Shampoo consuming Bacteria

Why Pseudomonas is able to withstand attacks of hygiene

19.05.2006

The pernicious bacterium Pseudomonas aeruginosa is able to persist in the human respiratory tract for long periods of time and also frequently causes acute infections in open wounds especially following open surgery. It is able to resist common house-hold detergents making it difficult to eradicate by normal hygiene routines.


Scientists from the German Research Centre of Biotechnology (GBF) and the Hannover Medical School (MHH) have now identified the reason why these bacteria are resistant to detergents: Pseudomonas secretes an enzyme SdsA that cleaves SDS or Sodium dodecylsulfate - a constituent of many foaming personal hygiene products such as toothpaste, shampoo and shower gels. SDS is a detergent that kills most bacteria by dissolving their surrounding membrane. Pseudomonas aeruginosa protects itself by secreting SdsA, which cleaves and inactivates SDS. The team that includes scientists from Göttingen and Darmstadt in addition to those from Braunschweig and Hannover has now published its results in the prestigious scientific journal Proceedings of the National Academy of Sciences USA (PNAS).


Shampoo as a favorite dish


Using X-ray crystallography, the scientists solved the three-dimensional structure of SdsA at near atomic resolution permitting them to watch the enzyme as it cleaves SDS. The researchers discovered that the bacteria absorb the resulting fragments of SDS utilizing them as nutrients.


The ability of Pseudomonas to resist SDS and to utilize the cleavage products probably explains why this pathogen is frequently found in locations that we prefer to maintain in pristine condition: these include bathroom basins, dishwashers and shampoo bottles. "Apart from the risk to human health, the economic damage can be daunting", concludes GBF group leader Dr. Wolf-Dieter Schubert, "Recalling contaminated products is not only costly, but is particularly damaging to the carefully maintained image of the companies involved."


While SdsA helps to make Pseudomonas dangerous to humans, the cleavage of SDS has its beneficial aspects as well. The bacteria, which live in rivers and even sewage treatment plants, destroy SDS and similar contaminants introduced into the environment as part of normal human behavior.


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Detailed Information provided by the original article: G. Hagelüken, T. M. Adams, L. Wiehlmann, U. Widow, H. Kolmar, B. Tümmler, D. Heinz, W.-D. Schubert: The crystal structure of SdsA1, an alkylsulfatase from Pseudomonas aeruginosa, defines a third class of sulfatases. Proceedings of the National Academy of Sciences, 2006, Vol. 103, N. 20, pp. 7631-7636.




Photo legend


Sdsa_01
The three-dimensional structure of the SDS-degrading enzyme SdsA from the bacterium Pseudomonas aeruginosa: The structure is presented as a ribbon diagram. The colored dots in the background represent individual atoms in SdsA crystals.


Sdsa_02
An abstract display of the three-dimensional structure of SdsA: The pale-yellow spheres represent zinc-ions that are essential for the cleavage of the detergent SDS. The structural regions of the protein – each of which has a distinct function – are marked in different colors: blue (catalysis), orange (binding suitable molecules to pass on to the catalytic domain) and green (binding two molecules of SdsA into a functioning unit.)


Sdsa_03
The catalytic site of the enzyme SdsA: Two zink ions (yellow spheres) activate two water molecules (red dots), so that they can attack and split the SDS-molecule – held by orange-colored amino acids. The products of the reaction (pale blue/green) at first stay bound to the enzyme before being released to the surrounding.

 

MWPI_2005_Lab19_dhs  (Photo: GBF /Bierstedt)
GBF scientist Wolf-Dieter Schubert in his lab.

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