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[compost_tea] compost tea, E.coli and NOP



Good Morning Fellow Compost tea enthusiasts. Just a note of 
introduction. I'm Joel Reiten, Seed Production Manager for Bejo Seed 
Company. I am responsible for the conventional as well as organic 
seed production for our company in the US. I have been involved in 
compost teas for around 7 years now and have met many of you and hope 
to meet the rest of you in the future.  I'm definitely a lurker at 
this site as I am at many during the growing season. Now that I have 
had a chance to review some of the messages on the different compost 
and compost tea websites I am somewhat  angered and very disappointed 
at some of the comments and the one sided miss ?information that 
seems to permeate some of the messages. This response was spurred on 
by two organic growers that I work with who forwarded me some of the 
e-mails for comment. And no, as some of you might wonder later, 
neither grower is connected with Growing Solutions Inc or BBC Labs. 

I do not hold an advanced degree in microbiology, my education is in 
animal science and genetics, but it is my job to know all of the 
facts (or opinion) of experts that work in the fields of 
microbiology, and as of late industrial fermentation. I grapple with 
the status of a study, that has not been published in a peer reviewed 
publication or run thru the academia statistics mill and make the 
decision on how much is fact and how much is opinion. So what I am 
going to say here is my opinion based on what I consider fact. 

First let's talk about the study that Vickie Bess (I'll leave the Ms. 
Out) and her staff did at BBC Labs. How many of you actually read the 
entire paper? I thought the paper was pretty thought provoking and 
did show what microbiology textbooks and industrial fermentation 
experts will tell you. E coli can live and grow in an aerobic 
environment and that it prefers a simple sugar nutrient source. It 
also indicated what may happen in a mixed microbe culture loaded with 
simple carbon sources.

The accusation that the study used un-composted material is 
unfounded. The facts that I have are that the compost in question 
went thru the complete composting regime and was tested before sale. 
The tests turned out positive for E. coli and the compost was not 
sold as compost. The assertion that properly made compost will not 
contain E. coli is also unfounded. The composting process is a 
sanitizing process not a sterilization process and unless you produce 
your compost in an enclosed environment there is always a chance for 
contamination. 

How about the oxygen levels reported in the study. Again a lot on 
conflicting information. Are the oxygen levels that were reported by 
BBC labs possible? Yes, without question. The graphs and charts from 
the USGS have been cited as the highest possible levels of oxygen 
that can be held in water at a certain temperature and pressure. 
Without getting too technical I'm going to say that this is true, but 
only to a point. These numbers would be considered the high end 
of "normal" like a healthy lake. Numbers that are higher than those 
from the USGA chart are considered super saturated. Be careful with 
this word. Just because water is supersaturated does not mean it will 
oxidize organic compounds. It simply means that it is carrying more 
oxygen than would be normal for water at that temp and pressure. 
Without question water that is carrying extremely high levels of 
oxygen are harmful to aquatic life and microbiology but super 
saturation in of its self does not equal harmful conditions. 

The oxygen transfer from air to liquid is primarily affected by the 
interfacial area of the gas bubble. Increasing the interfacial area 
can increase the oxygen transfer rate into the fluid. Increasing the 
interfacial area can be accomplished by increasing the aeration rate 
and decreasing the bubble size. The fine bubble diffuser plates that 
Growing Solutions uses in its brewers is extremely good at producing 
very small bubbles at various rates of air flow. The factors that 
affect how much oxygen can be "forced" into the water is based on the 
amount of pure O2 in the air as well as the pressure that the air is 
under. This pressure effect does not mean that the entire vessel 
needs to be pressurized; it can simply mean the hydrostatic pressure 
at the base of a column of liquid. Combining all of these factors 
together these numbers are well within limits. I also had a 
biochemical engineering collaborator look at the oxygen transfer rate 
as well as roughly calculate the steady state relationship between 
oxygen uptake and oxygen transfer based on a high population of 
respirating bacteria growing in a simple sugar based liquid medium. 
Based on the air diffusion plates used in the System 25 at the time 
of the tests and assuming that all of the equipment was working 
within manufactures specs, anaerobic conditions very likely did not 
occur and the high oxygen levels were within reason.

