Pseudomonas fluorescens subsp. cellulosa: an alternative model for bacterial cellulase.
Pseudomonas fluorescens subsp. cellulosa, a Gram-negative soil bacterium, can utilize crystalline cellulose or xylan as main sources of carbon and energy. Synthesis of endoglucanases and xylanases is induced by Avicel, filter paper, carboxymethylcellulose or xylan and is repressed by cellobiose, glucose or xylose. These enzymes are secreted into the culture supernatant fluid and do not form aggregates or associate with the cell surface. Cells of Ps. fluorescens subsp. cellulosa do not adhere to cellulose. In cultures containing Avicel or filter paper, a significant proportion of the secreted cellulase and xylanase activities becomes tightly bound to the insoluble cellulose. Western blotting has revealed that endoglucanase B, xylanase A and a cellodextrinase encoded by genes previously isolated from Ps. fluorescens subsp. cellulosa and expressed in Escherichia coli, are synthesized by the pseudomonad under a variety of conditions. These enzymes appear to be post-translationally modified, probably through glycosylation. Overall, it appears that the cellulase/hemicellulase system of Ps. fluorescens subsp. cellulosa differs from the model established for celluloytic anaerobes such as Clostridium thermocellum.
Hazlewood
G P
GP
Department of Biochemistry, AFRC Institute of Animal Physiology & Genetics Research, Babraham, Cambridge, UK.
Laurie
J I
JI
Ferreira
L M
LM
Gilbert
H J
HJ
D015153:Blotting, Western; D002480:Cellulase / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D002482:Cellulose / Q000378:metabolism; D005591:Chemical Fractionation; D002850:Chromatography, Gel; D043364:Endo-1,4-beta Xylanases; D006026:Glycoside Hydrolases / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011551:Pseudomonas fluorescens / Q000201:enzymology* / Q000235:genetics; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000378:metabolism; D012988:Soil Microbiology
D011994:Recombinant Proteins; D002482:Cellulose; D006026:Glycoside Hydrolases; C023305:hemicellulase; D002480:Cellulase; D043364:Endo-1,4-beta Xylanases