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Synthesis of rhamnolipid biosurfactant and mode of hexadecane uptake by Pseudomonas species.

Cameotra SS, Singh P - Microb. Cell Fact. (2009)

Bottom Line: With an aim to gain more insight into hydrocarbon uptake mechanism, an efficient biosurfactant producing and n-hexadecane utilizing Pseudomonas sp was isolated from oil contaminated soil which was found to produce rhamnolipid type of biosurfactant containing a total of 13 congeners.Involvement of biosurfactant was further confirmed by electron microscopic studies.We report here a new and exciting line of research for hydrocarbon uptake involving internalization of biosurfactant covered hydrocarbon inside cell for subsequent breakdown.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of Microbial Technology, Sector 39A, Chandigarh, 160036, India. ssc@imtech.res.in.

ABSTRACT

Background: Microorganisms have devised ways by which they increase the bioavailability of many water immiscible substrates whose degradation rates are limited by their low water solubility. Hexadecane is one such water immiscible hydrocarbon substrate which forms an important constituent of oil. One major mechanism employed by hydrocarbon degrading organisms to utilize such substrates is the production of biosurfactants. However, much of the overall mechanism by which such organisms utilize hydrocarbon substrate still remains a mystery.

Results: With an aim to gain more insight into hydrocarbon uptake mechanism, an efficient biosurfactant producing and n-hexadecane utilizing Pseudomonas sp was isolated from oil contaminated soil which was found to produce rhamnolipid type of biosurfactant containing a total of 13 congeners. Biosurfactant action brought about the dispersion of hexadecane to droplets smaller than 0.22 mum increasing the availability of the hydrocarbon to the degrading organism. Involvement of biosurfactant was further confirmed by electron microscopic studies. Biosurfactant formed an emulsion with hexadecane thereby facilitating increased contact between hydrocarbon and the degrading bacteria. Interestingly, it was observed that "internalization" of "biosurfactant layered hydrocarbon droplet" was taking place suggesting a mechanism similar in appearance to active pinocytosis, a fact not earlier visually reported in bacterial systems for hydrocarbon uptake.

Conclusion: This study throws more light on the uptake mechanism of hydrocarbon by Pseudomonas aeruginosa. We report here a new and exciting line of research for hydrocarbon uptake involving internalization of biosurfactant covered hydrocarbon inside cell for subsequent breakdown.

No MeSH data available.


GC analyses of extracted intracellular hydrocarbon from cells of SSC2 at different times of growth. Right panel shows 2% n-hexadecane as standard. Peak at Retention time around 12.9 corresponds to that of n-hexadecane (unmodified substrate).
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Figure 5: GC analyses of extracted intracellular hydrocarbon from cells of SSC2 at different times of growth. Right panel shows 2% n-hexadecane as standard. Peak at Retention time around 12.9 corresponds to that of n-hexadecane (unmodified substrate).

Mentions: GC analyses of intracellular hydrocarbon from cells grown on hexadecane revealed the presence of unmodified hexadecane in the numerous inclusions (Figure 5). A number of peaks were present in the chloroform extract of cells grown for different days on n-hexadecane as well as glucose but a peak at RT of 12.5 minutes (average) was observed to be present in cells grown on hydrocarbon while it was absent in the glucose grown cells. This peak was found to be n-hexadecane as was evident after GC analyses of 2% hexane solution of n-hexadecane. Earlier, a comparative analysis of the ultrastructural changes upon hydrocarbon uptake was done in a variety of hydrocarbon oxidizing microorganisms and in almost all the cases, growth in hydrocarbon was characterized by the presence of intracellular electron-transparent inclusions which appeared to be membrane bound and upon analyses were found to be respective hydrocarbon growth substrate [31]. In the present study too, presence of unmodified hexadecane was observed in cells grown at different time intervals and they appeared membrane bound.


Synthesis of rhamnolipid biosurfactant and mode of hexadecane uptake by Pseudomonas species.

Cameotra SS, Singh P - Microb. Cell Fact. (2009)

GC analyses of extracted intracellular hydrocarbon from cells of SSC2 at different times of growth. Right panel shows 2% n-hexadecane as standard. Peak at Retention time around 12.9 corresponds to that of n-hexadecane (unmodified substrate).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2664780&req=5

Figure 5: GC analyses of extracted intracellular hydrocarbon from cells of SSC2 at different times of growth. Right panel shows 2% n-hexadecane as standard. Peak at Retention time around 12.9 corresponds to that of n-hexadecane (unmodified substrate).
Mentions: GC analyses of intracellular hydrocarbon from cells grown on hexadecane revealed the presence of unmodified hexadecane in the numerous inclusions (Figure 5). A number of peaks were present in the chloroform extract of cells grown for different days on n-hexadecane as well as glucose but a peak at RT of 12.5 minutes (average) was observed to be present in cells grown on hydrocarbon while it was absent in the glucose grown cells. This peak was found to be n-hexadecane as was evident after GC analyses of 2% hexane solution of n-hexadecane. Earlier, a comparative analysis of the ultrastructural changes upon hydrocarbon uptake was done in a variety of hydrocarbon oxidizing microorganisms and in almost all the cases, growth in hydrocarbon was characterized by the presence of intracellular electron-transparent inclusions which appeared to be membrane bound and upon analyses were found to be respective hydrocarbon growth substrate [31]. In the present study too, presence of unmodified hexadecane was observed in cells grown at different time intervals and they appeared membrane bound.

Bottom Line: With an aim to gain more insight into hydrocarbon uptake mechanism, an efficient biosurfactant producing and n-hexadecane utilizing Pseudomonas sp was isolated from oil contaminated soil which was found to produce rhamnolipid type of biosurfactant containing a total of 13 congeners.Involvement of biosurfactant was further confirmed by electron microscopic studies.We report here a new and exciting line of research for hydrocarbon uptake involving internalization of biosurfactant covered hydrocarbon inside cell for subsequent breakdown.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of Microbial Technology, Sector 39A, Chandigarh, 160036, India. ssc@imtech.res.in.

ABSTRACT

Background: Microorganisms have devised ways by which they increase the bioavailability of many water immiscible substrates whose degradation rates are limited by their low water solubility. Hexadecane is one such water immiscible hydrocarbon substrate which forms an important constituent of oil. One major mechanism employed by hydrocarbon degrading organisms to utilize such substrates is the production of biosurfactants. However, much of the overall mechanism by which such organisms utilize hydrocarbon substrate still remains a mystery.

Results: With an aim to gain more insight into hydrocarbon uptake mechanism, an efficient biosurfactant producing and n-hexadecane utilizing Pseudomonas sp was isolated from oil contaminated soil which was found to produce rhamnolipid type of biosurfactant containing a total of 13 congeners. Biosurfactant action brought about the dispersion of hexadecane to droplets smaller than 0.22 mum increasing the availability of the hydrocarbon to the degrading organism. Involvement of biosurfactant was further confirmed by electron microscopic studies. Biosurfactant formed an emulsion with hexadecane thereby facilitating increased contact between hydrocarbon and the degrading bacteria. Interestingly, it was observed that "internalization" of "biosurfactant layered hydrocarbon droplet" was taking place suggesting a mechanism similar in appearance to active pinocytosis, a fact not earlier visually reported in bacterial systems for hydrocarbon uptake.

Conclusion: This study throws more light on the uptake mechanism of hydrocarbon by Pseudomonas aeruginosa. We report here a new and exciting line of research for hydrocarbon uptake involving internalization of biosurfactant covered hydrocarbon inside cell for subsequent breakdown.

No MeSH data available.