Colorimetric dimethyl sulfide sensor using Rhodovulum sulfidophilum cells based on intrinsic pigment conversion by CrtA

Abstract

A colorimetric whole-cell sensor for dimethyl sulfide (DMS) was constructed based on the in vivo conversion of intrinsic pigments in response to the analyte. In a marine bacterium, Rhodovulum sulfidophilum, carotenoids are synthesized via the spheroidene pathway. In this pathway, demethylspheroidene, a yellow carotenoid, is converted to spheroidene under catalysis of O-methyltransferase. Spheroidene monooxygenase (CrtA) catalyzes the terminal step of the pathway and converts spheroidene to spheroidenone, a red carotenoid. Here, the CrtA gene in R. sulfidophilum was removed and then reintroduced downstream of the DMS dehydrogenase gene promoter. Using this whole-cell sensor, 3 muM DMS or dimethyl sulfoxide can be detected without adding any color-forming reagent. The ratio of the red spheroidenone to total carotenoids increased, as the DMS concentration was raised to 0.3 mM. Comparison of the signal to the background color indicated a shift in the color coordinate from a yellow to a red hue. An intense signal was obtained with 1-day incubation at a high cell density when sensor cells at the exponential growth phase were used. These results show that the genetically engineered R. sulfidophilum cells can be used to monitor the quality of marine aquacultural environments by the naked eye.

Pigment-based whole-cell biosensor system for cadmium detection using genetically engineered Deinococcus radiodurans

“…To overcome these drawbacks, bacterial whole-cell biosensors using natural pigment as the biosensor output have been reported. A red pigment biosynthetic gene (crtA) of Rhodovulum sulfidophilum was used for arsenite and dimethyl sulfide detection [23,24]. A bluegreen pigment synthesis of Pseudomonas aeruginosa was used for N-butyryl homoserine lactone detection [22].…”

Novel Carotenoid-Based Biosensor for Simple Visual Detection of Arsenite: Characterization and Preliminary Evaluation for Environmental Application

“…The bacterial color change in crtIBS was stable under both anaerobic and aerobic preculture conditions. In contrast, the bacterial color change in crtA-based biosensors is very sensitive to dissolved oxygen in the culture medium (14). Therefore, our findings demonstrate that crtIBS could be used for water samples containing various oxygen concentrations.…”

“…We recently reported that a carotenoid biosynthesis gene, crtA, can also be used as a novel reporter in whole-cell biosensors made from Rhodovulum sulfidophilum (9,14). Two crtAbased biosensors have been established by disrupting the crtA gene and reintroducing it downstream of a DNA response element.…”

“…Because R. sulfidophilum is a marine bacterium, an adequate concentration of salt needs to be added in order to analyze groundwater samples. Furthermore, because CrtA requires molecular oxygen to form 2-keto carotenoids (36), the bacterial color change is very sensitive to the amount of dissolved oxygen in the culture medium (14).…”

Sposensor: A Whole-Bacterial Biosensor That Uses Immobilized <i>Bacillus subtilis</i> Spores and a One-Step Incubation/Detection Process

“…Reporter genes encoding enzymes, enzymatic complexes or fluorescent proteins have been used to construct whole-cell biosensors such as ␤ -galactosidase, the wellknown protein reporter for which numerous colorimetric substrates are available, and also the green fluorescent proteins, luciferase [Stocker et al, 2003], alkaline phosphatase [Kohler et al, 2000] or, as recently proposed, carotenoid [Maeda et al, 2006] or pyocyanin [Fletcher et al, 2007] synthesis systems. Crucial criteria for choosing or building a biosensor include sensitivity, time needed, portability, robustness and eventual reusability.…”