http://www.mdpi.com/journal/sensors/special_issues/microbial_biosensors/ Dear Colleagues, This issue is devoted to the field Microbial Biosensors ranging from detecting growth of microorganisms to the tracking of metabolic activity or drug resistance within microorganism based on nano/microtechnology. Contributions on the integration of the microbial biosensors in small form factor e.g. lab-on-chips are of high interest for this special issue. All types of applications using nano/microtechnology for on-line detection will be accepted. Prof. Dr. Martin HegnerGuest Editor{snippet name="submission_info"} http://www.mdpi.com/1424-8220/10/4/3562/ Methionine is an essential amino acid for animals and is typically considered one of the first limiting amino acids in animal feed formulations. Methionine deficiency or excess in animal diets can lead to sub-optimal animal performance and increased environmental pollution, which necessitates its accurate quantification and proper dosage in animal rations. Animal bioassays are the current industry standard to quantify methionine bioavailability. However, animal-based assays are not only time consuming, but expensive and are becoming more scrutinized by governmental regulations. In addition, a variety of artifacts can hinder the variability and time efficacy of these assays. Microbiological assays, which are based on a microbial response to external supplementation of a particular nutrient such as methionine, appear to be attractive potential alternatives to the already established standards. They are rapid and inexpensive in vitro assays which are characterized with relatively accurate and consistent estimation of digestible methionine in feeds and feed ingredients. The current review discusses the potential to develop Escherichia coli-based microbial biosensors for methionine bioavailability quantification. Methionine biosynthesis and regulation pathways are overviewed in relation to genetic manipulation required for the generation of a respective methionine auxotroph that could be practical for a routine bioassay. A prospective utilization of Escherichia coli methionine biosensor would allow for inexpensive and rapid methionine quantification and ultimately enable timely assessment of nutritional profiles of feedstuffs. http://www.mdpi.com/1424-8220/10/4/3562/ Thu, 08 Apr 2010 00:00:00 CEST Sensors 2010-04-08 10 4 Review 3562 3584 1424-8220 Potential for Development of an Escherichia coli—Based Biosensor for Assessing Bioavailable Methionine: A Review 2010-04-08 doi: 10.3390/s100403562 Vesela I. Chalova Clifford A. Froelich Steven C. Ricke http://www.mdpi.com/1424-8220/10/3/1846/ Piezoelectric DNA-based biosensor technology was developed as a new method for detection of M. tuberculosis. This method consists of immobilizing a thiol-modified oligonucleotide probe on the gold electrode surface of a quartz crystal, using a self-assembled monolayer method. The advantage of this study is that a non-amplified genomic bacterial DNA target was used. Instead, the genomic DNA was digested by restriction enzyme to obtain DNA fragments containing the target sequence. The fabricated biosensor was evaluated through an examination of 200 samples. No cross hybridization were observed against M. avium complex and other microorganisms. This target DNA preparation, without PCR amplification, will reduce time, costs, and the tedious step of amplification. http://www.mdpi.com/1424-8220/10/3/1846/ Tue, 09 Mar 2010 00:00:00 CET Sensors 2010-03-09 10 3 Article 1846 1858 1424-8220 Detection of Non-Amplified Mycobacterium tuberculosis Genomic DNA Using Piezoelectric DNA-Based Biosensors 2010-03-09 doi: 10.3390/s100301846 Thongchai Kaewphinit Somchai Santiwatanakul Chamras Promptmas Kosum Chansiri http://www.mdpi.com/1424-8220/10/2/1062/ Tree assessment methodologies, currently used to evaluate the structural stability of individual urban trees, usually involve a visual analysis followed by measurements of the internal soundness of wood using various instruments that are often invasive, expensive, or inadequate for use within the urban environment. Moreover, most conventional instruments do not provide an adequate evaluation of decay that occurs in the root system. The intent of this research was to evaluate the possibility of integrating conventional tools, currently used for assessments of decay in urban trees, with the electronic nose–a new innovative tool used in diverse fields and industries for various applications such as quality control in manufacturing, environmental monitoring, medical diagnoses, and perfumery. Electronic-nose (e-nose) technologies were tested for the capability of detecting differences in volatile organic compounds (VOCs) released by wood decay fungi and wood from healthy and decayed trees. Three e-noses, based on different types of operational technologies and analytical methods, were evaluated independently (not directly compared) to determine the feasibility of detecting incipient decays in artificially-inoculated wood. All three e-nose devices were capable of discriminating between healthy and artificially-inoculated, decayed wood with high levels of precision and confidence. The LibraNose quartz microbalance (QMB) e-nose generally provided higher levels of discrimination of sample unknowns, but not necessarily more accurate or effective detection than the AromaScan A32S conducting polymer and PEN3 metal-oxide (MOS) gas sensor e-noses for identifying and distinguishing woody samples containing different