Acidothermus cellulolyticus
Classification
Higher order taxa
Bacteria; Actinobacteria; Actinobacteria (class); Actinobacteridae; Actinomycetales; Frankineae; Acidothermaceae; Acidothermus (genus)
Species
Acidothermus cellulolyticus
Acidothermus Cellulolyticus 11b, From BioEnergy Science Center(BESC)
Description and significance
Acidothermus cellulolyticus is the sole species of the genus Acidothermus , and is classified as being thermophilic , acidophilic, and cellulolytic. A. cellulolyticus was first discovered in 1986 by isolating 12 different bacterial strains collected from the upper Norris Geyser basin in Yellowstone National Park within the acidic hot springs. The 12 isolates were then tested under certain conditions including temp, pH, isolation, enrichment, antibiotic resistance, biochemical tests, and more (Winter et al. 2012) Due to it being such a new species, in 1997, 11 years after its discovery was it placed into a newly created family called acidothermaceae.
This species of A. cellulolyticus is important because it is a relatively new species being discovered and proposed in the year 1986; this gives the opportunity to test and discover new purposes for A. cellulolyticus. One of these discoveries was a new protein called HotAldO is in A. cellulolyticus , this was discovered through sharing the protein sequence from a previously discovered protein called AldO, and measuring it at temperatures above 84°C, hence the name HotAldO (Winter et al. 2012).
This species is also important because it is an efficient fast producer of the enzyme endo-1, 4-β-glucanase (E1) which is used for the commercial hydrolysis of cellulose into glucose. This whole process of enzyme production was done in transgenic rice seeds; and when done efficiently can create a bio-ethanol for the world to use as a substitute or blend with gasoline (Qing et al. 2012). Also, due to A. cellulolyticus extreme living environments it gives us the ability to clone and purify 10 xylanase (Barbote et al. 2010). This is important because it helps in the process of breaking down plant cell walls to facilitate biofuel production.
Genome structure
A. cellulolyticus has a high G=C content at ~66.9%. There are 43 different anti-codons in the genome, and 45 tRNAs representing them along with four pseudogenes. The genome encodes 2,157 predicted proteins accounting for almost 90% of the entire genome. 18 proteins show similarity to archeal proteins, and seven proteins show similarity to eukaryotic proteins (Barbote et al. 2009).
Cell structure and Metabolism
A. cellulolyticus is classified as gram negative. They are slender rods and have long slender filaments, with rounded ends. These bacteria are classified as non-motile. They however, do not have spores found within them, and thin sections in the electron microscope show no outer wall membranes are present on the cell. When colonies are formed with this microbe they will only grow on LPBM mineral salts agar. In the agar, the microbial colony has a creamy white color, a smooth circular shape, and is about 1-3 mm in diameter. '’A. cellulolyticus’’ is an autotrophic microbe. The microbe uses CO₂ fixation to create Oxaloacetate as a carbon source. Due to the fact that this microbe uses CO₂ as an organic compound this microbe is organotophic. Since A. cellulolyticus uses light as an energy source it is classified as a phototroph (Mohangheghi et al. 1986).
Ecology
Due to the fact A. cellulolyticus is acidothermic, the tolerance level is a pH of 4-6 with an optimal growth pH of 5.5. It is also a thermophile allowing it to grow in temperatures between 37°C and 70°C with an optimal growth temperature of 55°C (Ding et al. 2002). It is most closely related to the mesophilic actinobacterium Frankia.
References
[1]Barabote R.D., Parales J.V., Guo Y., Labavitch J.M., Parales R.E., Berry A.M. 2010. Xyn10A, a thermostable endoxylanase from Acidothermus cellulolyticus 11B. Applied and Environmental Microbiology 76(21) 7363-7366
[2]Barabote R.D. , Xie G, Leu D.H., Normand P., Necsulea A., Daubin V., Medigue C., Adney W.S., Xu X.S., Lapidus A., Parales R.E., Detter C., Pujic P., Bruce D., Lavire C., Challacombre J.F., Brettin T.S., Berry A.M. 2009. Complete genome of the cellulolytic thermophile Acidothermus cellulolyticus 11B provides insights into its ecophysiological and evolutionary adaptions. Genome Research 19(6):1033-1043
[3]Ding S.Y., Vinzant T. B., Adney W.S., Decker S.R., Baker J.O., Jennings E., Himmel M.E. 2002. New glycosyl hydrolases from Acidothermus cellulolyticus. National Bioenergy Center, Biotechnology for Fuels and Chemicals Division. NREL, Golden, CO 80401.
[4]Mohangheghi A., Grohmann K., Himmel M., Leighton L., Updegraff D.M. 1986. Isolation and characterization of Acidothermus cellulolyticus, a new genus of Thermophilic, Acidophlic, and Cellulolytic bacteria. USEM 36(3): 435-443.
[5]Qing Z., Wei Z., Chaotang L., Xiaoli X., Zhicheng S. 2012. Expression of an Acidothermus cellulolyticus in transgenic rice seeds. Protein Expression and Purification 82(2): 279-283
[6]Winter R.T., Heuts D.P., Rijpkema E.M., Van Bloois E., Wilma H.J., Fraaije M.W. 2012. Hot or Not? Discovery and the characterization of a thermostable Alditol oxidase from Acidothermus cellulolyticus 11B. Applied microbiology and Biotechnology 95(2): 389-403.
