The cell densities were adjusted to 1.0 units of optical density at 620 nm (OD620 nm) and used to determine the CSH by the CRB and SAT assays. The curli-producing E. coli
MC4 100 strain, grown on blood agar at 37 °C for 24 h, was used as a reference strain for CSH using CRB assay. BGB324 purchase L. crispatus LMG12005a Pregnant woman, vagina L. crispatus LMG 12003 L. crispatus LMG 18199 L. gasseri LMG 9203 Unknown human source L. gasseri LMG 13134 L. gasseri LMG 18177 L. johnsonii LMG 18175 Human unknown source L. rhamnosus LMG 18243a (LGG) L. rhamnosus LMG 23534 Healthy human (adult), faeces L. gasseri CCUG 44034 L. johnsonii CCUG 44519 L. reuteri DSM 20016 L. reuteri DSM 17983 Healthy human (adult), faeces E. coli MC4 100 30 °C Lineage of E. coli K-12 E. coli MC4 100 37 °C The CSH was also determined by SAT as previously described (Lindahl et al., 1981). A 10-μL aliquot of a fresh cell suspension in PBS was mixed on a glass-slide with 10 μL of ammonium click here sulphate (pH 6.8) of various molarities (0.02, 0.2, 0.8, 1.6, 3.2 and 4 M). The formation of cell aggregates was observed
after 1 min by visual reading. The molarity at which the cells caused aggregation was recorded as a positive result. CR binding was performed using CR-MRS agar (MRS with 0.01% CR, which was autoclaved separately). Washed agar- and broth-cultured cells were plated on CR-MRS agar and all plates were incubated at 37 °C for 72 h. CR-bound cells produced intense red colonies and non-CRB cells produced
colourless colonies on CR-MRS agar (Qadri et al., 1988). A quantitative CRB assay was performed as described by Qadri et al. (1988) with slight modifications for the broth- and agar-cultured cells grown at 30 and 37 °C. 4-Aminobutyrate aminotransferase Briefly, washed cell suspensions were adjusted to 1.0 units of OD620 nm and incubated with 100 μg mL−1 of CR in PBS in a total assay volume of 1 mL and incubated at 37 °C for 10 min and centrifuged at 9000 g for 30 min. The amount of dye remaining in the supernatant was quantified by measuring absorbance at OD480 nm. The concentration of CR in the supernatants was determined using the CR standard curve. From these data, CR bound by each strain was calculated using the following formula: Results were expressed as per cent CR bound. A high percentage of CR binding implies a high CSH of the strains. Escherichia coli MC4 100 was used as the reference strain for CRB assay. The effect of pH (3–8), ionic strength of the PBS (with/without 0.85% NaCl) and cholesterol (100 μg mL−1) of CRB of lactobacilli was also determined. The effect of proteinase K (100 μg mL−1, pH 8) and pronase E (100 μg mL−1, pH 8) treatment of the cells on CRB was determined by incubating 1.0 units of OD620 nm of the cell suspension with the above enzymes at 37 °C for 1 h. CRB was then determined as mentioned above after inactivating the proteolytic enzymes with 1 mM PMSF. Exponentially grown lactobacilli cells (0.