Manipulation Of Bacteria Research Articles

Microfluidic Sampling and Biosensing Systems for Foodborne Escherichia coli and Salmonella.

Developments of portable biosensors for field-deployable detections have been increasingly important to control foodborne pathogens in regulatory environment and in early stage of outbreaks. Conventional cultivation and gene amplification methods require sophisticated instruments and highly skilled professionals; while portable biosensing devices provide more freedom for rapid detections not only in research laboratories but also in the field; however, their sensitivity and specificity are limited. Microfluidic methods have the advantage of miniaturizing instrumental size while integrating multiple functions and high-throughput capability into one streamlined system at low cost. Minimal sample consumption is another advantage to detect samples in different sizes and concentrations, which is important for the close monitoring of pathogens at consumer end. They improve measurement or manipulation of bacteria by increasing the ratio of functional interface of the device to the targeted biospecies and in turn reducing background interference. This article introduces the major active and passive microfluidic devices that have been used for bacteria sampling and biosensing. The emphasis is on particle-based sorting/enrichment methods with or without external physical fields applied to the microfluidic devices and on various biosensing applications reported for bacteria sampling. Three major fabrication methods for microfluidics are briefly discussed with their advantages and limitations. The applications of these active and passive microfluidic sampling methods in the past 5 years have been summarized, with the focus on Escherichia coli and Salmonella. The current challenges to microfluidic bacteria sampling are caused by the small size and nonspherical shape of various bacterial cells, which can induce unpredictable deviations in sampling and biosensing processes. Future studies are needed to develop rapid prototyping methods for device manufacturing, which can facilitate rapid response to various foodborne pathogen outbreaks.

Nanoscale optical trap for fluorescent nanoparticles

Optical trapping has offered new potentialities in the manipulation of bacteria, living cells, organelles, or microparticles in micrometric volumes. Its extension to the nanometer scale may create exceptional opportunities in many areas of science. We report here the trapping of a single 100 nm radius particle in a nanometric volume. The trapping relies on stimulated emission of the fluorescent particle in the evanescent wave of a totally reflected Arago spot on a glass-liquid interface. The trapping volume is a 200 nm height and 125 nm radius cylinder. Such a nano-trap, aside from applications in nano-physics, may echo the needs of life scientists to manipulate ever-smaller biological samples.

Programmed Lab Experiments for Biochemical Investigation of Quorum-Sensing Signal Molecules in Rhizospheric Soil Bacteria.

Biochemistry courses in the Department of Molecular Biology at the National University of Río Cuarto, Argentina, are designed for undergraduate students in biology, microbiology, chemistry, agronomy, and veterinary medicine. Microbiology students typically have previous coursework in general, analytical, and organic chemistry. Programmed sequences of lab experiments allow these students to investigate biochemical problems whose solution is feasible within the context of their knowledge and experience. We previously designed and reported a programmed lab experiment that familiarizes microbiology students with techniques for detection and characterization of quorum-sensing (QS) and quorum-quenching (QQ) signal molecules. Here, we describe a sequence of experiments designed to expand the understanding and capabilities of biochemistry students using techniques for extraction and identification of QS and QQ signal molecules from peanut rhizospheric soil bacteria, including culturing and manipulation of bacteria under sterile conditions. The program provides students with an opportunity to perform useful assays, draw conclusions from their results, and discuss possible extensions of the study. © 2016 by The International Union of Biochemistry and Molecular Biology, 44:256-262, 2016.

Living Liquid Crystals

Bio-mechanical hybrids are an emerging class of engineered composite soft materials with the ability to move and reconfigure their structure and properties in response to external stimuli. Similar to their biological counterparts, they can transduce energy stored in the environment to drive systematic movements. This functionality is critical for a variety of applications, from bioinspired micromachines and sensors to self-assembled microrobots. Here, by combining two seemingly incompatible concepts, living swimming bacteria and inanimate but orientationally ordered lyotropic liquid crystal, we conceive a fundamentally new class of matter - living liquid crystals (LLCs). LLCs can be actuated and controlled by the amount of oxygen available to bacteria, by concentration of ingredients or by the temperature. Our studies reveal a wealth of intriguing phenomena, caused primarily by the coupling between the activity-triggered flows and director reorientations. Among these are (a) coupling between the orientation and degree of order of LLC and the bacterial motion, (b) local nematic-isotropic phase transition caused by the bacteria-produced shear flows, (c) periodic stripe instabilities of the director in surface-anchored LLCs, (d) director pattern evolution into an array of disclinations with positive and negative topological charges as the surface anchoring is weakened or when the bacterial activity is enhanced; (e) direct optical visualization and quantitative characterization of microflows generated by the nanometers-thick bacterial flagella by the birefringent LLC medium. Our work suggests an unorthodox design concept of reconfigurable microfluidic chambers for control and manipulation of bacteria. Besides an obvious importance to active matter, our studies can result in valuable biosensing and biomedical applications.

Two-component systems in Streptomyces: key regulators of antibiotic complex pathways

Streptomyces, the main antibiotic-producing bacteria, responds to changing environmental conditions through a complex sensing mechanism and two-component systems (TCSs) play a crucial role in this extraordinary “sensing” device.Moreover, TCSs are involved in the biosynthetic control of a wide range of secondary metabolites, among them commercial antibiotics. Increased knowledge about TCSs can be a powerful asset in the manipulation of bacteria through genetic engineering with a view to obtaining higher efficiencies in secondary metabolite production. In this review we summarise the available information about Streptomyces TCSs, focusing specifically on their connections to antibiotic production.

The Leeuwenhoek Lecture, 1981. The biochemical and genetic approach to the study of bioenergetics with the use of Escherichia coli: progress and prospects.

How the 'energy currency' of the cell, adenosine triphosphate (ATP), is produced consequent upon the oxidation of foodstuffs (oxidative phosphorylation) is, despite prolonged research, still a matter of debate and the molecular mechanism of the process is unknown. It appears that the problem of oxidative phosphorylation can be approached with the aid of the biochemical genetics of the bacterium Escherichia coli. The ease of manipulation of bacteria and definitive results obtained by this approach have been invaluable in solving other major biochemical problems. Mutants affected in oxidative phosphorylation have been isolated and characterized by genetic and biochemical techniques. These 'unc' mutants are affected in the adenosine triphosphatase (ATPase) multiprotein complex which is part of the cell membrane and responsible for the terminal stages of ATP synthesis. Seven distinct genes concerned with oxidative phosphorylation have been characterized in E. coli and shown to be part of an operon. The relationships between the different classes of unc genes and the various components of the ATPase have been established. Information about the assembly of the ATP synthesizing complex in the cell membrane has also been obtained and the stage set for further studies on the assembly, control and function of the ATP synthesizing system.