agents of wood decay. However, the conducting polymer e-nose had the greater advantage for identifying unknowns from diverse woody sample types due to the associated software capability of utilizing prior-developed, application-specific reference libraries with aroma pattern-recognition and neural-net training algorithms. http://www.mdpi.com/1424-8220/10/2/1062/ Fri, 29 Jan 2010 00:00:00 CET Sensors 2010-01-29 10 2 Article 1062 1092 1424-8220 Evaluation of Three Electronic Noses for Detecting Incipient Wood Decay 2010-01-29 doi: 10.3390/s100201062 Manuela Baietto Alphus D. Wilson Daniele Bassi Francesco Ferrini http://www.mdpi.com/1424-8220/10/1/330/ A biosensor is composed of a bioreceptor, an associated recognition molecule, and a signal transducer that can selectively detect target substances for analysis. DNA based biosensors utilize receptor molecules that allow hybridization with the target analyte. However, most DNA biosensor research uses oligonucleotides as the target analytes and does not address the potential problems of real samples. The identification of recognition molecules suitable for real target analyte samples is an important step towards further development of DNA biosensors. This study examines the characteristics of DNA used as bioreceptors and proposes a hybrid evolution-based DNA sequence generating algorithm, based on DNA computing, to identify suitable DNA bioreceptor recognition molecules for stable hybridization with real target substances. The Traveling Salesman Problem (TSP) approach is applied in the proposed algorithm to evaluate the safety and fitness of the generated DNA sequences. This approach improves efficiency and stability for enhanced and variable-length DNA sequence generation and allows extension to generation of variable-length DNA sequences with diverse receptor recognition requirements. http://www.mdpi.com/1424-8220/10/1/330/ Thu, 31 Dec 2009 00:00:00 CET Sensors 2009-12-31 10 1 Article 330 341 1424-8220 An Evolution Based Biosensor Receptor DNA Sequence Generation Algorithm 2009-12-31 doi: 10.3390/s100100330 Eungyeong Kim Malrey Lee Thomas M. Gatton Jaewan Lee Yupeng Zang http://www.mdpi.com/1424-8220/9/12/9741/ Anabaena sensory rhodopsin (ASR) is an archaeal-type rhodopsin found in eubacteria. The gene encoding ASR forms a single operon with ASRT (ASR transducer) which is a 14 kDa soluble protein, suggesting that ASR functions as a photochromic sensor by activating the soluble transducer. This article reviews the detailed photoreaction processes of ASR, which were studied by low-temperature Fourier-transform infrared (FTIR) and UV-visible spectroscopy. The former research reveals that the retinal isomerization is similar to bacteriorhodopsin (BR), but the hydrogen-bonding network around the Schiff base and cytoplasmic region is different. The latter study shows the stable photoproduct of the all-trans form is 100% 13-cis, and that of the 13-cis form is 100% all-trans. These results suggest that the structural changes of ASR in the cytoplasmic domain play important roles in the activation of the transducer protein, and photochromic reaction is optimized for its sensor function. http://www.mdpi.com/1424-8220/9/12/9741/ Thu, 03 Dec 2009 00:00:00 CET Sensors 2009-12-03 9 12 Review 9741 9804 1424-8220 Photoreactions and Structural Changes of Anabaena Sensory Rhodopsin 2009-12-03 doi: 10.3390/s91209741 Akira Kawanabe Hideki Kandori http://www.mdpi.com/1424-8220/9/12/9444/ We present circular architecture bioimplant strain sensors that facilitate a strong resonance frequency shift with mechanical deformation. The clinical application area of these sensors is for in vivo assessment of bone fractures. Using a rectangular geometry, we obtain a resonance shift of 330 MHz for a single device and 170 MHz for its triplet configuration (with three side-by-side resonators on chip) under an applied load of 3,920 N. Using the same device parameters with a circular isotropic architecture, we achieve a resonance frequency shift of 500 MHz for the single device and 260 MHz for its triplet configuration, demonstrating substantially increased sensitivity. http://www.mdpi.com/1424-8220/9/12/9444/ Wed, 25 Nov 2009 00:00:00 CET Sensors 2009-11-25 9 12 Article 9444 9451 1424-8220 Circular High-Q Resonating Isotropic Strain Sensors with Large Shift of Resonance Frequency under Stress 2009-11-25 doi: 10.3390/s91209444 Rohat Melik Emre Unal Nihan Kosku Perkgoz Christian Puttlitz Hilmi Volkan Demir http://www.mdpi.com/1424-8220/9/11/9147/ Whole-cell, genetically modified bioreporters are designed to emit detectable signals in response to a target analyte or related group of analytes. When integrated with a transducer capable of measuring those signals, a biosensor results that acts as a self-contained analytical system useful in basic and applied environmental, medical, pharmacological, and agricultural sciences. Historically, these devices have focused on signaling proteins such as green fluorescent protein, aequorin, firefly luciferase, and/or bacterial luciferase. The biochemistry and genetic development of these sensor systems as well as the advantages, challenges, and common applications of each one will be discussed. http://www.mdpi.com/1424-8220/9/11/9147/ Tue, 17 Nov 2009 00:00:00 CET Sensors 2009-11-17 9 11 Review 9147 9174 1424-8220 Reporter Proteins in Whole-Cell Optical Bioreporter Detection Systems, Biosensor Integrations, and Biosensing Applications 2009-11-17 doi: 10.3390/s91109147 Dan M. Close Steven Ripp Gary S. Sayler