Posts from November 2016

The Agricultural Research Service of the USDA uses a Quorum Cryo-SEM preparation system for the study of mites, ticks and other soft bodied organisms

Dr Gary Bauchan is the Director of the Electron and Confocal Microscopy Unit at the Agricultural Research Service (ARS), the principal in-house research agency of the United States Department of Agriculture. The Unit is a core facility with the responsibility of providing collaborative assistance to scientists from ARS, Northeast Area and Beltsville Agricultural Research Center (BARC) who have microscopy applications that require high resolution imaging. Dr Bauchan’s team have produced images using electron microscopes of bacteria, fungi, mites, insects, nematodes and parasites along with plant and animal tissues both healthy and diseased. One of his major collaborations is with Dr Ron Ochoa, the world’s expert on plant feeding mites.

Biological specimens require special treatment due to the high water content of the samples. Many of the specimens are in liquid cultures or are very soft-bodied and by using classical preparative techniques will either destroy the specimen or distort the specimen producing artefacts. A cryo-prep system is an ultra-fast method to ready the specimens for observation in a SEM especially a high resolution field emission SEM. Thus, specimens are frozen in time to allow for observation of feeding behaviour, mating behaviour, host/parasite interactions, etc. It preserves the natural orientation of ultrafine structures such as setae, antenna, legs, skin texture, sensory organs, waxy coatings and eggs.

Asked about his experience using a Quorum PP2000 Cryo-SEM preparation system on the Hitachi S-4700 field emission scanning electron microscope, Dr Bauchan said “The Quorum system is easy to use, the set-up for imaging is logical, durable, reliable, and maintains ultra-low temperatures for a long period of time. Holders containing pre-frozen samples are transferred into the cryo-prep chamber where they are etched to remove any surface contamination (condensed water vapour) by raising the temperature of the stage from -130 ºC to -90 °C for 10-15 minutes. Following etching, the temperature inside the chamber was lowered below -130 °C, and the specimens were coated with a 10 nm layer of platinum using a magnetron sputter head equipped with a platinum target. The specimens were transferred to a pre-cooled (-130 °C) cryo-stage in the SEM for observation.”

The system has been used in multiple projects by the Unit, many of which have been published with the generation of stunning, colourful images. The use of low temperature SEM has been shown time and again to be the best method for the examination of microscopic biological specimens and their ultrastructure. The work in conjunction with Dr Ochoa has been particularly productive with five papers published this year to date. These have focused on the field of acarology, a branch of zoology dealing with the study of mites and ticks.

Above image: Gary Bauchan, Director, Electron & Confocal Microscopy Unit, USDA-ARS inserts mite specimens into the Quorum PP2000 Cryo-Prep Chamber (photo courtesy of Steve Ausmus, USDA-ARS, d3713-1)

Mention of trade names or commercial products in this publication is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the USDA.

The Biomedical Imaging Unit at the University of Southampton uses Quorum coating system as a general purpose work station

The Biomedical Imaging Unit (BIU) is a core facility, which provides a diagnostic and research service in high quality/high resolution microscopy. It is a joint facility run for the benefit of, and jointly funded by, the University of Southampton and Southampton University Hospitals NHS Trust with eight full time staff.

The microscopes in the Biomedical Imaging Unit are used extensively for research, teaching and diagnostic work by staff and students across the Trust and University with some 100-150 users per year from most science faculties including Medicine, Physics, National Oceanographic Centre, Engineering and Biological Sciences. This nationally important unit is extremely well equipped with two new microscopes to enable it to do 3D microscopy in addition to the existing transmission and scanning electron microscopes, confocal and time lapse light microscopes, image analysis and video microscopes.

The Quorum Q150T ES coater was purchased to replace a very old (1960s vintage) Edwards coating unit. It is being used as a general purpose workstation for carbon coating, sputter coating for high resolution SEM, glow discharging grids, cleaning apertures etc.

Discussing the purchase, Anton Page, Head of the BIU, says, “We looked at various competitive systems but these did not fit our needs nor matched our price constraints. The new coater is ideal. It is a combined system providing both sputtering and carbon coating. The deposition heads can be swapped in seconds and the intelligent system logic automatically recognises which head is in place and displays the appropriate operating settings.”

“Furthermore, for us, it is very fast! Our old coating unit took half a day (really!) to pump down before we could use it. The Q150T ES is a turbo pump system and can do the same job in 10 – 15 mins and get a better result. Newer coating units are obviously also much quicker than our old one but this is much more versatile – it has interchangeable head inserts – one for carbon coating and one for sputter coating which prevents cross-contamination of specimens, making cleaning easier too. It is simple to use and so we can teach our users how to coat their specimens instead of doing it for them.”

The Quorum Q150T ES is one of a family of coaters designed for applications across the spectrum of electron microscopy. Thousands of Q150 and Q300 coaters are used in EM laboratories around the world - and increasingly for many thin film coating applications.

Patricia Goggin from the University of Southampton working with the Quorum Q150T ES coating system (l). A transmission electron micrograph of immuno-gold labelled amyloid beta fibrils (r) prepared by Savannah Lynn