Featured Research

from universities, journals, and other organizations

Discovery Of Size Changes Of Bacillus Spores May Lead To Simpler, Faster Anthrax Detector

Date:
February 11, 2003
Source:
University Of California - Berkeley
Summary:
The spores of a microbe closely related to anthrax swell with increasing humidity - a physical change that might allow quick and cheap detection of Bacillus spores like anthrax, according to physicists at the University of California, Berkeley.

Berkeley - The spores of a microbe closely related to anthrax swell with increasing humidity - a physical change that might allow quick and cheap detection of Bacillus spores like anthrax, according to physicists at the University of California, Berkeley.

Related Articles


The swelling is a surprise to microbiologists, who have assumed that spores of the Bacillus bacteria, which include anthrax (Bacillus anthracis), are a dormant, resting and basically inert stage of the microbe.

The swelling, observed of spores of Bacillus thuringiensis, bacteria now often used to kill insects that attack crops, may be diagnostic of all Bacillus spores and may allow scientists to distinguish between different types of Bacillus.

"If we are able to discriminate between spores based on size or swelling characteristics, it's a test we could do in seconds to minutes," said Andrew J. Westphal, a research physicist at UC Berkeley's Space Sciences Laboratory.

Westphal and UC Berkeley physics professor P. Buford Price, along with microbial biologists Terrance J. Leighton and Katherine E. Wheeler of the Children's Hospital Oakland Research Institute, will report their findings next week in the online early edition of the Proceedings of the National Academy of Sciences. The article will be posted on the Web sometime during the week of Feb. 10.

On Jan. 22, the federal government began to deploy environmental monitors to detect airborne bioterrorism agents, including anthrax and smallpox. The system relies on filtering air and sending the filters to a lab, where any attached microbes would be cultured and identified. Even with advanced techniques such as PCR (polymerase chain reaction) to detect microbial genes, the turnaround time would be 12-24 hours.

A device to scan for Bacillus spores of a certain size and swelling time could provide an answer in about 10 minutes.

"This wouldn't be a foolproof way of saying, "You've got anthrax spores,'" added Price, "but it would be a flag for you to go to the next step, perhaps a PCR test to detect anthrax DNA."

The new technique also could mark a significant advance in biological imaging.

"The technology that Price and Westphal have developed is quite extraordinary," said Leighton, an anthrax expert and UC Berkeley professor emeritus of molecular and cell biology. "The holy grail in microbiology at this moment is trying to manipulate and image single microbial cells, because they are at the limit of resolution of normal optical microscopes. This technology pushes the lower limit of resolving power by perhaps a factor of 100 beyond what has been demonstrated previously, so you can see much more fine structure and gather much more information about the shape and the response of the single cell."

Price and Westphal first considered using size to discriminate between Bacillus spores, more properly called endospores, after anthrax spores began showing up in mail at spots around the East Coast. Both physicists had experience measuring microscopic objects during more than a decade spent searching for the minuscule tracks of cosmic rays in special glasses and of interplanetary dust grains in aerogels, and more recently, searching for unusual microbes in Greenland and Antarctic ice.

In researching what is known about spore size, they found that most measurements have been very rough and have not taken account of humidity or other environmental factors. The lack of data is due partly to the spores' size. With diameters of around two microns - about one-hundredth the width of a human hair - they are smaller than the resolution limit of most light microscopes, so precise measurements are not easy. More precise electron microscope images can only be taken of thin sections of spores in a vacuum, eliminating any possibility of gauging the effect of humidity.

About 10 years ago, the two developed a technique to extract more precision from optical microscope measurements. Using a microscope with attached CCD camera - a basic camcorder - Westphal takes hundreds to thousands of snapshots of an object. Each image is slightly offset from the others, allowing him to average the sizes to obtain a more precise measure of the object's size, often to within one-hundredth the width of a single pixel.

In practice, an automated microscope rapidly scans a surface, measuring and recording the size of every object and fitting it to the shape of an ellipse. The absolute precision of a single measurement is better than 50 nanometers, or just two percent of a micron. By measuring the same object multiple times, the precision can be improved by a factor of 10, to better than 5 nanometers.

"We are taking advantage of modern electronics and image processing to look at the size of individual spores with very high time resolution and rapid analysis," Westphal said.

In their first attempts, they found that the spores of four types of Bacillus differed significantly in size - enough to let them distinguish each by size alone. The four were B. cereus, which can cause food poisoning; the insecticidal B. thuringiensis; and two harmless soil bacteria, B. subtilis and B. megaterium.

