Desulfovibrio desulfuricans – friend or foe?

by Connor Trottor, PIPS Intern

The National Collection of Industrial, Food and Marine Bacteria includes thousands of industrial strains – but what exactly is an “industrial” strain? The collection includes strains with biotechnological potential, as well strains studied because of the problems they can cause industry. Some strains fall into both categories. Desulfovibrio desulfuricans, may be better known for its role in oilfield souring, microbiologically influenced corrosion and as a producer of toxic gas, but in this blog, PIPS intern Connor Trotter considers some of the positive applications it could have.

Stench

Many bacteria smell. Some can smell quite nice (such as Streptomyces spp.) whereas others leave a particularly foul odour that lingers long after the source has been removed.  The signature fragrance of a bacterium owes to the volatile compounds it releases during its metabolism and, while most bacteria make a mix of volatiles, particular compounds can be overwhelmingly pungent. One common example of this is the metabolic production of sulfur compounds – such as those released by purple phototrophic and sulfate-reducing bacteria. Sulfur possesses a distinct eggy smell and many volatile compounds containing sulfur are referred to as “stench chemicals”, which must be handled with care in a laboratory setting. Whilst the list of bacteria that produce sulfur compounds is long, the undisputed champions of this metabolism are the Desulfovibrio spp. – such as Desulfovibrio desulfuricans (NCIMB 8307).

Originally isolated in 1895 by the one of the founding environmental microbiologists, Martinus Beijerinck, D. desulfuricans (bs. Spirillum desulfuricans) was the first sulfate-reducing bacterium to ever be isolated (Figure 1). Although little was known about the biochemistry behind this metabolism, seminal work by other famed microbiologists, including Postgate and Peck, slowly unravelled a web of dissimilatory sulfate metabolism (DSM) over the next 100 years1.

Intriguing mode of life

Dissimilatory metabolism is an intriguing mode of life. Unlike assimilatory metabolism, dissimilatory metabolism does not incorporate the metabolite into more complex biomolecules. Instead, the metabolite undergoes a redox reaction linked to a separate energy-yielding reaction and the resulting product is released into the environment. For DSM, this means sulfate (SO42-) is taken up by a cell and reduced to sulfide (S2-) via adenosine 5’ phosphosulfate2 (Figure 2). In this, sulfate acts as a terminal electron acceptor which gives D. desulfuricans the ability to grow in anoxic conditions. The resulting sulfide is released into the environment as H2S, a simple yet highly toxic and flammable sulfur gas.

Figure 2: Overview of dissimilatory sulfide metabolism

Detrimental impact

Biogenic H2S production isn’t particularly problematic in nature – it is an incredibly important part of the sulfur cycle. However, sulfur easily reacts with iron, meaning the presence of H2S can be incredibly detrimental to man-made structures. D. desulfuricans being isolated from near a corroding gas main was no coincidence, in fact, D. desulfuricans likely played a significant role in the corrosion of the gas pipe itself.

Whilst two main methods of microbially influenced corrosion exist, the most common is chemical corrosion. Here, sulfate-reducing bacteria form biofilms on metal surfaces, such as steel pipes, and release H2S that reacts with iron in the structure. This iron is solubilised and lost from the pipe, causing corrosion. However, the product of this corrosion, iron sulfide, is also corrosive and so feedback occurs wherein iron sulfide exacerbates further corrosion3. Such corrosion can be incredibly impactful for offshore oil structures and can have huge economic costs if left unchecked. Monitoring corrosion and understanding the local microbiome around oil production facilities is thus of high importance to oil companies. In fact, it is also one of the many services offered at NCIMB: https://www.ncimb.com/service-by-industry/oil-and-gas/oilfield-microbiology/.

Green chemistry potential?

