Manuscript linking consumption of atmospheric H2 to the life cycle of soil-dwelling actinobacteria

The presence (left) or absence (right) of aerial hyphae in Streptomyces may influence their atmospheric H<sub>2</sub> consumption
The presence (left) or absence (right) of aerial hyphae in Streptomyces may be linked to atmospheric H2 consumption

Microbe-mediated soil uptake is the largest and most uncertain variable in the budget of atmospheric hydrogen (H2). In Meredith et al. (2014) in Environmental Microbiology Reports, we probe the advantage of atmospheric H2 consumption to microbes and relationship between environmental conditions, physiology of soil microbes, and H2First, we were interested in whether environmental isolates and culture collection strains with the genetic potential for atmospheric H2 uptake (a specific NiFe-hydrogenase gene) actually exhibit atmospheric H2 uptake. To expand the library of atmospheric H2-oxidizing bacteria, we quantify H2 uptake rates by novel Streptomyces soil isolates that contain the hhyL and by three previously isolated and sequenced strains of actinobacteria whose hhyL sequences span the known hhyL diversity. Second, we investigated how H2 uptake varies over organismal life cycle in one sporulating and one non-sporulating microorganism, Streptomyces sp. HFI8 and Rhodococcus equi, respectively. Our observations suggest that conditions favoring H2 uptake by actinobacteria are associated with energy and nutrient limitation. Thus, H2 may be an important energy source for soil microorganisms inhabiting systems in which nutrients are frequently limited.

Much of this work was done with the help of Deepa Rao, an undergraduate researcher at MIT at the time who wrote an award-winning senior thesis on the topic and presented results in a number of venues, including at AGU 2012.


How much energy does H2 supply to soil microbes?

I presented a poster at the at the Ecology of Soil Microorganisms conference in Prague, 2011 on the role of soil microorganisms in dominating the fate of atmospheric molecular hydrogen (H2). Recent work has linked atmospheric H2 uptake to a novel high-affinity [NiFe]-hydrogenase expressed in active Streptomyces sp. cells, and is perhaps not driven by abiotic hydrogenases as was previously thought. Consequently, atmospheric hydrogen may be a 60-85 Tg yr-1 energetic supplement to microbes in Earth’s uppermost soil horizon. To understand the role of this supplement to the soil microbial ecology, this work explores the following questions:

  1. What is the importance of atmospheric H2 energy to soil microbial communities relative to carbon substrates?
  2. How might this energetic supplement change with changes in anthropogenic H2 emissions?
Ecology of Soil Microorganisms poster
Ecology of Soil Microorganisms