New microscope big boost to research in N.Z.

Press, 12 November 1985, Page 17

New microscope big boost to research in N.Z.

By

DERRICK ROONEY

A new and extremely advanced electron microscope which may open new doors for biological research in New Zealand has just been installed on the D.S.I.R. campus at Lincoln. The instrument which with its bright orange central column looks more like something from a “Star Trek” control room than a microscope as most people know it, is a Zeiss EM 902,’ developed by the Carl Zeiss company with the sponsorship of the West German Ministry of Research and Technology. Only six have been sold in the world, and the Lincoln instrument is the first to come to the Southern Hemisphere. It cost $311,000. Dr Melva Philipson, who is supervising its installation and use at Lincoln, went to Germany earlier this year to be trained in using it and in analysing the data it provides.

The microscope uses 5.5 kw of electricity while magnifying the image of specimens up to 400,000 times. It has nearly doubled the possible magnification of the 20-year-old instrument which it replaced and even at the highest magnification produces consistently sharper images. It has a resolution down to 0.3 nanometres compared with 5 or 6 nanometres for the old instrument. A nanometre is one millionth of a millimetre. The instrument works by “firing” a beam of electrons through a specimen from an electron gun mounted at the top of the column. The different elements in the cells of the specimen permit differing amounts of energy to pass through, and when the beam has passed the specimen a magnetic spectrometer “sorts out” the electrons of different energy to create an image which is focused on the screen at the base of the column.

Because of this method it is relatively free of the “scattering” problem which occurs in other electron microscopes as a result of stray electrons causing blurring of the image. An advantage of the new instrument is that it is able to use unstained specimens, unlike a scanning electron microscope. It is also able to produce a much brighter and clearer image. Conventional scanning electron microscopes project an image by “reading” the electron beam from above as it hits the specimen and projecting the image on a screen, in manner rather similar to the way a television picture is built up. The new instrument analyses the beam after it has passed through the specimen and transmits the image directly to the screen. Zeiss describes the instrument as particularly suitable for such work as evaluating elemental compositions of tissues and cells. At Lincoln, it will be used for both pure research and applied research, and its use for applied research has already started. Dr Philipson is looking at ryegrass seeds to find out how the fungus which causes ryegrass staggers (a disease of sheep) is transmitted from one generation of grass to the next. This fungus is a tiny organism known as an endophyte — a fungus which lives inside a plant or seed. These are quite common and usually cause no harm either to the host or to the animals that eat it, but the ryegrass endophyte releases a toxin which causes the disease. A microscopic study of the way in which it creates the toxin may help plant breeders to raise a strain of grass which is immune to it. Other planned studies are aimed

at assembling knowledge which might help to breed a tear-free onion or protect bees against poisoning from karaka nectar. The karaka, a coastal tree possibly introduced originally by the Maoris, was widely planted by Maoris who used its nuts as food (after they had treated them to neutralise the poison in the fruit). Its nectar contains toxins which can kill bees. The microscopic study will localise these toxins in the cells of the nectaries.

“Onion tears” are caused by volatile substances known as precursors, which also give onions their characteristic sulphurous flavour. Analysis of the precursors to localise them in the plant cells will provide useful information for plant breeders, and may enable them to develop an onion which retains its flavours but doesn’t make the eyes water. This would have enormous potential as a horticultural crop. There will be many more projects. Microscope time will be available not only to the scientific community at Lincoln but to other researchers. The Ministry of Agriculture and Fisheries, which contributed towards its cost, will use it and so will the Wool Research Organisation.

Dr Philipson also hopes for support from agricultural and seed companies, especially for the ryegrass study. An image intensifier, costing about $60,000, would be a very useful accessory, she said, and she hopes to find a sponsor to provide one. Dr Philipson sees the instrument as a “focus for New Zealand electron microscopy.” “It is really going to be something for New Zealand,” she says. “There is still a lot not known about what it can do — we are a long way yet from a full understanding of its analytical uses.”