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Biodegradation in case of polycyclic hydrocarbons by
Submitted by Jacky Foo on Mon, 22/05/2006 - 14:53.
>The article is "Biodegradation of soil-adsorbed polycyclic
>hydrocarbons by the white rot fungus Pleurotus ostreatus"
>The white rot fungus, Pleurotus ostreatus, metabolized four
>adsorbed polycyclic aromatic hydrocarbons:50% of pyrene
(0.1 mg g_1
>dry soil), 68% of anthracene and 63% of phenanthrene were
>after 21 d.
The experiments were set up for the degradation of the
various chemicals (upto 21 days) with or without surfactants
in Pleurotus inoculated soils.
(1) I did not see a control sample with out Pleurotus in the
Is this needed ?? Would soil without Pleurotus show any
degradation of chemicals ?
(2) the study was done until 21 days. I wonder how long it
would take for to completely degrade all the chemicals in
the experiments and why the authors have avoided to provide
such an information ?
Biodegradation in case of polycyclic hydrocarbons by
Submitted by Jacky Foo on Mon, 22/05/2006 - 15:11.
To Kenneth Yongabi
The work of Facundo J. M´arquez-Rocha et al (Biotechnology
Letters 22: 469–472, 2000) indicated that even Pleurotus
ostreatus alone degraded chemicals and enhanced even more
Q: In your experimentations, did you sterilise the mushroom
spent substrate before it was used ?
Sterilisation would kill all the microbes in the spent
substrate and enable you to avoid the addition of microbes
which may influence your experiments.
use of compost as an absorbant
Submitted by IOBB Editor on Tue, 23/05/2006 - 06:17.
From: Edo McGowan
Sent: 22 May 2006 18:26
some time ago, .....(cut)... there was some discussion of
spreading or incorporating sewer sludge into land where
there had been oil spills. While at first glance this seems
like a plausible solution to a process that would mix two
undesirables into a viable solution to a problem, it is not
without side effects such as the spread of antibiotic
resistance, hence public health implications.
Also with incorporation of engineered microbes, there may
accompanying spread of antibiotic resistance from the
methods used in the engineering processes that develop these
In this latter case, antibiotic resistant sections of
genetic material are incorporated into the microbe’s
structure. These organisms can then be selected out because
they are now resistant to an antibiotic challenge, but the
markers are left within the final product.
Exposure to heavy metals and toxins for example, will also
select for resistance, and this resistance can cross to that
capable of supplying resistance to antibiotics. The cellular
machinery developed for one is similar to that needed for
Recent articles in the press have noted that there is the
development of “superbugs”, i.e. germs or pathogens that
have become resistant to even the most potent currently
available antibiotic. This may bring in an era where
infections are unstoppable. This thought is not new and this
same idea was introduced to the U.S. Congress by the World
Health Organization’s head of infectious disease several
years ago. The WHO has for some time noted that antibiotic
resistance amongst these superbugs or professional pathogens
has been rapidly increasing and has now reached a global
crisis. This is actually a preparedness issue, especially if
there is a major infectious disease epidemic.
As to antibiotic resistance, the medical community may be
tuned in, the average citizen is not, especially where
health care systems are oversubscribed to non-existent as in
many of the developing nations. In this case there is no
preparedness. Lets look at some reasons for the development
of supebugs and their antibiotic resistance. In scientific
and medical circles, much of the underlying cause is well
known but this information fails to reach the average
citizen. Thus citizens are unable to prepare.
Two decades ago, superbugs were mainly confined to hospitals
and other facilities where large numbers of very sick people
were maintained on antibiotics. The fecal material and urine
were often merely flushed into the local sewer and thus
enter sewer works in large numbers. A very good coverage of
this is found within the writings of Vikrant Chitnis of
These super bugs or professional pathogens are now emerging
outside of the hospital and are found increasingly within
the local communities across this and other nations. This
problem is augmented by over prescribing or over use of
antibiotics, especially for viral infections since
antibiotics have essentially no effect on viruses. In many
countries, there is no need for a doctor’s prescription as
one can just go to the local pharmacy and buy what is felt
to be needed. Additionally, many drug manufacturers are
setting up business in countries where there are lax
environmental regulations. Studies on discharge to rivers
down stream from such plants have often found astonishingly
large numbers of highly resistant organisms.