Other BBC lab thoughts.  Plate counts vs. direct counts. BBC Labs 
uses the plate count method of evaluating soil and tea microbes. You 
can go to their site to read about their different classifications. 
I'm not going to debate the usefulness of one over the other but I do 
feel that plate counts have their place. You can pick up any good 
microbiology text and find a long list of usefulness and short 
comings of both methods. Check out Brock  Biology of Microorganisms 
9th Ed., M.T. Madigan, J.M. Martinko, J. Parker, (2000) Prentice-
Hall, New Jersey. 

The problem with direct counts is that you are counting lots of cells 
but you are not really sure what they are for the most part. They can 
be good bugs or bad bugs. I am very hesitant with direct counts for 
tea brewers because the microorganisms have been exposed to a medium 
that is greatly different than they would experience in the soil. The 
liquid environment in a brewer, loaded with many times the simple 
sugars that are found in soils, is bound to shift the populations of 
microbes. Plate counts use soil extract agar or artificial media that 
closely mimic the amino acids, growth factors and other chemicals 
found in the soil, but it is also very low in simple carbon sources, 
as is usually the case in soils, so the growth of the microbes on the 
culture media is slow and the colony size is small. The conditions 
that the media is cultured at will influence the outcome to some 
extent, but think of the wide range of environmental conditions that 
exist in the soil profile over the seasons. It's impossible to 
culture for all conditions and the conditions in a brewer hardly 
mimic the conditions in soil.

  A legitimate question with plate counts is that the number of 
microbes counted is usually lower than in direct counts. Is this 
difference in numbers dead cells or cells that are non-culturable? 
But both methods are based on dilutions and the numbers can be 
mathematically calculated to represent true numbers in the soil or 
tea. I personally feel that in a short time newer methods like enzyme 
reaction analysis or DNA probes will allow us to come up with more 
accurate numbers and will allow us to come up with a better idea of 
true diversity in a natural environment. I also personally feel that 
in a situation where I am working with biologically healthy soils 
that plate counts are more useful to me because I am trying to gently 
coax soil microbe populations in a certain direction and I need to 
know if I am doing so down to the genus and species. 

There has also been the assertion that the species richness diversity 
index (SRD) that BBC Labs uses is incorrect and does not exist in the 
literature. First of all an index is a way to reference the 
relationship between sets of data, like species richness and species 
diversity. There are lots of examples of such indexes in published 
ecological research and well as a number of software programs to 
calculate these indices. An oldie but a goodie is the Simpson's 
Index, Simpson, E.H. 1949. Measurement of diversity. Nature 163:688. 
Since 1949 this index has been broken down and defined in several 
ways but is an index of species richness and diversity. An index that 
I am working with is the Shannon-Wiener index. This index shows a 
relationship to species richness and diversity but it measures the 
order, or disorder, observed within a particular system. If you want 
to delve into the math it is also easy to see how negative numbers 
can come into play if the population falls below a set level. I am 
not privy to the math behind BBC Labs methods of calculating their 
SRD numbers but I believe that they have a factual basis and can be 
related to the soil food web. Other references are Peet, R.K. 1974. 
The measurement of species diversity. Annual. Rev. Ecol. Syst. 5:285-
307. and Krebs, C.J, 1989. Ecological methodology. Harper and Row, 
NY. 

Thoughts on Brewers.

Great discussion about types of brewers in this group. The bottom 
line is that there are lots of brewers available or you can build 
your own depending on your situation. The technology behind the 
aeration of water and the culture of microbes in a liquid solution is 
well documented and not rocket science. The exact science behind the 
culture of extremely diverse microbes from their extraction to their 
growth and development is however a bit more tricky. I'm not sure how 
comfortable I am with trying to culture both bacteria and fungi at 
the same time in the same container. They have different growth rates 
and different nutrient requirements that include growth agents that 
may not be in the same amounts or ratios in compost than they are in 
the soil. Mixed populations also tend to excrete toxins that if not 
monitored and removed can affect the population diversity with a 
brewer.

