On Mon, Aug 20, 2001 at 10:34:49AM -0400, artillo5@cs.com wrote:
>
> Longer range, there is the question of antibiotic resistance, a growing
> problem in our new century. Will the spread of AgION-coated material
> help make pesky microbes even more resistant to our medicines?
>
> AK Steel and AgION Technologies don't think so. They note that the
> antibiotic pills your doctor gives you to fight infection are organic
> microbials. These attack one particular "site" on the targeted
> organism. Inorganic microbials like AgION's silver zeolite, on the
> other hand, attack multiple sites. That's important because, as AK
> Steel explains in a backgrounder on the subject, "resistance occurs when
> a microorganism develops a mechanism to counteract the mechanism used by
> the antimicrobial. For example, resistance to penicillin was caused
> when certain strains of bacteria produced an enzyme that clipped the
> penicillin molecule in half, rendering it ineffective. The probability
> of developing resistance to a single mechanism used by an antimicrobial
> is much higher than that of developing resistance to the multiple
> mechanisms employed by inorganic antimicrobials."
The problem is that there already exist bacteria that are silver resistant;
they live in waste water from silver mines and protect themselves by forming
silver crystals in a controlled manner (see below).
But that is not likely a major problem. The basic idea of the coating seems
good. There are also bactericidal glasses that might be used at least in
surgical applications. I guess one has to update the protection from time to
time when plasmids with resistance start to spread, but that is just good
for business :-)
Klaus, T., et al. 1999. Silver-based crystalline nanoparticles, microbially
fabricated. Proceedings of the National Academy of Sciences 96(Nov.
23):13611.
http://scienceweek.com/2000/sw000218.txt
2. MATERIALS SCIENCE:
SILVER-BASED CRYSTALLINE NANOPARTICLES FABRICATED BY BACTERIA
Heavy metal ions are usually toxic to biological systems,
although certain heavy metal ions, in trace quantities, serve as
enzymatic catalyst cofactors. Silver is highly toxic to most
microbial cells and can be used as a biocide or antimicrobial
agent. It has been reported, however, that several bacterial
strains are silver-resistant and may even accumulate silver at
the cell wall to as much as 25 percent of the dry weight biomass.
... ... T. Klaus et al (4 authors at Uppsala University, SE)
report the biological synthesis of silver-based crystals in a
bacterial species, the authors making the following points:
1) The authors report the biosynthesis of silver-based
single crystals with well-defined compositions and shapes, such
as equilateral triangles and hexagons, in the bacterium
Pseudomonas stutzeri AG259, a bacterial strain originally
isolated from a silver mine. The crystals were up to 200
nanometers in size and were often located at the cell poles.
Electron microscopy, x-ray analysis, and electron diffraction
studies established that the crystals comprise at least 3
different types in both whole cells and thin sections.
2) In contrast to many other metal-resistant bacteria, for
which efflux of toxic ions is the main detoxification mechanism,
the majority of the accumulated silver in P. stutzeri AG259 is
deposited as particles in vacuole-like granules between the outer
membrane and the plasma membrane (periplasmic space). X-ray
analysis shows silver and sulfur in the proportion 2:1, thus
suggesting Ag(sub2)S (silver sulfide). The electron diffraction
pattern suggests acanthite, a stable crystalline form of silver
sulfide. The authors suggest the formation of acanthite crystals
may be caused by a reaction of silver particles with H(sub2)S gas
produced by P. stutzeri.
3) The authors conclude: "Metal-insulator composite
materials have interesting optical and electrical properties that
favor their application in microelectronics, for example, or as
functional optical thin-film coatings. The possibility of
synthesizing metal particles directly in an organic matrix points
toward new uses of metal-containing bacteria as precursors in
thin film and surface coating technology, for which a composite
or *cermet structure can yield controlled optical, electrical,
and other properties."
-- ----------------------------------------------------------------------- Anders Sandberg Towards Ascension! asa@nada.kth.se http://www.nada.kth.se/~asa/ GCS/M/S/O d++ -p+ c++++ !l u+ e++ m++ s+/+ n--- h+/* f+ g+ w++ t+ r+ !y
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