title: Genomic and enzymatic results show Bacillus cellulosilyticus uses a novel set of LPXTA carbohydrases to hydrolyze polysaccharides.
abstract: BACKGROUND
  Alkaliphilic Bacillus species are intrinsically interesting due to the bioenergetic problems posed by growth at high pH and high salt. Three alkaline cellulases have been cloned, sequenced and expressed from Bacillus cellulosilyticus N-4 (Bcell) making it an excellent target for genomic sequencing and mining of biomass-degrading enzymes.
  
  
  RESULTS
  The genome of Bcell is a single chromosome of 4.7 Mb with no plasmids present and three large phage insertions. The most unusual feature of the genome is the presence of 23 LPXTA membrane anchor proteins; 17 of these are annotated as involved in polysaccharide degradation. These two values are significantly higher than seen in any other Bacillus species. This high number of membrane anchor proteins is seen only in pathogenic gram-positive organisms such as Listeria monocytogenes or Staphylococcus aureus. Bcell also possesses four sortase D subfamily 4 enzymes that incorporate LPXTA-bearing proteins into the cell wall; three of these are closely related to each other and unique to Bcell. Cell fractionation and enzymatic assay of Bcell cultures show that the majority of polysaccharide degradation is associated with the cell wall LPXTA-enzymes, an unusual feature in gram-positive aerobes. Genomic analysis and growth studies both strongly argue against Bcell being a truly cellulolytic organism, in spite of its name. Preliminary results suggest that fungal mycelia may be the natural substrate for this organism.
  
  
  CONCLUSIONS
  Bacillus cellulosilyticus N-4, in spite of its name, does not possess any of the genes necessary for crystalline cellulose degradation, demonstrating the risk of classifying microorganisms without the benefit of genomic analysis. Bcell is the first gram-positive aerobic organism shown to use predominantly cell-bound, non-cellulosomal enzymes for polysaccharide degradation. The LPXTA-sortase system utilized by Bcell may have applications both in anchoring cellulases and other biomass-degrading enzymes to Bcell itself and in anchoring proteins other gram-positive organisms.
authors.affiliation: Lucigen Corporation, Middleton, Wisconsin, United States of America.
authors.forename: David
authors.initials: D
authors.lastname: Mead
authors.forename: Colleen
authors.initials: C
authors.lastname: Drinkwater
authors.forename: Phillip J
authors.initials: PJ
authors.lastname: Brumm
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D001407:Bacillus / Q000145:classification / Q000502:physiology*; D050260:Carbohydrate Metabolism; D005798:Genes, Bacterial; D016680:Genome, Bacterial; D023281:Genomics; D006026:Glycoside Hydrolases / Q000737:chemistry / Q000378:metabolism*; D006868:Hydrolysis; D053858:Metabolic Networks and Pathways; D008969:Molecular Sequence Data; D010802:Phylogeny; D011134:Polysaccharides / Q000378:metabolism*; D054730:Protein Interaction Domains and Motifs; D055049:Salt Tolerance
chemical_list: D011134:Polysaccharides; D006026:Glycoside Hydrolases; C019822:carbohydrase