But the relationship between D. desulfuricans and metals isn’t all bad. An interesting interaction between various Desulfovibrio spp. (including D. desulfuricans) and free metals has been noted in which metabolically active cells can accumulate precious metals and produce nanoparticles4. These nanoparticles are particularly interesting because they can be made from catalytically active metals, such as palladium. Indeed, Pd(0) nanoparticles from a related species, Desulfovibrio alaskensis have recently been used to facilitate various biocompatible reactions5,6. Biocompatible chemistry is an extremely promising branch of biocatalysis, expanding the biosynthetic capacity of microorganisms by interfacing them with the vast toolkit of metal catalysis. Advancements, such as the use of microbial nanoparticles, are incremental steps towards developing full green alternatives to common synthetic chemical processes – with a final goal of reducing emissions across the board.

The use of Desulfovibrio spp. as sources of important catalytic nanoparticles derived from waste sources may signal a promising future for the genus within green chemistry. In doing so, perhaps the genus, including D. desulfuricans, can undergo a PR reinvention to not just be known as the oil production facility-destroyers, but also a tool in our future sustainable world.

If you would like to know more about commercial use of strains in our culture collection, or our oilfield microbiology services, get in touch using the form on this page or email enquiries@ncimb.com

References

1)          Rabus, R.; Hansen, T. A.; Widdel, F. Dissimilatory Sulfate- and Sulfur-Reducing Prokaryotes BT  – The Prokaryotes: Volume 2: Ecophysiology and Biochemistry; Dworkin, M., Falkow, S., Rosenberg, E., Schleifer, K.-H., Stackebrandt, E., Eds.; Springer New York: New York, NY, 2006; pp 659–768. https://doi.org/10.1007/0-387-30742-7_22.

(2)         D., P. H. ENZYMATIC BASIS FOR ASSIMILATORY AND DISSIMILATORY SULFATE REDUCTION. J. Bacteriol. 1961, 82 (6), 933–939. https://doi.org/10.1128/jb.82.6.933-939.1961.

(3)         Dennis, E.; Julia, G. Corrosion of Iron by Sulfate-Reducing Bacteria: New Views of an Old Problem. Appl. Environ. Microbiol. 2014, 80 (4), 1226–1236. https://doi.org/10.1128/AEM.02848-13.

(4)         Lloyd, J. R.; Yong, P.; Macaskie, L. E. Enzymatic Recovery of Elemental Palladium by Using Sulfate-Reducing Bacteria. Appl. Environ. Microbiol. 1998, 64 (11), 4607–4609. https://doi.org/10.1128/AEM.64.11.4607-4609.1998.

(5)         Era, Y.; Dennis, J. A.; Horsfall, L. E.; Wallace, S. Palladium Nanoparticles from Desulfovibrio Alaskensis G20 Catalyze Biocompatible Sonogashira and Biohydrogenation Cascades. J. Am. Chem. Soc. 2022, 2 (11), 2446–2452. https://doi.org/10.1021/jacsau.2c00366.

(6)         Era, Y.; Dennis, J. A.; Wallace, S.; Horsfall, L. E. Micellar Catalysis of the Suzuki Miyaura Reaction Using Biogenic Pd Nanoparticles from Desulfovibrio Alaskensis. Green Chem. 2021, 23 (22), 8886–8890. https://doi.org/10.1039/D1GC02392F.

Figure 1 Desulfovirbio delulfuricans grows in Postgate’s media. As it grows it reduces sulfate to sulfide, which binds with dissolved iron in the media creating a black precipitate – iron sulfide.

About the author

Connor is a PhD student in Stephen Wallace’s lab at the University of Edinburgh. He joined NCIMB for a 3-month project as part of his EASTBIO DTP Placement in Industry for PhD Students (PIPS) internship. Connor has worked on screening more than 60 NCIMB strains during his PhD through a Business Interaction Voucher provided by the HVB Network. The work seeks to identify and combine microbial metabolic processes with biocompatible chemical catalysts to develop sustainable processes for chemical syntheses.