The Mariana Trench is the deepest known site in the Earth’s oceans, reaching a depth of over 11,000 meters at the Challenger Deep. Recent studies have revealed the trench waters host distinctive microbial planktonic communities. However, the genetic potential of microbial communities within this zone is poorly understood.

Now, a study from researchers led by the University of East Anglia undertakes the most comprehensive analysis of microbial populations in the trench. The team states they have discovered a unique oil-eating bacteria in the Mariana Trench, where it is in the highest abundance of anywhere else on earth. The opensource study is published in the journal Microbiome.

The mysterious Mariana Trench

Previous studies show the Mariana Trench is located in the Western Pacific Ocean and reaches a depth of approximately 11,000 meters. By comparison, Mount Everest is 8,848 meters high. To date, only a few expeditions have investigated the organisms inhabiting this ecosystem. The current study collects samples of the microbial population at the deepest part of the Mariana Trench, some 11,000 meters down, pulling up a new ‘oil-eating’ bacteria.

The current study performs an extensive analysis of microbial populations and their genetic potential at different depths in the Mariana Trench. Results show an abrupt increase in the abundance of hydrocarbon-degrading bacteria at depths over 10,400 meters in the Challenger Deep. Data findings show the proportion of hydrocarbon-degrading bacteria found in the trench is the highest observed in any natural environment on Earth.

Aliphatic fuel degrading bacteria

Results show the bacteria found were mainly Oleibacter, Thalassolituus, and Alcanivorax genera, all of which include species known to consume aliphatic hydrocarbons, which are the main constituent of aliphatic fuels including methane, acetylene, and liquefied natural gas. Data findings show the depth-related shift towards these hydrocarbon degraders is accompanied by increased abundance and transcription of genes involved in alkane degradation.

The team surmises they have identified alkane-degrading bacteria in the deepest part of the Mariana Trench at a proportion higher than observed anywhere else on Earth. For the future, the researchers state their study raises important questions that warrant further investigation in this unique environment.

Source: University of East Anglia  

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