Ultrastructure of rigid and lignified forage tissue degradation by a filamentous rumen microorganism.

A small (less than 1 mum)-filamentous, branching microorganism was observed in Gram-stained smears of the rumen microflora and was found to degrade tissues in forage samples incubated in vitro and in vivo with rumen fluid and observed by scanning and transmission electron microscopy. The microbe had prokaryotic cytoplasmic features and a gram-positive type of cell wall structure. Round to oval bodies apparently attached to hyphae resembled the sporulation pattern reported for Micromonospora. Filaments and rod and coccal forms of the microbe degraded rigid forage cell walls and lignified, thick-walled sclerenchymal cells. Location of the microbe at a slight distance from the degraded zones suggested the action of extracellular enzymes. The presence of a microbe with the capability of degrading lignified tissue represents an important and unique function in the rumen ecosystem.