Microbial biodegradation of hydrocarbons seems to be a valid tool in the control of this kind of pollution, although the process can be affected by several factors, especially by the physico-chemical characteristics of the compound and the environmental conditions where pollution occurs.
The aim of this study was to estimate the efficiency of diesel oil utilization by marine Antarctic bacteria at high (20C) and low (4C) temperatures.
Two bacterial strains E28 and E60 were isolated from coastal seawater samples collected in Terra Nova Bay (Ross Sea, Antarctica) and characterized as psychrotrophs and oild degrading bacteria.
A bacterial suspension comprised of E28 and E60 was inoculated in a specific liquid medium containing commercial diesel oil. The liquid cultures were then incubated at high and low temperature for 60 days. At a given incubation time, bacterial abundance was estimated by colony-forming units (CFU) spread plating on Marine Agar medium.
Biodegradation of diesel was quantified using gas-cromatography analysis and was expressed as the percentage of diesel oil degraded compared to the amount of the remaining fraction in the appropriate abiotic control samples (liquid medium uninoculated).
After 60 days of incubation up to 90% of the commercial oil disappeared from the culture medium inoculated with strains E28 and E60 overall, although the response slightly varied according to the strains and the temperatures.
The two isolates differed in the biodegradion dynamics: E28 was generally more efficient at 4C than at 20C during the first period of incubation, after that the biodegradation rapidly increased at 20C, while E60 degradation was always higher at the higher temperature.
These results prove that the temperature has a relevant effect on the biodegradation process in marine environment. Both viable counts and degradation efficiency were higher at 20C than at 4C, likely due to the decrease in enzymatic activity at low temperature and the change in the physico-chemical parameters of the oil (viscosity).
Neverthless psychrotrophic micro-organisms seem to possess an intrinsic advantage in the oil degradation at low temperature, thus more in situ investigations need to be done in order to estimate their real efficiency in degrading oil.
2 comments:
Hi Vale, nice one!
I was just wondering why did the authors of this study have choosen to conduct the experiment only at 4 and 20°C.
It is a bit weird to me since I guess in antarctica water temperature is often much lower than 4°C.
Since they found that oil degradation is less effective at low temperature, in the wretched event of an oil spill down there, it looks like it will be really really difficult to use any known microbial oil degradation technique.
In my opinion it would have been more interesting and representative, evaluating the oil degradation efficiency also at more typical antarctic temperature, such as 0 °C or -1 °C.
But in the end, I really hope that we will be so clever and farsighted to avoid an oil spill in one of earth's last unspoiled paradise, it would be a shame...really.
I totally agree with you:4°C can be reasonable perhaps during the summer,but 20°C seems to be quite unrealistic.
I suppose that the main aim of this study was to investigate the ability of psychrotrophic bacteria in degrading hydrocarbon rather than their application in bioremediation in occurring oil-spill..nevertheless,as the authors stated, psychrotrophic bacteria are more tolerant to temperature compared to others:the optimum for some psychrotrophic strains is between 15 and 20°C, so their distribution is wider than psychrophiles, which do not grow at that temperature.On the other hand mesophiles, which are present in both temperate and cold environments, have a low degradation activity below 10°C...so psychrotrophic are widely distributed and more capable in oil degradation than other bacteria thus they seem the suitable candidates for bioremediation..however, we must bear in mind that the bioremediation process may not benefit from the addition of allochtonous bacteria,as the indigenous community has the main role in the process...
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