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Fig. 4 | BMC Microbiology

Fig. 4

From: A sensitive bacterial-growth-based test reveals how intestinal Bacteroides meet their porphyrin requirement

Fig. 4

Detection threshold of heme in fecal and urine samples by measuring Bt growth stimulation. a. Two-fold heme dilutions were prepared in a feces sample (100 mg resuspended in 1 ml 0.9 % NaCl) from a healthy human adult. Fifty microliters of a feces suspension supernatant (corresponding to 5 mg feces) were loaded per well. Upper, Heme-PPIX-Screen: heme was detected in all samples, including the feces sample without added heme (as in Fig. 2a). An increase in Bt growth stimulation is detected when 64 to 128 ng heme is added to samples, indicating that this amount is distinguishable over the background amount of heme present in a healthy individual. Lower, HemoccultII® test: The same samples as in "Upper" were deposited on the HemoccultII® test and processed as per manufacturer's instructions. The HemoccultII® detection limit of heme in feces was in the range of 512-1024 ng. b. Two-fold heme dilutions were prepared in a urine sample from a healthy human donor. Upper, Heme-PPIX-Screen: Heme was detected in all spiked samples, but not in the sample lacking heme. Heme was detected at the lowest amount added, i.e., 1 ng. Lower, Siemens Multistix™ 8SG test: Urine samples as above containing the same heme concentrations were tested with the Siemens Multistix™ 8SG dipstick routinely used to test hematuria and processed as recommended by manufacturer. The lowest heme concentration detected by Siemens Multistix™ 8SG was 4-8 ng. Quantified areas of growth stimulation are shown in Additional file 2: Table S1

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