Indigenous vs. Exotic: Biodegradation faceoff

A review of: Akinde, S.B., Iwuozor , C.C., Obire, O. (2012). Alkane Degradative Potentials of Bacteria Isolated From the Deep Atlantic Ocean of the Gulf of Guinea. Journal of Bioremedation and Biodegradation. 3 (1), 1-6.

Heterotrophic bacteria are fundamental in the marine environment. They serve as biological mediators through their involvement of biogeochemical processes such as: biological transformation of organic matter and production of carbon dioxide. In the marine environment, 90% of heterotrophic bacteria are Gram negative rods with a variety of different characteristics. The majority of the isolates belong to the genera Pseudomonas, Vibrio and Flavobacterium and can all be linked with bioremediation and biodegradation processes in the marine environment.

Oil producing areas of Nigeria have experienced the devastating consequences of crude oil spills to both terrestrial and aquatic environments in the past 50 years. The absence of adequate and qualitative scientific baseline data restricts quick responses to these pollution events. Some previous efforts have been ineffective and as a result oil spills can be left for natural microbial populations to degrade crude oil spills. For this reason the authors believe it is important to test the crude oil degradative capabilities of indigenous microbiota. They aimed to observe the potential of hydrocarbon utilizing heterotrophic bacterial isolates of deep Atlantic Ocean to degrade total petroleum hydrocarbon or alkane components of crude oil.

They collected bacterial isolates from the: seawater surface, seawater bottom and the superficial sediments of the Atlantic Ocean. They compared them with isolates known to possess oil degrading capability, which had similar morphological and biochemical characteristics, from an oily waste water reservoir. The isolates initially cultured in a marine broth to increase abundance. Flasks containing a high grade crude oil were then inoculated with the bacterial isolates and incubated. Uninoculated flasks were used as a control. The culture flasks were harvested at days 1, 15 and 30 for determination of the quantity as well as individual components of total petroleum hydrocarbon degraded. The extracts were analysed by gas chromatography

All four isolates were capable of degrading crude oil. Surprisingly they all degraded a similar percentage of the crude oil over the 30 days (between 78-85%). The range of carbon compounds that were degraded suggests that all isolates possessed broad enzymatic capacity for crude oil hydrocarbon degradation. It would be expected that the isolate from the oily wastewater reservoir would show the highest degradative capabilities due to its previous exposure to the hydrocarbon compounds found in crude oil. Despite this all of the other isolates demonstrated similar crude oil degradative potential without any prior exposure to crude oil in their natural habitat.

This is a promising study because it demonstrates potential for an environment-friendly bioremediation approach in deep Atlantic Ocean of the Gulf of Guinea. The capability of indigenous bacteria to degrade crude oil reduces the need to use of exotic bacterial strains and chemicals. The reliability of these results could be argued to be limited as it would have been beneficial to include strains from a wider geographical area to yield a better knowledge of the diversity and attributes of this bacterial group. Also I found it strange that the culture flasks were harvested at such widespread intervals. The rate of degradation amongst the strains could have been more accurately monitored with more frequent sampling.