[USCC] vermicompost microbiology

Boris Byzov boris.byzov at ps.msu.ru
Wed Feb 28 04:50:49 CST 2007


Dear Allison,



Thank you for recognizing my work and me.



Thinking about standardization of vermicompost properties, I mean those
microbiological parameters that correlate with its fertility and suppressive
activity. I partially agree with those people who consider presence (and
activity) of just “beneficial” and “harmful” microorganisms to be the only
useful properties to measure.



However, we need to know who are “beneficial” and who are “harmful”? With
the harmful ones is more or less clear. These are phytopathogenic fungi and
bacteria.



>From our experience, vermicomposts (just two samples we have studied)
contain high abundance of the fungus Aspergillus flavus and other A. spp.,
which are known to be phytotoxic. However, we have many other species of
fungi that are potentially harmful. Using luminescent microscope, we found
around 1000000 spores/g (!) of fungi in vermicompost (45% moisture) made of
cow manure, but practically no mycelium. Who are they? What will happen to
these spores when they come to soil?



To isolate and identify them sometimes we need specific methods and
experience. Here we can use both dilution plate and molecular methods. The
latter I think is more preferable, but requires equipment and experience of
the personal. Using molecular technique, we can follow the population
dynamics of those microorganisms that are potentially important for
vermicomposts.



Beneficial microorganisms are much less clear. Growth promoting or
antagonistic microbes? How can we follow them?



Again form our experience, vermicomposting process promotes actinomycetes to
grow. Spores of some actinomycetes can proliferate during passage through
the earthworm digestive tract (our works in 90ths). We found more
actinomycete mycelium in vermicasts comparing to excrement and in
vermicompost vs. food substrate (Byzov et al., 1995). Actinomycetes are
known as producers of antibiotics. May be this is an important parameter?



Therefore, we need to find a set of such SOIL microorganisms that could be
indicators of bad and good quality of vermicomposts. May be some of them can
be eliminated or introduced to compost to improve its quality. But, it is a
labor and time-consuming work.



Integral parameters (which are easier to measure) such as BIOLOG, Degens,
Harris’ catabolic diversity and others, could be useful too, but we have to
find how they correlate with the quality of product.



Regards,



Boris



This is a great topic, thanks so much for bringing it up. I'm familiar with
Dr. Byzov's work and have enjoyed reading his papers :-).

Before we think about standardization and evaluation, we need to know what
properties we want in a vermicompost. Do we want to optimize plant growth
promotion, and/ or plant disease suppression? Finding out and measuring
what makes a good vermicompost totally depends on how we want to use it and
how we want it to perform.

I work with vermicompost and the suppression on Pythium damping off in
order to understand how disease suppression works. I'm of the opinion that
until we understand how it works, we will be forever shooting in the dark
when it comes to using microbial community measurements to predict what
properties a vermicompost will have. I have read literally hundreds of
papers that have attempted to find predictive factors for compost and
vermicompost disease suppression with mixed success. But if one paper finds
a measurement that does correlate with suppression you will be sure that
another paper will find that same measurement does not correlate with
suppression. We are dealing with an enormous black box. Science's current
understanding of soil microbiology is growing every day, but there is still
so much basic research that needs to be done in order to understand these
more applied questions. Even if two vermicompost samples have the same
total microbial activity, the species composition and function of the
communities can be completely different. For instance I am working with two
cow manure vermicomposts. One suppresses Pythium and the other doesn't.
Why? I don't know yet. I'll let you know when I find out :-).

During my M.S. in Soil Science at Cornell University I used molecular
community profiling techniques (Denaturing Gradient Gel Electrophoresis
DGGE and Terminal Fragment Length Polymorphism T-RFLP) to look at changes
in bacterial community composition during vermicomposting and thermophilic
composting. There was only a 55% species similarity between the different
types of compost made from the same cow manure feedstock. So again, broad
total community activity measurements do not capture these subtle but
hugely important differences. The total microbial activity and cell number
can be similar, but the actual species that make up the community are
totally different. During two years of field trials we found that the
different types of compost significantly affected the bacterial communities
associated with tomato roots. These differences in rhizosphere community
composition persisted even when tomato plants were transplanted into the
field and may have affected overall yield and growth. This manuscript is
still in preparation, but I will let the list know when it comes out.

I look forward to hearing more on this topic,
Allison

Some great recent papers on vermicompost microbiology:

Aira, M., F. Monroy, and J. Dominguez (2006) C to N ratio strongly affects
population structure of Eisenia fetida in vermicomposting systems. European
Journal of Soil Biology, 42: p. S127-S131.

Anastasi, A., G.C. Varese, S. Voyron, S. Scannerini, and V.F. Marchisio
(2004) Characterization of fungal biodiversity in compost and vermicompost.
Compost Science & Utilization, 12(2): p. 185-191.

Anastasi, A., G.C. Varese, and V.F. Marchisio (2005) Isolation and
identification of fungal communities in compost and vermicompost.
Mycologia, 97(1): p. 33-44.

Fracchia, L., A.B. Dohrmann, M.G. Martinotti, and C.C. Tebbe (2006)
Bacterial diversity in a finished compost and vermicompost: differences
revealed by cultivation-independent analyses of PCR-amplified 16S rRNA
genes. Applied Microbiology and Biotechnology, 71(6): p. 942-952.


Some older papers on earthworm digestion and its' effects on the microbial
community that I have found helpful (and that you might already be familiar
with):

Scheu, S. (1987) Microbial activity and nutrient dynamics in earthworm
casts (Lumbricidae). Biology and Fertility of Soils, 5: p. 230-234.

Pedersen, J.C. and N.B. Hendriksen (1993) Effect of passage through the
intestinal tract of detritivore earthworms (Lumbricus spp.) on the number
of selected Gram-negative and total bacteria. Biology and Fertility of
Soils, 16: p. 227-232.

Hartenstein, F., E. Hartenstein, and R. Hartenstein (1981) Gut load and
transit time in the earthworm Eisenia foetida. Pedobiologia, 22: p. 5-20.

Tiunov, A.V. and S. Scheu (2000) Microfungal communities in soil, litter
and casts of Lumbricus terrestris L. (Lumbricidae): a laboratory
experiment. Applied Soil Ecology, 14(1): p. 17-26.

Lavelle, P., C. Lattaud, D. Trigo, and I. Barois (1995) Mutualism and
biodiversity in soils. Plant and Soil, 170(1): p. 23-33.

Trigo, D., I. Barois, M.H. Garvin, E. Huerta, S. Irisson, and P. Lavelle
(1999) Mutualism between earthworms and soil microflora. Pedobiologia,
43(6): p. 866-873.

Brown, G.G. (1995) How do earthworms affect microfloral and faunal
community diversity? Plant and Soil, 170: p. 209-231.

Brown, G.G., I. Barois, and P. Lavelle (2000) Regulation of soil organic
matter dynamics and microbial activity in the drilosphere and the role of
interactions with other edaphic functional domains. European Journal of
Soil Biology, 36(3-4): p. 177-198.


****************************************************************************
**********
Allison L H Jack
Graduate Student
Department of Plant Pathology
Cornell University
335 Plant Science
Ithaca, NY 14850
607.273.5762


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> Today's Topics:
>
>    1. Compost microbiology (Allison L H Jack)
>    2. Vermicompost microbiology (Allison L H Jack)
>    3. Compost and Global Warming: Curbside Yardwaste Collection may
>       not reduce Global Warming (David Goldstein)
>


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