Microbial biosensors.

Division of Chemical and Biomolecular Engineering and Centre of Biotechnology, Nanyang Technological University, Singapore 637722, Singapore.
Analytica chimica acta (Impact Factor: 4.31). 06/2006; 568(1-2):200-10. DOI: 10.1016/j.aca.2005.11.065
Source: PubMed

ABSTRACT A microbial biosensor is an analytical device that couples microorganisms with a transducer to enable rapid, accurate and sensitive detection of target analytes in fields as diverse as medicine, environmental monitoring, defense, food processing and safety. The earlier microbial biosensors used the respiratory and metabolic functions of the microorganisms to detect a substance that is either a substrate or an inhibitor of these processes. Recently, genetically engineered microorganisms based on fusing of the lux, gfp or lacZ gene reporters to an inducible gene promoter have been widely applied to assay toxicity and bioavailability. This paper reviews the recent trends in the development and application of microbial biosensors. Current advances and prospective future direction in developing microbial biosensor have also been discussed.

  • [Show abstract] [Hide abstract]
    ABSTRACT: A biochemical oxygen demand (BOD) biosensor for effective and expeditious BOD(7) estimations was constructed and the non-steady phase of the output signal was extensively studied. The modelling approach introduced allows response curve reconstruction and a curve fitting procedure of good quality, resulting in parameters indicating the relationship between response and organic substrate concentration and stability properties of the BOD biosensor. Also, the immobilization matrixes of different thicknesses were characterized to determine their suitability for bio-sensing measurements in non-stationary conditions, as well as for the determination of the mechanical durability of the BOD biosensor in time. The non-steady response of the experimental output of the BOD biosensor was fitted according to the developed model that enables to determine the stability of the biosensor output and dependency on biodegradable organic substrate concentration. The calibration range of the studied BOD biosensor in OECD synthetic wastewater was 15-110 mg O(2) L(-1). Repeatability tests showed relative standard deviation (RSD) values of 2.8% and 5.8% for the parameter τ(d), characterizing the transient output of the amperometric oxygen sensor in time, and τ(s), describing the dependency of the transient response of the BOD biosensor on organic substrate concentration, respectively. BOD biosensor experiments for the evaluation of the biochemical oxygen demand of easily degradable and refractory municipal wastewater showed good concurrence with traditional BOD(7) analysis.
    Journal of Environmental Monitoring 11/2010; 13(1):95-100. · 2.09 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The aim of this review is to describe and discuss the concepts that have been employed to interpret N mineralization–immobilization in soil, and how N turnover is related to the characteristics of organic N and the biota conducting the transformations. A brief survey of the period before the arrival of electronic searches became available provides access to the classical literature that can help interpret today's challenges. Classical (acid hydrolysis) and modern spectrometry and spectroscopy techniques indicate that protein N is the prevalent component of organic N in soil. The presence of heterocyclic N can indicate its abiotic, partial synthesis as in fire-affected soils. Clays and pedogenic oxides can protect organic N against microbial degradation. The evidence for such protection is mostly based on in vitro studies involving pure clays, and proteins and their relevance to field conditions requires further work. The proteomic approach, with extraction and characterization of proteins stabilised by soil colloids (structural proteomics) might give further insights into this area. Functional proteomics can improve our understanding of the degradation of organic pollutants and organic debris as well as identifying the molecular colloquia between microorganisms and between soil biota and plant roots. Subdivision of organic N into sub-pools has helped to interpret mechanistic studies and modelling of N dynamics. Uncomplexed organic matter, obtained by physical fractionation procedures, is considered a labile pool. The interpretation of N mineralization measurements is affected by immobilization during microbial attack especially in high-C environments. Transfer of materials among particle size fractions and changes in microbiological properties of aggregates also can occur during fractionation procedures. Classical mineralization–immobilization turnover (MIT) does not always occur since microorganisms (and plants) can take up amino acid N with intracellular deamination. Protozoa, due to their grazing activities, can influence not only N mineralization but also the composition of rhizosphere–plant growth stimulating communities. Differences between N-poor and N-rich microsites, occurring in the same soil, can markedly affect the competition for N between plants and microorganisms especially the nitrifiers. The use of molecular techniques has allowed the identification of unculturable microorganisms and functional genes in the N cycle. Archeae are probably capable of oxidising NH4+ to NO3− and anerobic ammonia oxidation (Ammonox) bacteria have been identified in biofilms and probably also occur in soils. The use of nitrate as an electron acceptor is encoded by specific gene clusters but nitrate reduction also occurs in dissimilatory nitrate reduction.
    Soil Biology and Biochemistry. 01/2009;
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Soil is the ultimate sink for most contaminants and rarely has only a single contaminant. More than is generally acknowledge, environmental pollutants exist as mixtures (organic-organic, inorganic-inorganic, and organic-inorganic). It is much more difficult to study chemical mixtures than individual chemicals, especially in the complex soil environment. Similarly, understanding the toxicity of a chemical mixture on different microbial species is much more complex, time consuming and expensive, because multiple testing designs are needed for an increased array of variables. Therefore, until now, scientific enquiries worldwide have extensively addressed the effects of only individual pollutants toward nontarget microorganisms. In this review, we emphasize the present status of research on (i) the environmental occurrence of pollutant mixtures; (ii) the interactions between pollutant mixtures and ecologically beneficial microorganisms; and (iii) the impact of such interactions on environmental quality. We also address the limitations of traditional cultivation based methods for monitoring the effects of pollutant mixtures on microorganisms. Long-term monitoring of the effects of pollutant mixtures on microorganisms, particularly in soil and aquatic ecosystems, has received little attention. Microbial communities that can degrade or can degrade or can develop tolerance to, or are inhibited by chemical mixtures greatly contribute to resilience and resistance in soil environments. We also stress in this review the important emerging trend associated with the employment of molecular methods for establishing the effects of pollutant mixtures on microbial communities. There is currently a lack of sufficient cogent toxicological data on chemical mixtures for making informed decision making in risk assessment by regulators. Therefore, not only more toxicology information on mixtures is needed but also there is an urgent need to generate sufficient, suitable, and long-term modeling data that have higher predictability when assessing pollutant mixture effects on microorganisms. Such data would improve risk assessment at contaminated sites and would help devise more effective bioremediation strategies.
    Reviews of environmental contamination and toxicology 01/2011; 211:63-120. · 4.13 Impact Factor

Full-text (2 Sources)

Available from
May 23, 2014