Another reason we are seeing the spread of antibiotic
resistance is the excessive use of drugs within feeds used
to raise food-animals. This is seen within these large
operations where antibiotics are used not for disease
control but merely for rapid weight gain. These drugs are
added to feed mixes in small but constant amounts. This
creates antibiotic resistance, which is found in the manure
and also in the finished raw product. The derived product
carrys these resistant microbes and the resistant pathogens
are later transferred to the consumer, usually by heavily
contaminating the kitchen surfaces. Once thus contaminated,
these surfaces are extremely hard to disinfect.
Another way for the spread of antibiotic resistance, but
seldom discussed, is the inadequate treatment of sewage. As
now operated, sewer plants across the world’s nations are
manufacturing billions of antibiotic resistant pathogens and
discharging them into the environment.
Part of this problem accrues from people in the more
affluent nations flushing unused and dated antibiotics into
Part of the excess flushing of antibiotics is also from
nursing homes, at least in the United States. In the U.S.
the federal Drug Enforcement Administration, mandates that
dated and unused drugs to be dumped into the toilet. This
adds very impressive volumes of unused and dated drugs into
the toilets each year, which wind up in the sewer works. The
problem is that sewer plants were never designed to deal
with these inputs.
Sewer plant designs have been recently under review for just
such reasons but unfortunately the main agency responsible
for their operation in the United States, for example, is
the U.S. EPA with demonstrably poor staffing in the areas of
emerging and communicable disease. The EPA has steadfastly
refused to seriously look into this issue, especially the
issue of antibiotic resistance.
As the sewage is processed from the moment it enters a
treatment plant and then courses through the sewer works,
there is increased survival pressure placed on bacteria and
other pathogens. In response to this increased selective
pressure, the microbes utilize all their acquired skills
attempting to survive. Some are amazingly gifted in this
area, yet others can freely share their genetic information
with those that are totally unrelated. The end result is
that those who survive, and there are billions of them, are
now far more potent and far more resistant than when they
first arrived at the sewer plant. Most wind up in the sewer
sludge (now termed biosolids because it sounds better) which
is then applied to our farmlands.
In 2002, the National Academy of Sciences produced a major
report on the land application of sewer sludge, the solids
that are separated from the discharged wastewater. That
report admonished the U.S. EPA to look at sewage generated
antibiotic resistance. Most of this sewer sludge, classified
technically as hazardous waste, is dumped on agricultural
lands or sprayed (top-dressed) onto pasture lands. The
controls over what can be raised on this land or when the
animals can be returned are presumed to be well addressed
within the EPA regulations. Unfortunately, there is
characteristically poor compliance and the regulations are
often flaunted. Worse, in the U.S. these regulations apply
only to those spreading the sludge but not the farmer upon
whose land the material is applied----a big loophole.
Recognizing this flaw some of the major processed foods and
canned goods manufacturers in theU.S. refuse to allow
product raised on sludge applied lands to be used in their
As to the preparedness issue, sewer sludge and sewer
effluent are major transport mechanisms for disease. The
following example may help the reader appreciate all this.
In Toronto, there was a recent major out-break of SARS.
The death rates were astonishingly high and the whole of
Toronto was placed under strict public health quarantine.
The economic impact was thus devastating. Health care
workers in contact with patients died along with their
patients. The people and their movements were carefully
followed by the health authorities. The epidemic’s
quarantine was finally stopped and this was now believed to
have been premature based on business pressures against the
health authority. The health authority released statements
that all was well. The second epidemic of SARS then promptly
broke out and now people and their movements were really
SARS is transmitted by sewage and air droplets. When a
toilet is flushed, an astonishingly high level of
aerosolized material escapes, especially with the new
air-assisted toilets. No one was apparently aware of this
situation although there are several reports in the
literature discussing this.
Further, as an easily aerosolized disease organism, the
virus, once flushed entered the local sewer plants. Sewer
plants have high rates of aerosol generation. From these
plants the wastewater containing viable SARS virus was sent
to the lakes and the sludge was transported across the U.S
border to Michigan to be used on agricultural areas. No one
thought the worse of any of this, actually these pathways
were not even considered by the regulators.
