Cellulomonas

Cellulomonas
Systematics
Domain :	Bacteria (bacteria)
Department :	Actinobacteria
Order :	Actinomycetales
Subordination :	Micrococcineae
Family :	Cellulomonadaceae
Genre :	Cellulomonas
Scientific name
	Cellulomonas
	Bergey et al. 1923
species
	Cellulomonas biazotea; Cellulomonas bogoriensis; Cellulomonas cartae; Cellulomonas cellasea; Cellulomonas cellulans; Cellulomonas denverensis; Cellulomonas fermentans; Cellulomonas fimi; Cellulomonas flavigena; Cellulomonas gelida; Cellulomonas hominis; Cellulomonas hominilata; Cellulomonas iranensis; Cellulomonas persica; Cellulomonas terrae; Cellulomonas turbata; Cellulomonas uda; Cellulomonas xylanilytica;

Cellulomonas is a genus of rod-shaped, aerobic or facultative anaerobic soil bacteria with a chemoorganotrophic metabolism ( chemoorganotrophy ). They are catalase- positive and arecounted amongthe gram-positive bacteria, but are still easy to decolorize. Cellulomonas cultures are usually opaque, pigmented yellow and convex. The locomotion occurs through one or more flagella . The most important habitats are the soil and decomposed plant material. Optimal growth takes place at a temperature of 30 ° C and a pH value between 9 and 10.

Taxonomy

As early as 1923, the genus Cellulomonas was discovered by David H. Bergey et al. first described as gram-negative bacteria . It later turned out that they are gram-positive, but very easily decolorized. To date, 18 different species of this genus are known, of which Ce. flavigena represents the type species that the JGI (Joint Genome Institute) has completely sequenced. The genome contains 3785 genes. DNA-DNA hybridization studies and investigations of the ribosomal 16S rRNA showed that the genus Oerskovia can also be counted as part of Cellulomonas .

metabolism

Cellulomonas have either an oxidative or fermentative metabolism. Most species produce acid from glucose , maltose , sucrose , xylose and lactose , both aerobically and anaerobically . Cellulomonas is able to hydrolyze cellulose (through cellulase ), starch and gelatin . They also reduce nitrate to nitrite and produce DNases .

Cellulose decomposition

Cellulose molecules are chains of glucose molecules . The basic unit is the disaccharide cellobiose . Cellulose consists of the amorphous (disordered) and the crystalline (ordered) area.

Cellulases decompose ( hydrolyze ) the bonds of the cellobiose. They are connected to the cell surface of Cellulomonas so that the soluble breakdown products can be quickly absorbed. In order to obtain the largest possible reaction surface, the bacteria accumulate with their longitudinal body axis parallel to the cellulose fibril.

There are two different basic types of cellulases: one enzyme complex is firmly attached to the bacterium, while the other is free in the extracellular space. Cellulomonas flavigena uses both methods.

Cellulases form a whole family of enzymes:

Endoglucanases first split the amorphous water-accessible areas of the cellulose.

Exoglucanases then separate the exposed ends from the non-reducing end into tri- and disaccharide units .

Finally, cellobiases dissolve the cellobioses into their individual glucose molecules.

Cellobiose and glucose are ultimately absorbed into the cell.

The absorbed disaccharides can then be broken down by the cellobiose phosphorylase without the need for ATP:

Cellobiose + phosphate → glucose-1-phosphate + glucose

Hemicellulose decomposition

Hemicellulose is an alkali-soluble polysaccharide and consists of three main sugar components ( xylans , mannans , galactans ), as well as numerous side groups such as acetyl ester , methyl ether and uronic acid . In contrast to cellulose, instead of hexose β-D-glucose is pentose β-D- xylose , in which the C6 group is replaced by an H atom.

Hemicellulose is more easily degradable and water-soluble than cellulose because it forms shorter chains, is branched and not crystalline. The main component is made up of xylans, which can be broken down by xylanases . Other enzymes are required to split off the side groups. The main degradation products are β-D-xylolose and the disaccharide xylobiose.

Illustrations

DOE, Joint Genome Institute (February 13, 2011 6:00 p.m.)
Cellulomonas aerilata sp. nov., isolated from an air sample (February 14, 2011 9:42 am)
Simon Bálint: Evaluation of solid raw materials from the biological treatment of biomass . (PDF; 682 kB) p. 20, February 13, 2011

literature

David Hendricks Bergey, John G. Holt: Bergey's manual of determinative bacteriology . 1994, ISBN 0-683-00603-7 , p. 575
Washington C. Winn, Elmer W. Koneman: Koneman's color atlas and textbook of diagnostic microbiology . 2006, ISBN 0-7817-3014-7 , p. 826
Ernst-Detlef Schulze, Harold A. Mooney: Biodiversity and ecosystem function . 1994, ISBN 3-540-58103-0 , p. 76
Hans Günther Schlegel, Georg Fuchs: General microbiology . 2006, ISBN 3-13-444608-1 , p. 289