Re: What bacteria or fungi cause decomposition in organic matter (leaves?)

Soil microbial communities are very complex and a wide variety of different microbes can be found in soils. In response to your question, there are innumerable microbes active in the degradation of fallen plant matter. Some of the most readily isolated microbes include species of Arthrobacter, Streptomyces, Pseudomonas, Bacillus, Penicillium, Aspergillus, and Mucor . All of these species can participate in the degradation of leaf litter.

It is important to recognize that leaf litter is actually two different kinds of food sources. There is a portion of the leaf biomass that is readily available and easily digested by most heterotrophic microbes. Such things as simple carbohydrates, proteins, and nucleic acids are easily digested by microbes. The majority of microbes in a particular spot will be in a resting state, awaiting the input of nutrients. Should a leaf fall there, the community will bloom with a burst of growth by fast-growing opportunists, termed r strategists. These will quickly eat the yummy parts of the leaf. However, there is a portion of the leaf that is very hard to digest, particularly the lignin components. We term these materials as 'recalcitrant'. These can only be digested by a limited number of organisms that have the specialized enzymes needed for their breakdown. These organisms will grow more slowly on this difficult substrate and tend to be more permanent members of the microbial community. We term these organisms K strategists. There is an interplay between between the r and K strategists. Both are good survival strategies. Given changing environmental conditions, one will dominate over the other for some time, and then as conditions change, the other will arise.

I wish that I could be more specific, but leaf litter microbial communities are very complex. We are still working at enumerating the members of these communities.

Hope this helps.

Cheers,

Mark.