Biotransformation of various saccharides and production of exopolymeric substances by cloud-borne Bacillus sp. 3B6.

International audienceThe ability of Bacillus sp. 3B6, a bacterial strain isolated from cloudwaters, to biotransform saccharides present in the atmosphere was evaluated using in situ 1D and 2D NMR spectroscopy. Bacillus is one of the genera most frequently described in the air and in atmospheric waters. Sugars present in these environments have a biogenic origin; they include alditols, monosaccharides, disaccharides, oligosaccharides, and polysaccharides. Bacillus sp. 3B6 was able to efficiently metabolize sugars, which could thus provide sources of energy for this bacterium and allow it to live and to be metabolically active in warm clouds. In addition, a number of these saccharides (l-arabitol, d-fructose, sucrose, d-glucose, cellotetraose, cellulose, and starch) were transformed to EPSs (exopolymeric substances). We have clearly identified the structure of two EPSs as 1,6-α-galactan and partially acetylated polyethylene glycol. 1,6-α-Galactan is a newly described polymer. The production of EPSs might protect this bacterium under hostile cloud environment conditions, including low nutrient availability, cold temperature and freeze–thaw processes, UV and radical exposure, and evaporation–condensation processes and thus desiccation and osmolarity changes. EPSs could also have a potential role in atmospheric processes because they can be considered as secondary organic aerosols and efficient cloud condensation nuclei

Isolation and characterization of an extracellular glucan produced by Leuconostoc garlicum PR

White and highly viscous extracellular polysaccharide composed of D-glucose residues has been isolated from culture medium of Leuconostoc garlicum PR by acetone precipitation followed by dialysis and freeze-drying. The crude biopolymer was recovered in the yield of 50 g/L of rich culture medium and showed an apparent molecular mass over 2 x 10(7). Chemical and spectroscopic studies revealed almost linear character of the bacterial biopolymer composed of alpha-1,6-linked D-glucopyranosyl backbone carrying a low content of branched points at C-2, C-3 and C-4. Moreover, a low content (similar to 2%) of alpha-1,4-linked D-glucopyranosyl residues has been determined in the extracellular biopolymer. (C) 2010 Elsevier Ltd. All rights reserved