[USCC] Vermicompost microbiology

[Allison L H Jack]

Dr. Byzov and Mr. Yakushev wrote:

We are involved in a vermicomposting project aiming at development of 
microbiological criteria of vermicomposting process and evaluation of 
vermicompost products. As far as I know, there are only few studies, which 
address microbiological aspects of vermicomposting, and to date no approach 
exists to evaluate quality of vermicomposts that are made from many 
different organic wastes, except for pathogenic microorganisms and 
nematodes. However, it is important for development standards for 
vermicomposting.

To my opinion, an earthworm should somehow unify microbial community of 
organic waste under passage through the gut. There are few studies on this 
topic. Our approach is to study integral parameters of microbiol activity, 
like multisubstrate utilization profile, enzymatic activities, etc.

If you have any comments, on what should we measure (bacterial and fungal 
biomass, ratio total/active biomass, respiration, catabolic diversity, etc) 
and how can we standardize microbial properties of the vermicomposting 
products.

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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.


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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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