Hello

For over 30 years, I have worked with a large diversity of microbes (Bacteria and Archaea) from various environments. Some of these are normal environments while others are special ones without any oxygen or air, have high temperatures exceeding 90℃ (194℉), or even filled with poisonous gases like hydrogen sulfide (rotten-egg smell). 

 

All the microbes in these different and unique environments have evolved specialised means to grow and flourish. And for each specific type of microbe, there are special kinds of lab equipment, environmental conditions, and research experience, needed to grow and study them. 

 

I conducted physiological and genetic research on how the microbes grow in these environments, interact, adapt to environmental fluctuations, exchange nutrients with each other, or produce products harmful towards their competitors.

 

My initial work was on strict anaerobes (Microbes living in environments with no oxygen) and some of their special traits:

 

1.  Biological Nitrogen fixation (at 37℃ and also at 91℃): 

 

Only specialized groups of Bacteria and Archaea (Plants and animals themselves do not) are able to take the nitrogen gas from air and convert it to the essential nutrient ammonium. Ammonium is a building block of amino acids (which make up proteins) and nucleic acids (components of DNA and RNA) and thus feeds plants, animals and other microbes. Without the nitrogen fixing microbes to make bioavailable ammonia for our planet, other microbes, plants and animals would not be able to reproduce. Different types of nitrogen fixing microbes grow in diverse environments with a wide range of temperatures.  Thus, Nitrogen Fixation can occur from temperatures close to freezing to as high as 91℃.

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The only other way of converting nitrogen to ammonium is through a non-biological and much harsher (super hot temperatures of 300 - 500℃ and extremely high pressures of 50-177 times normal atmospheric pressure) process invented by man and named the Harber Bosch process.  This process requires highly specialised and expensive equipment. Thus, it will be useful to create a way to make ammonium at less dangerous conditions.

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My colleagues and I characterized a novel protein, NrpR, which controls gene expression of nitrogen fixation in a Methanogenic Archaeon.  We also discovered that different versions of this protein exist in a diversity of microbes and have conducted some experiments to understand its function.

 

2.  Sulfate (and sulfonate) reducing bacteria 

 

Instead of growing on oxygen in air and reducing it to water like all aerobic organisms, another group of microbes grows on sulfate and reduce it to the toxic gas hydrogen sulfide (rotten egg smell).  Thus, these sulfate reducing bacteria can survive in toxic environments without air.  As these sulfate reducers are also able to breakdown a wide range of chemicals, they are useful for degrading various environmental toxic chemicals down to simpler and safer chemicals in a process termed bioremediation. 

 

My colleagues and I discovered that sulfate reducers had ability to grow on new types of carbon containing sulfur compounds called sulfonates. Examples include Isethionate found in detergents, and Taurine, found in mammels, implying their potentially significant roles even in gut environments.  We also discovered a new species of sulfate reducing bacterium and named it Desulforhopalus singaporensis, after Singapore, the country of my birth. 

 

Sulfate reducing microbes are often responsible for the highly expensive problem of corrosion of industrial equipments around the world as well as creating toxic plumes of sulfide in ever increasing dead zones in oceans which can threaten aquatic life.

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3.  Methanogens:

 

Another special group of microbes are the Methanogens (methane gas generating) which produce the flammable gas as they grow on carbon dioxide. They are similar in size to Bacteria but classified as Archaea due to a variety of traits absent from Bacteria. 

 

Methanogenic Archaea can be found in mammalian (including us) and insect (termite) guts, as well as lake sediments, sewage digesters and even hot springs.  Pound for pound, kilogram for kilogram, Methanogens as a group, annually produce approximately 230 million tonnes of methane (this figure will change).  This gas, when present in the atmosphere, traps heat, and helped moderate extreme temperatures on early earth.  However, together with other greenhouse gases, and in much larger amounts, they can tip the scales of normal earth conditions resulting in unusually warm temperatures.  

 

Microbial generated methane, in many communities, are used as fuel to generate heat or electricity.  Methanogens also work in partnership with other Bacteria to allow the Bacteria to degrade chemicals they they normally cannot do so alone. This is a special partnership termed Syntrophy. This process has impacts in both environmental cycles or in health related processes.

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I was part of a team using a predictive metabolic model of methanogenesis to study how this metabolic pathway was regulated in a Methanogenic Archaeon. The hope, from an industrial perspective, is to be able to manipulate steps in the methanogenic pathway for useful applications. Finally, we also used a genetic approach to discover a critical step in hydrogenotrophic methanogenesis.