This paper, by Yakimov et al. (2007), is a review of the latest results relating to the biogeography, ecophysiology, genomics and potential for biotechnological applications of obligate hydrocarbonoclastic bacteria (OHCB). These bacteria are a group of marine hydrocarbon-degrading bacteria which have been shown to play a significant role in the biological removal of petroleum hydrocarbons from polluted marine water.
A number of oil-degrading bacteria have been isolated but less than a quarter have been obtained from marine sources. Nineteen genera of Eubacteria have been characterised as indigenous marine organisms. Two strains of the Firmicutes and Bacteroidetes phyla have been isolated. The remaining aerobic marine hydrogen-degrading isolated are associated with α- or the γ-Proteobacteria subclasses. The first OHCB to be described was Alcanivorax borkumensis. Since then others have been described which include; A. borkumensis, A. jadensis, A. dieselolei, C. pugetii and C. oligotrophus.
At the end of 2006, more than 250 Alcanivorax-affiliated bacteria had been isolated in all types of marine environments: surface water, sediments, hydrothermal vents and mud volcanoes, shallow and deep sea water bodies, ridge flank crustal fluid and grey whale carcasses. The temperature in which OHCB’s can survive varies with the different strains. T. oleivorans and Cycloclasticus spp. are widely distributed in the Northern hemisphere. The distribution of the psychrophilic OHCB Oleispira antartica is thus far limited to colder waters.
Organisms genetically analysed so far exhibit features typical of oligotrophic bacteria. The most detailed study took place on C. oligotrophus. The cytoplasm was shown to be very dilute, with a dry mass per cell 7-8 times lower than that of Escherichia coli. The outer cellular membrane is enriched for a wide range of transport systems for the capture of nutrients and diverse oligo-elements from the generally nutrient-poor environment.
An influx of oil in marine sites causes population densities of OHCB to increase by up to 90%, with aliphatic hydrocarbon-degraders being the first to bloom. This is followed by microbes (in particular Cycloclasticus spp.) which are specialised for the remaining compounds which are more difficult to degrade.
Marine hydrocarbon-degrading microorganisms can efficiently degrade hydrocarbons and so can be used in oil spills. However more knowledge is needed on the critically important activities and roles of predators and grazers on the composition population dynamics and ecophysiological functioning of marine oil-degrading communities. OHCBs have been shown to have a degrading effect on PHAs. The recent discovery of OHCBs means that their enzyme repertoires are so far incomparable. They do have the potential in biocatalysis, the enzymatic biosynthesis of fine chemicals and added value compounds. Some novel enzymes have been retrieved as a result of a metagenome expression library of crude-oil enrichment, functional screening of the library resulted in the identification of five groups of carboxylhydrolase. All retrieved enzymes were characterised biochemically and exhibited good potential for biosynthetic applications.
Overall, more research needs to go into OHCBs in order to discover their full potential. This is a good paper as it brings together lots of studies and identifies key features regarding OHCBs.
Yakimov M.M, Timmis K.N, and Golyshin P.N. 2007. ‘Obligate oil-degrading marine bacteria’. Current Opinion in Biotechnology. 18 (3). 257-266.
Hi Sophie,
ReplyDeleteI found this review quite neat. It advocated what actions need to be taken in order to explore the potential biotechnological applications of these hydrocarbon-loving bacteria.
From reading your post i decided to look at a recent paper that investigated enriching the function of oil-degrading bacteria. The researchers did begin to explore the community diversity of the involved marine microbes, but didn't really delve into the dynamics beween differing microbes within the population. They did however, discuss the effect oil presence has on the ecophysiological functioning of the community.
Since the review was published, Do you know if there has been any investigations into the activities and roles of predators and grazers within the microbial population?
Thanks!
Carys
Hi Carys,
ReplyDeleteWhat paper was that? I would be interested to read it.
The only paper that I could find that looks into predators and grazers is one by Dalby et al. (2008). They found that the addition of oil alone did not result in an increase of bacteria or their predators. However, the addition of oil and emulsifiers did cause an increase in bacteria followed by nanoflagellate predator response. I've put a link to the paper below if you want to read more about it.
Sophie
http://onlinelibrary.wiley.com/doi/10.1111/j.1462-2920.2007.01428.x/full
Hi Sophie, great post!
ReplyDeleteAs you said in your post oil-degrading microorganisms have been found in all marine environments, but the OHCB's presumably are living off of other carbon sources and therefore not obligate? Sorry but im alittle confused!
Its because Im wondering where natural sources of hydrocarbon compounds would come from in the marine environment? are there seeps in the sediment which slowly leak oil? or is there oil within the sediments naturally? or is it run off from terrestrial environments? or somewhere completely different? Todays lecture with Bradley got me thinking :)
Thanks, Myles
It says in the paper that in contrast to terrestrial hydrocarbon degraders which tend to be metabolically versatile and utilize a large range of organic substances, their marine counterparts are mostly highly specialized obligate hydrocarbon utilizers (these are the OHCBs). The natural sources of hydrocarbon compounds come from natural seeps of oil and natural gas deposits, marine oil transport accidents and deliberate discharges, and from biomass and biological processes.
ReplyDeleteI hope this helps!
Sophie