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Determination of NO and CSF Levels Produced by Bacillus subtilis   

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Original research article

A brief version of this protocol appeared in:
Nature Communications
Jan 2017


The cell-to-cell communication and division of labour that occurs inside a beneficial biofilm produce significant differences in gene expression compared with the gene expression pattern of cells grew under planktonic conditions. In this sense, the levels of NO (nitric oxide) and CSF (Competence Sporulation Stimulating Factor) produced in Bacillus subtilis cultures have been measured only under planktonic growth conditions. We sought to determine whether NO and/or CSF production is affected in B. subtilis cells that develop as a biofilm. To measure the production levels of the two prolongevity molecules, we grew B. subtilis cells under planktonic and biofilm supporting condition.

Keywords: Bacillus subtilis, Planktonic growth, Biofilm, NO, CSF


NO is a key signalling molecule, playing a role in a variety of biological processes in vertebrates (Kerwin et al., 1995). C. elegans is unable to produce its own NO but is able to incorporate the NO produced by B. subtilis (Cabreiro and Gems, 2013; Gusarov et al., 2013; Kim, 2013; Clark and Hodgkin, 2014). Most organisms produce NO through aerobic conversion of L-arginine to L-citrulline in a reaction catalysed by the enzyme NO synthetase encoded by the nos gene (Sudhamsu and Crane, 2009). E. coli strains, several of which are routinely used to feed worms (OP50, HB101) (Cabreiro and Gems, 2013; Kim, 2013; Clark and Hodgkin, 2014), are not proficient in aerobic NO production because they lack a functional copy of nos (Sudhamsu and Crane, 2009). However, E. coli can produce NO under anaerobic/microaerophilic conditions by a series of biochemical reactions associated with the anaerobic respiratory chain of the bacterium (Corker and Poole, 2003). In such case, E. coli might find permissive conditions for NO production in the oxygen-depleted environment of the worm intestine. Bacteria produced-NO in worm gut that freely diffuses through the plasma membrane is oxidized to nitrate and nitrite, and thus, the concentration of nitrate and nitrite are directly proportional to the level of NO production (Gusarov et al., 2013) and can be determined using a colorimetric assay.

Intra- and interspecific quorum sensing (QS) constitutes molecules that bacteria use in nature to communicate with each other and with cells of different kingdoms (Shapiro, 1998; Ben Jacob et al., 2004; Parsek and Greenberg, 2005; Bassler and Losick, 2006). B. subtilis QS pentapeptide CSF (Competence Sporulation Stimulating Factor, also named PhrC) (Lazazzera et al., 1997) was previously reported to contribute to intestinal homeostasis by activating key survival pathways of the host (p38 MAP kinase and protein kinase B) and by inducing cytoprotective heat shock proteins (Hsps) (Fujiya et al., 2007; Willians, 2007). These effects of CSF (Willians, 2007) depend on its uptake by the protein OCTN2, a host cell membrane transporter of organic cations present in the apical face of epithelial cells (Fujiya et al., 2007). To quantify bacteria-produced CSF, promoters are commonly fused to heterologous reporter genes that encode enzymes that can be quantified using highly sensitive assays. Typically, incorporation to B. subtilis of a reporter lacZ gene, encoding β-galactosidase (β-gal) to the promoter region of a gene of interest, can be used to determine the level of CSF produced by this probiotic bacterium. When used in this manner, the Pcsf-lacZ fusion is integrated into the chromosome at the non-essential amyE locus. The basic colorimetric assay described here is the simplest and less expensive assay for quantifying β-gal activity. The cells are lysed and an aliquot of the extract is mixed with the reaction substrate, O-nitrophenyl-β-D-galactopyranoside (ONPG). When the yellow product becomes visible, the optical densities of the samples are determined spectrophotometrically.

Copyright: © 2017 The Authors; exclusive licensee Bio-protocol LLC.
How to cite: Cogliati, S., Rodriguez Ayala, F., Bauman, C., Bartolini, M., Leñini, C., Villalba, J. M., Argañaraz, F. and Grau, R. (2017). Determination of NO and CSF Levels Produced by Bacillus subtilis. Bio-protocol 7(13): e2379. DOI: 10.21769/BioProtoc.2379.

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