A Microbial Sensor Based onPseudomonas putidafor Phenol, Benzoic Acid and Their Monochlorinated Derivatives Which Can Be Used in Water andn-Hexane

Microbial sensor for drug susceptibility testing of Mycobacterium tuberculosis

AIMS

Drug susceptibility testing (DST) of clinical isolates of Mycobacterium tuberculosis is critical in treating tuberculosis. We demonstrate the possibility of using a microbial sensor to perform DST of M. tuberculosis and shorten the time required for DST.

METHODS AND RESULTS

The sensor is made of an oxygen electrode with M. tuberculosis cells attached to its surface. This sensor monitors the residual oxygen consumption of M. tuberculosis cells after treatment with anti-TB drugs with glycerine as a carbon source. In principle, after drug pretreatment for 4-5 days, the response differences between the sensors made of drug-sensitive isolates are distinguishable from the sensors made of drug-resistant isolates. The susceptibility of the M. tuberculosis H37Ra strain, its mutants and 35 clinical isolates to six common anti-TB drugs: rifampicin, isoniazid, streptomycin, ethambutol, levofloxacin and para-aminosalicylic acid were tested using the proposed method. The results agreed well with the gold standard method (LJ) and were determined in significantly less time. The whole procedure takes approximately 11 days and therefore has the potential to inform clinical decisions.

CONCLUSIONS

To our knowledge, this is the first study that demonstrates the possible application of a dissolved oxygen electrode-based microbial sensor in M. tuberculosis drug resistance testing. This study used the microbial sensor to perform DST of M. tuberculosis and shorten the time required for DST.

SIGNIFICANCE AND IMPACT OF THE STUDY

The overall detection result of the microbial sensor agreed well with that of the conventional LJ proportion method and takes less time than the existing phenotypic methods. In future studies, we will build an O₂ electrode array microbial sensor reactor to enable a high-throughput drug resistance analysis.

Electrical wiring of Pseudomonas putida and Pseudomonas fluorescens with osmium redox polymers

Two different flexible osmium redox polymers; poly(1-vinylimidazole)12-[Os-(4,4'-dimethyl-2,2'-di'pyridyl)2Cl2](2+/+) (osmium redox polymer I) and poly(vinylpyridine)-[Os-(N,N'-methylated-2,2'-biimidazole)3](2+/3+) (osmium redox polymer II) were investigated for their ability to efficiently "wire" Pseudomonas putida ATCC 126633 and Pseudomonas fluorescens (P. putida DSM 6521), which are well-known phenol degrading organisms, when entrapped onto cysteamine modified gold electrodes. The two Os-polymers differ in redox potential and the length of the side chains, where the Os(2+/3+)-functionalities are located. The bacterial cells were adapted to grow in the presence of phenol as the sole source of organic carbon. The performance of the redox polymers as mediators was investigated for making microbial sensors. The analytical characteristics of the microbial sensors were evaluated for determination of catechol, phenol and glucose as substrates in both batch analysis and flow analysis mode.

Amperometric biosensors for detection of phenol using chemically modified electrodes containing immobilized bacteria

Eight strains of Pseudomonas were studied for development of phenol sensor. The immobilization of cells was performed by absorbing them on the working part of mediator-modified screen-printed electrodes (SPEs). Only three Pseudomonas strains were able to transfer electrons resulting from specific oxidation of phenol to the electrode by means of mediators; ferrocene, duroquinone and dimethyferrocene were successfully used with the strains 394 (p20), 74-III and 83-IV (working names), respectively. The lower limits for detection of phenol were 1 micro M for the strain 74-III and 10 micro M for the strain 83-IV and 394 (p20). Calibrations were obtained as the dependencies of logarithm of current changes (log deltaI) on logarithm of concentration (logC), log delta I vs. logC. Among all substrates tested (phenol, catechol, hydroquinone, ethanol, methanol, propanol, isopropanol, isobutanol, isoamylalcohol, acetate, glucose, xylose, vanillin, 2,4,6-trichlorphenol, 2,3,6-trichlorphenol, 4-hydroxy-3-methoxybenzoic acid, coumarin, pentafluorophenol), bacterial sensor demonstrated a good selectivity with respect to phenol and lower responses to catechol and hydroquinone (10-times lower). The dependence of signals on operating conditions was studied. The biosensor should be used during the day of preparation. The operational stability was satisfactory to perform up to 10 consecutive measurements. Low cost and very simple manufacturing procedure allow for bacterial sensor to be applied as disposable devices.

Microbial sensors on a respiratory basis for wastewater monitoring

In respect of their rapidity, their online capabilities, and their moderate costs, biosensing systems generally offer an attractive alternative to the existing methods of water analysis. Additionally, one particular advantage of microbial biosensors is the ability to measure direct effects on living cells, e.g., their respiratory activity and its alteration caused by environmental pollutants. It is true that microbial sensors, often do not provide the optimum solution for the determination of individual analytes when compared to established physico-chemical analysis methods. However, these biosensing devices are predestined for the summary determination of environmentally relevant compounds and their complex effects, respectively. For this reason, microbial sensors allow an integral evaluation of the degree of environmental pollution including the interaction of various compounds. Moreover, in some cases specific metabolic pathways in microorganisms are used, resulting in the development of microbial sensors for the more selective analysis for those compounds or pollutants, which cannot be measured by simple enzyme reactions, e.g., the determination of aromatic compounds and heavy metals. This chapter gives an overview of microbiological biosensors on respiratory basis for the measurement of the following environmentally relevant compounds: inorganic N-compounds, heavy metals, organic xenobiotics and the estimation of sum parameters or so-called complex parameters such as BOD, ADOC, N-BOD, and the inhibition of nitrification.