 Let me stress however that if you use good quality compost and if 
you have a vigorous enough activity within the vessel, you will sheer 
the microbes out of the compost and get them into solution and you 
will get good numbers both by direct counts and by plate counts of 
all of the components of a good soil food web. If you are using 
compost teas on biologically inactive soils or in soils that have 
been chemically abused you will more often than not get good results. 
If however you want to use compost teas for a more specific reason 
then I think you need to know a bit more about the specific types of 
organisms that you want to culture and how to encourage their growth.

Brewing nutrients. 

This discussion could go on for days. I'll be at the Eco-Farm 
conference and will talk about nutrients in teas but here is a 
summary. I do not think that the addition of large (disproportionate) 
amounts of simple sugars as carbon sources are the correct way to 
brew good ( highly diverse populations that mimic the natural soil 
populations) compost teas. If you look at the carbon sources in the 
soil they include amino acids, organic acids, pentoses, hexoses, 
pyrimidines, puridines, vitamins and many other organic enzymes and 
growth factors. High levels of simple sugars give preferential 
treatment to some bacteria and a few fungi to the detriment or 
exclusion of others. After a great deal of research I prefer Growing 
Solutions catalyst food source because it has very low levels of 
simple sugars and its very diverse level of more complex carbon 
sources and growth factors that result in a tea that is more 
representative of the microbes in a natural soil food web. Is this 
good enough? No, I think that much more work needs to be done on food 
sources as well as buffering agents, paying attention to osmotic 
conditions and perhaps running our brewers on a more continuous basis 
rather than as a batch culture.

Biofilms. I saw a post that stated that biofilms were a sign of 
anaerobic activity. This is a new one on me. You can find biofilms on 
nearly all surfaces that are exposed to a biologically active liquid, 
aerobic or anaerobic. Bio-films are not difficult to remove if you 
get to them before they dry. Biofilms make great glues!

E-coli and the NOP. I left these comments until last knowing that a 
few diehards would slog thru this long post. E. coli and the question 
of food safety is a hot button topic at the present time. I'm 
certainly not going to downplay the significance of the danger of E. 
coli O157:H7 if ingested. But I do believe that the danger has been 
blown a bit out of proportion particularly when it comes to compost 
teas. 

Let's look at the facts. Physiologically E. coli is versatile and can 
adapt too many environmental habitats. It can grow on media with 
glucose as the sole organic ingredient. Wild-type E. coli has no 
growth factor requirements and can metabolically transform glucose 
into all of the macromolecular components that it needs. The 
bacterium can be grown in the presence or the absence of O2. Under 
anaerobic conditions it will grow by means of fermentation but in 
aerobic conditions it has the ability to switch to an alternate form 
of respiration that utilizes NO3 and NO2 for its respiratory electron 
transport processes. In part this is why E. coli can adapt to 
anaerobic (intestinal) or aerobic (surface contact) conditions. 

I can find no references where it has been demonstrated that in a 
mixed culture E. coli is eliminated by other microbes. I do agree 
however that E. coli growth can be reduced to nearly 0 if its food 
source is reduced and if the mixture contains high levels of a 
diverse population of other microbes.

I believe the course of action for the NOP is straightforward. 

1.	Use properly prepared compost for application as a solid or 
as a liquid such as compost tea.

2.	No raw manures within 120 days of harvest.

3.	Compost or compost teas used within 120 days of harvest must 
have a documented negative E. coli test.

With the availability of rapid E.coli tests that the water treatment 
field uses, these tests can be included in the organic
 farm management plan and part of the inspection can include a 
demonstration that the farmer knows how to use the tests.

The future of compost teas is very exciting. I will continue to use 
compost teas as an important part of my organic farm management.  
Much work needs to be done to continue to bring the use of compost 
teas into the fold of truly useful techniques that the organic and 
conventional farmer and horticulturists can use to build healthy 
soils and combat plant diseases. To this end the divisiveness of 
ridiculing a person or a business because they do not conform to one 
persons ideals is detrimental to the openness and continued 
advancement of this young and growing industry.

PS The paper describing my work with compost teas for the control of 
Xanthomonas is now ready. You can request a copy or you can read it 
in the OR Tilth paper next month.

All the Best,

Joel





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