Bacillus subtilisGene Cluster Involved in Calcium Carbonate Biomineralization

Abstract

Calcium carbonate precipitation, a widespread phenomenon among bacteria, has been investigated due to its wide range of scientific and technological implications. Nevertheless, little is known of the molecular mechanisms by which bacteria foster calcium carbonate mineralization. In our laboratory, we are studying calcite formation by Bacillus subtilis, in order to identify genes involved in the biomineralization process. A previous screening of UV mutants and of more than one thousand mutants obtained from the European B. subtilis Functional Analysis project allowed us to isolate strains altered in the precipitation phenotype. Starting from these results, we focused our attention on a cluster of five genes (lcfA, ysiA, ysiB, etfB, and etfA) called the lcfA operon. By insertional mutagenesis, mutant strains carrying each of the five genes were produced. All of them, with the exception of the strain carrying the mutated lcfA operon, were unable to form calcite crystals. By placing transcription under IPTG (isopropyl-␤-D-thiogalactopyranoside) control, the last gene, etfA, was identified as essential for the precipitation process. To verify cotranscription in the lcfA operon, reverse transcription-PCR experiments were performed and overlapping retrocotranscripts were found comprising three adjacent genes. The genes have putative functions linked to fatty acid metabolism. A link between calcium precipitation and fatty acid metabolism is suggested.

Radiocarbon Dating of Late Pleistocene Marine Shells from the Southern North Sea

“…Microbial activity is also known to induce or influence the precipitation (and dissolution) of CaCO 3 (Castanier et al 2000;Barabesi et al 2007;Decho 2010) by modification of a solution (super) saturation state (De Yoreo and Vekilov 2003;Benzerara et al 2010) and/or providing protected environments (biofilms) where carbonate can mineralize. Several authors describe that the early stage of carbonate precipitation in a biofilm is commonly characterized by the presence of nanoscale spheres (i.e.…”

Crack filling in concrete by addition of Bacillus subtilis spores – Preliminary study

“…The authors found that the B. subtilis AP91 were able to precipitate crystals of CaCO3 with the same morphology as other researches [11,[36][37][38][39][40]. Other investigators conducted the studies in the same way, first studying whether the bacterium has the ability to precipitate CaCO3 and in the sequence analyzing how that addition would behave in the cement matrix [9,41].…”

“…The precipitation of CaCO3 promoted by bacteria is classified as a Biologically Induced Mineralization (BIM) [9]. This process will result in minerals formed from three possible ways: enzymatic hydrolysis of urea, dissimilation of nitrates and aerobic metabolic conversion of calcium salts [10].…”

Bacillus subtilis fadB (ysiB) gene encodes an enoyl-CoA hydratase

“…We found an enoyl-CoA hydratase/isomerase (ECH) domain in FadB Bs through SWISS-PROT and TrEMBL database search with the Expasy ScanProsite tool. The ECH domain is also shared with the crotonase of C. acetobutylicum, encoded by the crt gene belonging to a gene cluster showing a similar organization to that of the lcfA operon (Barabesi et al 2007). Moreover, sequence alignement of the ECH domain found in FadB Bs with those of known enoyl-CoA hydratases from different sources displays significant identities with the residues known to be important for catalysis ( Fig.…”

“…Bacillus subtilis possesses a considerable number of genes, organized in five operons, that are possibly involved in the β-oxidation of fatty acids due to their similarity with corresponding E. coli genes; these are: lcfA, lcfB(yhfL), fadB Bs (ysiB), acdA, fadNAE(yusLKJ) ) and the mmgABC genes transcribed by the σ E -RNA polymerase (Bryan et al 1996). The conservation of protein sequences among different species suggested that β-oxidation plays indispensable functions under certain physiological conditions in B. subtilis, such as sporulation (González-Pastor et al 2003) as well as calcium carbonate biomineralization (Barabesi et al 2007). Among the genes products involved in fatty acids β-oxidation in B. subtilis, only FadR Bs (YsiA) has been recently characterized as a transcriptional regulatory protein, belonging to the TetR family, which negatively regulates the expression of majority of β-oxidation genes including those belonging to the lcfA operon (fadR Bs , fadB Bs , etfB, etfA, fadNAE, fadHG Bs (ykuFG), lcfB, and fadF Bs (ywjF)-acdArpoE) Matsuoka et al 2007).…”