Analyzing the cells in various body fluids can greatly deepen the understanding of the mechanisms governing the cellular physiology. Due to the variability of physiological and metabolic states, it is important to be able to perform such studies on individual cells. Therefore, we developed an optofluidic system in which we precisely manipulated and monitored individual cells of Escherichia coli. We tested optical micromanipulation in a microfluidic chamber chip by transferring individual bacteria into the chambers. We then subjected the cells in the chambers to antibiotic cefotaxime and we observed the changes by using time-lapse microscopy. Separately, we used laser tweezers Raman spectroscopy (LTRS) in a different micro-chamber chip to manipulate and analyze individual cefotaxime-treated E. coli cells. Additionally, we performed conventional Raman micro-spectroscopic measurements of E. coli cells in a micro-chamber. We found observable changes in the cellular morphology (cell elongation) and in Raman spectra, which were consistent with other recently published observations. The principal component analysis (PCA) of Raman data distinguished between the cefotaxime treated cells and control. We tested the capabilities of the optofluidic system and found it to be a reliable and versatile solution for this class of microbiological experiments.

• Keywords
• E. coli, Raman micro-spectroscopy, antibiotics, optical tweezers, opto-fluidics,
• MeSH
• Principal Component Analysis MeSH
• Anti-Bacterial Agents adverse effects   MeSH
• Escherichia coli drug effects   growth & development   MeSH
• Lab-On-A-Chip Devices * MeSH
• Micromanipulation methods   MeSH
• Optical Tweezers * MeSH
• Spectrum Analysis, Raman MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Anti-Bacterial Agents MeSH

Baker's yeast (Saccharomyces cerevisiae) represents a very popular single-celled eukaryotic model organism which has been studied extensively by various methods and whose genome has been completely sequenced. It was also among the first living organisms that were manipulated by optical tweezers and it is currently a frequent subject of optical micromanipulation experiments. We built a microfluidic system for optical trapping experiments with individual cells and used it for the assessment of cell tolerance to phototoxic stress. Using optical tweezers with the wavelength of 1064 nm, we trapped individual Saccharomyces cerevisiae cells for 15 min and, subsequently, observed their stress response in specially designed microfluidic chambers over time periods of several hours by time-lapse video-microscopy. We determined the time between successive bud formations after the exposure to the trapping light, took account of damaged cells, and calculated the population doubling period and cell areas for increasing trapping power at a constant trapping time. Our approach represents an attractive, versatile microfluidic platform for quantitative optical trapping experiments with living cells. We demonstrate its application potential by assessing the limits for safe, non-invasive optical trapping of Saccharomyces cerevisiae with infrared laser light.

• Keywords
• Saccharomyces cerevisiae, laser, microfluidics, optical trapping, phototoxicity,
• MeSH
• Microfluidics MeSH
• Micromanipulation MeSH
• Optical Tweezers MeSH
• Saccharomyces cerevisiae * MeSH
• Publication type
• Journal Article MeSH

Algal biomass that is represented mainly by commercially grown algal strains has recently found many potential applications in various fields of interest. Its utilization has been found advantageous in the fields of bioremediation, biofuel production and the food industry. This paper reviews recent developments in the analysis of algal biomass with the main focus on the Laser-Induced Breakdown Spectroscopy, Raman spectroscopy, and partly Laser-Ablation Inductively Coupled Plasma techniques. The advantages of the selected laser-based analytical techniques are revealed and their fields of use are discussed in detail.

• MeSH
• Equipment Failure Analysis MeSH
• Biomass * MeSH
• Equipment Design MeSH
• Eukaryota cytology   growth & development   MeSH
• Lasers * MeSH
• Water Microbiology * MeSH
• Environmental Monitoring instrumentation   MeSH
• Spectrum Analysis instrumentation   MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Review MeSH