Enzymatic and genetic bases on assimilation, depolymerization, and transport of heteropolysaccharides in bacteria

When microorganisms utilize macromolecules for their growth, they commonly produce extracellular depolymerization enzymes and then incorporate the dep olymerized low-molecular-weight products. Assimilation of heteropolysacchar ides (gellan and xanthan) by Bacillus sp. GL1 depends on this generally acc epted mechanism. On the other hand, Sphingomonas sp. Al represents an unexp lored specific and interesting system for macromolecule assimilation. In th e presence of heteropolysaccharide (alginate), the bacterium forms a mouthl ike pit on its cell surface and directly incorporates the macromolecule usi ng a novel ATP-binding cassette transporter (ABC transporter). In this revi ew, we discuss enzymatic and genetic bases on the depolymerization and assi milation routes of heteropolysaccharides in bacteria, with particular empha sis on the novel incorporation system for macromolecules, characteristic po st-translational modification processes of polysaccharide lyases and on the mouthlike pit structure on the bacterial cell surface.