioning in a wider range of environmental conditions. This adaptability could have important implications for mitigating methane emissions from aquatic systems, especially in areas where oxygen levels fluctuate. In summary, the research conducted by Ben-Gurion University sheds light on the genetic adaptability of aerobic methanotrophs to hypoxic conditions in Lake Kinneret. By identifying specific genes that enable these microorganisms to survive and function in low-oxygen environments, the study enhances our understanding of methanotrophy and its role in controlling methane emissions. These findings, together with earlier studies on anaerobic methane oxidation[2][3][4], underscore the complexity and versatility of microbial processes involved in methane cycling, offering new avenues for research and potential strategies for mitigating greenhouse gas emissions.

BiochemEcologyMarine Biology

References

Main Study

1) Survival strategies of aerobic methanotrophs under hypoxia in methanogenic lake sediments

Published 2nd July, 2024

https://doi.org/10.1186/s40793-024-00586-1

Related Studies

2) Anaerobic oxidation of methane: progress with an unknown process.

https://doi.org/10.1146/annurev.micro.61.080706.093130

3) Anaerobic oxidation of methane coupled to nitrate reduction in a novel archaeal lineage.

https://doi.org/10.1038/nature12375

4) A microbial consortium couples anaerobic methane oxidation to denitrification.

Journal: Nature, Issue: Vol 440, Issue 7086, Apr 2006


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