Editor's note: Science Scan is a roundup of recently published biotechnology-relevant research.
In Texas 21 years ago, a cow went belly-up. Veterinarians attributed the bovine's demise in 1981 to infection by Bacillus anthracis - the anthrax bacterium.
This genomic strain of the pathogen was designated "Ames," for reasons now lost to history. In 1982, it was sent to the U.S. Army Medical Research Institute in Fort Detrick, Md., for use in the U.S. defensive biological weapons program.
In the fall of 2001, strange powder-laden envelopes containing lethal anthrax spores struck 11 human victims with inhalational anthrax - the most deadly form of the infection. Five of the 11 succumbed to the pulmonary infection. The first to die was a photo editor in Florida. It devolved upon The Institute for Genomic Research (TIGR), which was closing in on sequencing the total B. anthracis genome, to analyze and compare the Ames strain with the Florida isolate.
TIGR microbiologist and genomicist Timothy Read recalled: "We had the sequences of the Texas veterinary cow strain sent from Fort Detrick to England, to the Defense Science Laboratory of the UK Ministry of Defense."
Read is lead author of a paper in the current Sciencexpress, released online May 8, 2002, but dated May 10. It's title: "Comparative genome sequencing for discovery of novel polymorphisms in Bacillus anthracis."
"This paper is a description of the biology of anthrax based on its genome," Read told BioWorld Today. "We were working on the complete B. anthracis genome sequence from the strain in Porton Down, England. We're publishing that later this year. It will boost the efforts to develop new vaccines, drugs and detection methods.
"The sequence's base pairs total 5.2 million, and functionally known genes number 5.5 [thousand] to six thousand," Read noted. "It has one large chromosome and two small, circular plasmids. The lethal toxin is carried on one plasmid of the two," he continued. "The other carries a capsule that's involved in the invasion by anthrax of the immune system. Those are key components of virulence. We found 60 marker differences, comparing the Florida strain against Porton chromosomes - and also against previously published plasmids. These DNA differences include SNPs [single nucleotide polymorphisms], indels and tandem repeats.
"Indels," he explained, "are genetic jargon. If you compare two sequences, you find one has two more bases than the other, and you can't tell without further information whether those two bases are insertions in one strain or deletions in the other. So we call that event an indel. It's a DNA difference. Tandem repeats are where you have a repeated DNA sequence, which is adjacent to another repeat - as opposed to having the iteration in another location of the chromosome. It means any DNA sequence that's repeated in tandem.
"And by comparative genomics," Read pointed out, "you can find additional markers - differences in SNP deletions that can possibly be used to distinguish between B. anthracis strain isolates. Our overall finding is that you can compare two Bacillus anthracis strains by this genome-wide genotyping scheme. It's identical to DNA fingerprinting.
"We've shown," he observed, "that this is a legitimate technique to use in forensic investigations of bioterror attacks. And probably with the likely decrease in sequencing costs in the future, this type of approach could be used more frequently for forensic investigation - not only in bacteria but in humans. Anything that had DNA in it."
However, Read allowed, "In terms of being able to detect whether a powder is anthrax, it's not the most useful technique." A related editorial in Science carries the headline: "Useful data but no smoking gun."
Not By Brain Alone, Circadian Rhythms Site Timepiece Genes Throughout Organs Of Body
The body's daily rhythms, a beat thought to be conducted by a master clock sited in the brain, may actually be driven by tiny timepieces tucked all over the body. What's more, these peripheral tickers keep their own time. Thus, watches pocketed in the liver and heart apparently use different genes to perform the same oscillating bodily functions. An article in Nature released online April 21, 2002, reports: "Extensive and divergent circadian gene expression in liver and heart." Its authors are neurobiologists at Harvard Medical School.
It's no news that organs work at different rates - the heart beats, the kidneys traffic ions and electrolytes, the liver metabolizes nutrients variably during the day. This knowledge enables more effective drug regimens for patients.
Using gene chips, the authors monitored the activity of 12,488 genes - one-third the entire mouse genome - in the hearts and livers of mice at various time points during the day. Of more than 460 heart genes and nearly 600 liver genes, they found only 37 circadian genes striking the hours in common. Many had originally been discovered in the brain's Big Ben suprachiasmatic nucleus.
Though different in composition, the gene sets were all performing remarkably similar tasks in cells - communication, transport, metabolism, blood pressure and apoptosis (cell death). The reason for that complexity needs further work.
Sons Shorten Their Mothers' Lives; Daughters Pay For Themselves In Maternal Longevity
Can having sons take years off mothers' lives? A Finish demographic study found that compared to having daughters, giving birth to sons shortened the mothers' life span by an average of 34 weeks per boy born. Scientists at the University of Turku pored over church records from 1640 to 1870, to see how mothers' longevity was affected by the number of sons and daughters they delivered and raised. Their report in Science, dated May 10, 2002, is titled: "Sons reduced maternal longevity in preindustrial humans."
The number of daughters born did not have a statistically significant effect, but the number of girls raised to womanhood exerted a positive influence that was stronger than the negative effect of raising boys to manhood. The authors propose that giving birth to sons put more stress on the maternal body than does having daughters, and that the latter helped prolong their mothers' lives in that pre-modern era by helping with everyday tasks.