To determine whether spores change size with environmental conditions, they checked the size of B. thuringiensis spores under varying levels of humidity. To their surprise, spores swelled significantly - about 4 percent - under conditions of high humidity. The swelling took place in two stages - spores swelled about 2.9 percent in less than 50 seconds, and then increased another 0.9 percent after about eight minutes.

Price and Westphal interpret this as rapid water diffusion into the spore's outer coat and cortex, followed by slower diffusion into the core. When subjected to a dry environment, the spores shrink.

The swelling with humidity may explain why spores are more susceptible to being killed by gases such as formaldehyde, ethylene oxide and chlorine dioxide in conditions of high humidity. A larger, swollen spore has larger pores to admit more gas.

"This paper provides at least one potential mechanism or basis for why, with higher levels of humidity, one sees greater efficacy of spore killing," Leighton said. "That is very important for decontamination, whether it's medical instrument sterilization, building decontamination or removing toxic mold. It's a fundamentally important observation."

Price also noted that the reaction of spores to humidity could be a precursor to germination, which typically occurs in the presence of water and nutrients. By swelling, spores may be priming themselves to quickly germinate when food becomes available.

More research needs to be done before the technique can be adapted to detection and identification of species of Bacillus spores, Price emphasized. He and Westphal are planning to study the size of spores grown under different conditions and test whether spore agglomeration interferes with the measurement of individual spore size. Westphal thinks that agglomeration will not be a problem, because he was able to measure the sizes of individual spores from Mosquito Dunks, a commercial preparation of compressed B. thuringiensis spores used to control mosquito larvae.

They also plan to study defanged anthrax spores to determine whether, like the other Bacillus strains, they have a distinctive size and reaction to humidity.

The work was funded by the National Science Foundation.


Story Source:

The above story is based on materials provided by University Of California - Berkeley. Note: Materials may be edited for content and length.


Cite This Page:

University Of California - Berkeley. "Discovery Of Size Changes Of Bacillus Spores May Lead To Simpler, Faster Anthrax Detector." ScienceDaily. ScienceDaily, 11 February 2003. <www.sciencedaily.com/releases/2003/02/030211072729.htm>.
University Of California - Berkeley. (2003, February 11). Discovery Of Size Changes Of Bacillus Spores May Lead To Simpler, Faster Anthrax Detector. ScienceDaily. Retrieved October 26, 2014 from www.sciencedaily.com/releases/2003/02/030211072729.htm
University Of California - Berkeley. "Discovery Of Size Changes Of Bacillus Spores May Lead To Simpler, Faster Anthrax Detector." ScienceDaily. www.sciencedaily.com/releases/2003/02/030211072729.htm (accessed October 26, 2014).

Share This



More Plants & Animals News

Sunday, October 26, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Deep Sea 'mushroom' Could Be Early Branch on Tree of Life

Deep Sea 'mushroom' Could Be Early Branch on Tree of Life

Reuters - Innovations Video Online (Oct. 24, 2014) Miniature deep sea animals discovered off the Australian coast almost three decades ago are puzzling scientists, who say the organisms have proved impossible to categorise. Academics at the Natural History of Denmark have appealed to the world scientific community for help, saying that further information on Dendrogramma enigmatica and Dendrogramma discoides could answer key evolutionary questions. Jim Drury has more. Video provided by Reuters
Powered by NewsLook.com
Black Bear Cub Goes Sunday Shopping

Black Bear Cub Goes Sunday Shopping

Reuters - Light News Video Online (Oct. 23, 2014) Price check on honey? Bear cub startles Oregon drugstore shoppers. Rough Cut (no reporter narration). Video provided by Reuters
Powered by NewsLook.com
Dances With Wolves in China's Wild West

Dances With Wolves in China's Wild West

AFP (Oct. 23, 2014) One man is on a mission to boost the population of wolves in China's violence-wracked far west. The animal - symbol of the Uighur minority there - is under threat with a massive human resettlement program in the region. Duration: 00:41 Video provided by AFP
Powered by NewsLook.com
Breakfast Debate: To Eat Or Not To Eat?

Breakfast Debate: To Eat Or Not To Eat?

Newsy (Oct. 23, 2014) Conflicting studies published in the same week re-ignited the debate over whether we should be eating breakfast. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Plants & Animals

Earth & Climate

Fossils & Ruins

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins