Science Progress (2003), 86 (3)
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Science Progress (2003), 86 (3), 157–178
How killed enterobacterial cultures
can activate living organisms to
resist lethal agents or conditions
ROBIN J. ROWBURY
A major aim in many areas of microbiology is to ensure sterility, and even
where this is impossible, to reduce the number of viable organisms occurring
in particular environments to an absolute minimum. This applies in the
aquatic environment, where e.g. water treatment must ensure as complete
absence of viable microbes as possible. It is also crucial in food processing
and production; many food constituents contain appreciable numbers of
viable organisms, even potential pathogens, and the number must be greatly
reduced and in many situations, the presence of viable organisms totally
abolished. Cleaning of food production components and surfaces must also
kill associated microbes. In domestic, hospital and commercial situations,
similar disinfection is critical. Ultimately, the aim is to ensure, if possible,
sterility, with the assurance that microbial problems cannot occur if organisms
are absent. Additionally, however, it has been implicitly assumed that
killed organisms and even killed cultures cannot (except in minor and trivial
ways) influence the behaviour of living organisms that later enter the environment.
The work reviewed here challenges that view and in fact disproves it.
The findings described show that killed enterobacterial cultures, which
prior to killing had phenotypically gained the ability to resist potentially
lethal stresses, can pass on such ability to living organisms that later enter
their environment i.e. that such killed cultures can convey a baleful legacy
to living ones. This phenomenon is so widespread that it is clear that it has
significance for enterobacterial survival in natural waters, in foods and in
food production, in the domestic, commercial and hospital situation, and in
the animal and human body. In fact, in this last area, the likely effect of
killed cultures appears to be of appreciable public health importance. Here,
the ability of appropriate killed cultures to transfer tolerance to acidity,
alkalinity and thermal stress is described, as well as their ability to pass on
sensitisation to acid and alkali. Other work reviewed suggests that killed
cultures can almost certainly transfer the ability to tolerate hydrogen peroxide,
ultraviolet irradiation and metal ions. The serious implications of
this phenomenon are further emphasised by the fact that numerous killing
methods produce cultures effective in tolerance response transfer. All the
evidence suggests that it is extracellular components (extracellular sensing
components, ESCs, and extracellular induction components, EICs), in the
killed cultures which are involved in stress response transfer, and that the
actual stress response induction process depends on interaction of living
organisms with EICs from the killed cultures. It is of note that ESCs and EICs
survive in killed cultures because of their extreme resistance to irreversible
inactivation by lethal levels of stressing agents and conditions. This is in
contrast to the fact that EC activation, namely the conversion of ESC to EIC
occurs on exposure to very low levels of stressors. Not only is this the case,
but in fact high levels of stressors (e.g. those that kill organisms) generally
fail to convert ESC to EIC.
Science Progress (2003), 86 (3), 179–202
Microbial transformation of
metals and metalloids
ANDREA RAAB AND JÖRG FELDMANN
Throughout evolution, microbes have developed the ability to live in nearly
every environmental condition on earth. They can grow with or without
oxygen or light. Microbes can dissolve or precipitate ores and are able to
yield energy from the reduction/oxidation of metal ions. Their metabolism
depends on the availability of metal ions in essential amounts and protects
itself from toxic amounts of metals by detoxification processes. Metals are
metabolised to metallorgano-compounds, bound to proteins or used as
catalytic centres of enzymes in biological reactions. Microbes, as every
other cell, have developed a whole range of mechanisms for the uptake and
excretion of metals and their metabolised compounds. The diversity of
microbial metabolism can be illustrated by the fact that certain microbes
can be found living on arsenate, which is considered a highly toxic metal
for most other forms of live.
Science Progress (2003), 86 (3), 203–234
On the physics of ferroelectrics
J. F. WEBB
The main physical properties of ferroelectric crystals are described, and
the macroscopic and microscopic viewpoints are discussed along with
some applications, such as in capacitors and nonlinear optics. The emphasis
is on physical understanding, while the mathematical level is kept to a minimum
or supplemented by graphical representations to make the article
more accessible.