Correction: Spatial organization of Pseudomonas aeruginosa biofilms probed by combined matrix-assisted laser desorption ionization mass spectrometry and confocal Raman microscopy

Abstract

Correction for 'Spatial organization of Pseudomonas aeruginosa biofilms probed by combined matrixassisted laser desorption ionization mass spectrometry and confocal Raman microscopy' by Rachel N. Masyuko et al., Analyst, 2014, DOI: 10.1039 In the original study for the DOI detailed above, Masyuko et al. examined the Raman and mass spectrometric microspectra and images accompanying transition from planktonic cells to biolms in wild-type Pseudomonas aeruginosa and in a quorum sensing (QS)-decient mutant, DlasIDrhlI. In the course of follow-up studies, we became aware that some of the Raman spectra attributed to wild-type biolm could have arisen from a contaminant, microparticulate polystyrene (PS). Subsequently, a new series of wild-type Pseudomonas biolms were grown under rigorously PS-free conditions, and new spectra and images were acquired. For the new data shown in the gures below, Fig. 1 replaces the spectrum shown in Fig. 1(b) of the original and Fig. 3 replaces the images shown in Figs. 3(b) and S2 of the original. A detailed consideration of the bands and their assignments in the new biolm spectrum is given in the Supplemental Information (see below).While detailed analysis of the biolm spectrum, Fig. 1(b), and the image acquired, Fig. 3(b), differ from the corresponding data in the original, the major conclusions of the paper are unaffected. In particular:(1) the wild-type biolm spectra are markedly different than the corresponding wild-type planktonic cell spectra, cf. Fig. 1(b) vs. Fig. 1(a);(2) wild-type biolms produce spectra that are characteristic of rhamnolipids, secreted as part of the biolm formation process, and by a co-secreted protein/peptide component; and(3) these data are consistent with the formation of a thick (relative to the sampling depth of the CRM) biolm aer 72 h in the wild type cells, but not in the QS mutant. Supplemental InformationText in the original describing the Raman spectra ( Figs. 1(b) and 3(b) in the original) should be replaced with the following.Upon biolm formation, dramatic changes occur in the spectrum, Fig. 1(b). Biolms cultivated on bare Si exhibit a greatly reduced SiO 2 background (915-1015 cm À1 ), presumably because biolms at 72 h are much thicker than the <1 mm confocal depth of the CRM. In addition, the strong DNA/RNA-related bands at 747 (thymine), 1126 (cytosine), and 1310 cm À1 (adenine) are all diminished in relative intensity. The strong band at 1585 cm À1 is reduced in strength and a new band at 1606 cm À1 grows in. In addition, narrow bands with peaks centered at 1005 cm À1 and 1034 cm À1 appear as well as bands centered at 830 cm À1 , 1166 cm À1 , 1186 cm À1 , 1417 cm À1 , 1445 cm À1 and 1558 cm À1 . Most striking is the intense peak at 1005 cm À1 attributed to symmetric ring breathing vibrations in phenylalanine and tryptophan, indicative of proteins. 1 Other bands characteristic of proteins are at 830 cm À1 ring breathing vibrations in tyrosine (with a possible contribution from rhamnolipid), 1186 cm À1 arising from C-H in plane bend...