Exploiting a gaseating bacteria

The Department of Molecular Biology at the University of Bergen (UiB) has developed a research model in their work with the bacteria Methylococcus capsulatus, which combines basic and applied research to the advantage of each.

Sometimes industrial groups come to the university with a research problem. Such was the case when the strategic University of Bergen (UiB) programme, Gas and Biotechnology (GABI), was established. The question was how to exploit the bacteria, Methylococcus capsulatus, to make animal feed. The reason M. capsulatus was selected was because this bacteria has the unique capacity of being able to produce basic nutrient molecules using only the simplest hydrocarbon, methane, as its food source. Most other organisms, including ourselves, cannot do this and need to obtain these basic nutrient molecules from their diet.

In addition its ability to "eat" methane, this bacterium has a number of unique characteristics that make it an interesting model for basic research. Thus the GABI project provided researchers with the opportunity to engage in both applied and basic research work.

The UiB researchers involved in the GABI project came from the Signal Transduction and Thyroid Cancer group at the Department of Molecular Biology (MBI) at UiB. Professor Johan Lillehaug is the leader of this group. They collaborated with the Institute for Genomic Research (TIGR) and Norferm DA in the GABI project. The project was supported by the Norwegian Research Council, the US Department of Energy, Norferm DA and UNIFOB.

The first part of GABI involved the complete sequencing of the bacterial genome. This sequencing should be completed early this summer. The second part of the GABI project involves the characterisation of some of the M. capsulatus genes, in particular those relating to three areas:
1) membrane transport
2) synthesis of building block molecules
3) gene regulation

All of these three areas deal with important basic biological questions. The first two have already led to some interesting applied spin-offs. Basic research work with membrane transport has led to the development of an oral vaccine using M. capsulatus. Basic research work with understanding how M. capsulatus can synthesize biological building block molecules has led to the production of a nutritious feed additive.

Vaccines of the future

Some bacteria species have already been "domesticated" to produce particular compounds such as insulin, for example. Researchers have been exploring how to exploit some of the unique characteristics of M. capsulatus to develop novel vaccines that could be ingested rather than injected.

Intensive farming involves dealing with large numbers of animals. Imagine the process of having to vaccinate several thousand 10cm long smolt (young salmon). You would have to catch the fish, while trying not to traumatise or damage them, and then individually inject each one with the vaccine. This process is very labour intensive, so it is easy to understand the attractiveness of the idea of an oral vaccine to workers in the aquaculture industry.

M. capsulatus is a good vector or vehicle for transporting vaccine material orally because, unlike many other bacteria, it is not toxic. This is because its outer membrane does not contain any protein molecules that act as strong antigens (unlike some strains of Escherichia coli, for example). This means that M. capsulatus can be ingested harmlessly. If M. capsulatus could then be modified to carry a viral coat protein, it could be used as an oral vaccine against that virus.

The green viral proton can be linked to membrane proteins in different ways.

The researchers in Lillehaug's group are well qualified to undertake such modifications. They have been studying membrane transport. They have been trying to elucidate more about the micro-mechanisms involved in the exchange of material across cell membranes. Lillehaug explains that the cell membrane must somehow control what goes in and out of the cell. The identification process is so exact, he says, that membranes can actually distinguish between chiral (mirror-image) molecules.

In order to modify M. capsulatus to create an oral vaccine, they first identified a protein in the virus coat. They then worked backwards to determine the genetic code, or gene, for this protein. The next step was to identify a gene in the bacteria's genome that coded for a protein that formed part of the bacteria's outer membrane. They then inserted the viral protein coat gene into the bacteria's genome such that the two genes would be expressed together. This ensures that the viral protein would also end up being a part of the bacteria's outer membrane. From this position it could trigger an antibody response in the host.

Such vaccines are now used as additives in fish and livestock feed, and are being tested for use in pet food and chicken feed.

Miniature biomass factories

Methanotrophic (methane eating) bacteria have the unique ability of being able to convert methane to biomass (biologically useful compounds). The Norwegian company, Norferm DA has built a plant to scale up production of bioprotein. The company has developed a protocol whereby M. capsulatus are mixed with methane, ammonia and oxygen in a fermentor, where they grow. The process converts one ton of methane to 0.7 tons of biomass (70% protein, 12% carbohydrate, 10% fat and 8% minerals).

Bioprotein increasing nutritive value in animal feed.

The plant that Norferm DA has established for bioprotein production is currently only a pilot operation with an annual production of around 10 000 tons. There are plans to construct similar operations elsewhere.

The success of Norferm DA clearly demonstrates that understanding something about the basic biology of how M. capsulatus can transform methane into biological building blocks, has led to a cost-effective industrial process for increasing the nutritive value of animal feed.

Bacteria and genetics

Lillehaug explains that bacteria are useful organisms for studying genetics. This is because their genetic processes are relatively simple. Their gene regulation, for the most part, only involves "on/off". M. capsulatus, for example, responds to metal ion concentrations for some of its gene regulation. Research involving changing the amount of copper ions available, for example, has shown dramatic effects on M. capsulatus membrane production.

Experimental research can be exciting and unpredicatable. Lillehaug cites some of the early surprising results they had as they began to work with M. capsulatus. At first they found organisms with differently organised DNA. The researchers in Lillehaug's group wondered if these differences due to artefacts or errors? Were there, perhaps, different bacteria present? They even wondered if they had the right organism!

Lillehaug explains that we now understand that the M. capsulatus genome has many insertion elements or transposon sequences. These elements facilitate the movement of whole segments of DNA within the organism. Practically, this means that the organism is very active in re-organising its genes, which in turn implies that it is very adaptable to different environments.

This genetic flexibility is now recognised as being another unique characteristic of this organism and one that, with more research, may help us to understand more about fundamental genetic processes in all organisms.

Building on the M. capsulatus model

Interaction between industrial interests and the university, applied and basic research.

As the sequencing of M. capsulatus draws to completion, Lillehaug feels confident that he and his team could handle a larger sequencing project. They have also developed a successful research model for linking industrial interests, practical applications and basic research. In fact they have submitted a proposal to begin a new project involving the sequencing and study of the salmon louse, a project that also contains considerable industrial and biological interest.

Methylococcus capsulatus

Because of its unique characteristics, the bacteria Methylococcus capsulatus has been attracting research interest since its discovery a couple of decades ago. As its name suggests, M. Capsulatus is a coccus, or roughly spherically shaped, encapsulated bacteria that is methanotrophic, or methane eating.

Methanotropic bacteria can use simple organic materials, such as methane, the simplest of the hydrocarbons (CH4), together with certain minerals to make the building blocks of life (simple sugars, amino acids and fatty acids).

Thus far, researchers have identified very few organisms capable of making these essential molecules. Most organisms, including us, need to ingest these basic molecuules in our diet or make them by breaking sown largerk, more complex molecules.

The idea of an organism that naturally contains the biological pathways to make these fundamental molecules is very interesting. What can it tell us about the origins of life? What can it tell us about how to make such vitally important biological materials? How did it ever come to exist in such an extreme environment in the first place?