Spectroscopic characterization of cell membranes and their constituents ofthe plant-associated soil bacterium Azospirillum brasilense

Structural and compositional features of bacterial membranes and some of th eir isolated constituents (cell surface lipopolysaccharide, phospholipids) of the plant-growth-promoting diazotrophic rhizobacterium Azospirillum bras ilense (wild-type strain Sp245) were characterized using Fourier transform infrared (FTIR) spectroscopy and some other techniques. FTIR spectra of the cell membranes were shown to comprise the main vibration modes of the rele vant lipopolysaccharide and protein components which are believed to be inv olved in associative plant-bacterium interactions, as well as of phospholip id constituents. The role and functions of metal cations in the structural organization and physicochemical properties of bacterial cell membranes are also discussed considering their accumulation in the membranes from the cu lture medium. (C) 1999 Elsevier Science B.V. All rights reserved.