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

Abstract

A small (< 1 .mu.m)-filamentous, branching microorganism which was observed in Gram-stained smears of [steer] rumen microflora degraded tissues in forage samples incubated in vitro and in vivo with rumen fluid as observed by scanning and transmission electron microscopy. The microbe had prokaryotic cytoplasmic features and a gram-positive cell wall. 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.