Thus when engineered microbes or sewer sludge are offered
for remediation, there is a need to look to the wider
impacts from such activities. I doubt that much of this is
apparent to planning and policy-makers or elected officials.
Nonetheless, without a better perspective on how antibiotic
resistance and disease is passed around, the implications
addressed above for preparedness---or more accurately the
apparent lack of preparedness and thus public health
implications, the citizens of a community may not be being
well served. Without further knowledge, it seems it would be
reckless to continue the current situation, absent a through
analysis of how sewer plant operations or how the use of
engineered microbes may impact currently emerging infectious
diseases and antibiotic resistance.
use of compost as an absorbant
Submitted by Jacky Foo on Tue, 23/05/2006 - 06:40.
Edo McGowan wrote:
>some time ago, .....(cut)... there was some discussion of
>or incorporating sewer sludge into land where there had
>spills. While at first glance this seems like a plausible
>a process that would mix two undesirables into a viable
solution to a
>problem, it is not without side effects such as the spread
>antibiotic resistance, hence public health implications.
>Also with incorporation of engineered microbes,........
if treatment of oil contaminated soils is conducted in
compost piles with sewer sludge....
Q: would antibiotic resistant microbes and engineered
microbes die off and to what extent would it be considered
Submitted by Jacky Foo on Tue, 23/05/2006 - 07:07.
I wish to comment on the design of the experiments and
provide two suggestions for improvement.
1) I understand that you conclude that nitrogen content of
added materials play an important role in enhancing soil
microbes during the degradation of lubricating oils. I noted
that you did not sterile the mushroom spent substrate. Since
other research studies have indicated a role of Pleurotus in
degradation of oils, the use of spent substrate adds two
parameters into your experimentation:
(a) effect of nitrogen in the spent substrate
(b) effect of live Pleurotus that is found in the spent
- use sterilised mushroom spent substrate
2) if nitrogen content influences microbial activity in
contaminated soils, then an important factor is the amount
of nitrogen in the urea and spent substrate. Thus their
nitrogen content needs to be known. This will enable you to
add the same amount of nitrogen to the soil samples.
- nitrogen content in urea and sterile spent substrate
needed to be calculated or analysed.
I hope you will find these suggestions useful. Please
comment if you feel they are not important considerations in
the future design of your experiments.
degradation of chemicals
Submitted by Kenneth-Yongabi... on Sat, 27/05/2006 - 17:30.
>1) I did not see a control sample with out Pleurotus in the
>Is this needed ??
>Would soil without Pleurotus show any degradation of
Yes, there will be degradation but very slow to be
significant! Certainly, a control is obligatory!, otherwise
we could attribute changes to luck or chance!
>2) the study was done until 21 days. I wonder how long it
>for to completely degrade all the chemicals in the
>why the authors have avoided to provide such an information
This very vital missing link, it is always good to monitor
biodegradation experiment for a considerable period of time,
such studies depend on a number of factors, time,microbes
,temperature PH etc
Biodegradation in case of polycyclic hydrocarbons
Submitted by Kenneth-Yongabi... on Sat, 27/05/2006 - 17:36.
>Q: In your experimentations, did you sterilise the mushroom
>substrate before it was used ?
>Sterilisation would kill all the microbes in the spent
>enable you to avoid the addition of microbes which may
In the process of mushroom cultivation, sterilization is a
very crucial step that is unavoidable, otherwise
contaminants from the substrate would destroy your culture.
I followed the rule.
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use of compost as an absorbant
Submitted by Jacky Foo on Mon, 29/05/2006 - 09:19.
I found some info on this webpage which may interest the
Scientific research into the health threat from sewage
It contains summaries on :
* Australian study bacteria re-growth in sewage compost
* Re-growth of faecal coliforms and salmonellae in
Australian field trials
* Superbugs in sewage
* Professor Pennington on E-coli 0157
* E.coli 0157 survives and replicates in a common soil
* Reports of illnesses and deaths from residents living near
farms applying sewage sludge to their fields.
* Scientists warn that sewage spreading alters the sex of
* Scientific research into the health threat from sewage