The growth of marine Pseudomonas sp. NCIMB 2021 as continuous cultures in the presence of surfaces of AlSl 316 stainless steel allowed the isolation and partial chemical characterization of exopolymers released into the culture medium (free exopolymers), as well as capsular and biofilm exopolymers. Fourier-transform infrared (FTIR) spectroscopy demonstrated the presence of 0-and N-acetylation within the carbohydrate moieties and a predominant 3,,-helical structure of the protein component, highly resistant to hydrogeddeuterium exchange. Differences between the exopolymers were apparent. Relatively less uronic acid residues were detected in the capsular exopolymers compared to either the biofilm or free exopolymers. 0-and Nacetylation were greatest in the biof ilm exopolymer. SDS-PAGE protein profiles confirmed differences between exopolymers. The secondary structures of proteins determined using FTIR spectroscopy indicated that the capsular exopolymer had reduced helical content and an increased aggregated strand content compared to the biofilm exopolymer. However, the free exopolymer had an increased P-sheet component and a reduced unordered component when compared to the biofilm and capsular exopolymers. These data suggest that exopolymer chemistry varies with cellular mode of growth.

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Polysaccharide production by streptococci from sucrose or raffinose has generally been examined by one of two methods-streak or pour plates containing carbohydrate and incubated under air or broth cultures containing the carbohydrate. In the former method polysaccharide production is accompanied by the development of large, confluent moist colonies, usually slimy in appearance. With the latter method, polysaccharide formation is accompanied by an increased viscosity of the broth, sometimes to the point of solidification. Niven et al. (1941a) and Sherman et al. (1943) showed that all cultures of Streptococcus salivarius in their collection produced a polysaccharide on agar and in broth media. Of a considerable nuimber of other streptococci representative of Lancefield's Groups A through H, and members of Sherman's lactic, enterococcus and viridans divisions, only 1 culture of a collection of 54 strains of Streptococcwu bovis showed typical slime production on sucrose agar. Niven et al. (1941b) identified this material as a dextran. In a later publication, Niven et al. (1946) showed polysaccharide production both on agar and in broth by 7 additional strains of S. bovis, and to a lesser extent by Streptococcus s.b.e. (Streptococcus