Planktonic and sessile (biofilm) growth

PLANKTONIC AND SESSILE (BIOFILM) GROWTH

Bacteria growing in liquid culture in the laboratory usually exist as individual cells or small aggregates of cells suspended in the culture medium; the term planktonic is used to describe such freely suspended cells. In recent years, however, it has become recognized that planktonic growth is not the normal situation for bacteria growing in their natural habitats. In fact, bacteria in their natural state far more commonly grow attached to a surface which, for many species, may be solid, e.g. soil particles, stone, metal or glass, or for pathogens, an epithelial surface in the body, e.g. lung or intestinal mucosa. Bacteria attached to a substrate in this way are described as sessile, and are said to exhibit the biofilm or microcolony mode of growth.